| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Development.Shakers
Description
Shake helpers.
Synopsis
- seq :: a -> b -> b
- filter :: (a -> Bool) -> [a] -> [a]
- zip :: [a] -> [b] -> [(a, b)]
- fst :: (a, b) -> a
- snd :: (a, b) -> b
- otherwise :: Bool
- ($) :: (a -> b) -> a -> b
- fromIntegral :: (Integral a, Num b) => a -> b
- realToFrac :: (Real a, Fractional b) => a -> b
- guard :: Alternative f => Bool -> f ()
- join :: Monad m => m (m a) -> m a
- class Bounded a where
- class Enum a where
- class Eq a where
- class Fractional a => Floating a where
- class Num a => Fractional a where
- class (Real a, Enum a) => Integral a where
- class Applicative m => Monad (m :: * -> *) where
- class Functor (f :: * -> *) where
- class Num a where
- class Eq a => Ord a where
- class Read a where
- class (Num a, Ord a) => Real a where
- class (RealFrac a, Floating a) => RealFloat a where
- class (Real a, Fractional a) => RealFrac a where
- class Show a where
- class Typeable (a :: k)
- class IsString a where
- class Functor f => Applicative (f :: * -> *) where
- class Foldable (t :: * -> *) where
- class (Functor t, Foldable t) => Traversable (t :: * -> *) where
- (<>) :: Semigroup a => a -> a -> a
- class Semigroup a => Monoid a where
- data Bool
- data Char
- data Double
- data Float
- data Int
- data Int32
- data Int64
- data Integer
- data Maybe a
- data Ordering
- type Rational = Ratio Integer
- data IO a
- data Word
- data Word8
- data Word32
- data Word64
- data Either a b
- class Monad m => MonadIO (m :: * -> *) where
- mfilter :: MonadPlus m => (a -> Bool) -> m a -> m a
- (<$!>) :: Monad m => (a -> b) -> m a -> m b
- unless :: Applicative f => Bool -> f () -> f ()
- replicateM_ :: Applicative m => Int -> m a -> m ()
- replicateM :: Applicative m => Int -> m a -> m [a]
- foldM_ :: (Foldable t, Monad m) => (b -> a -> m b) -> b -> t a -> m ()
- foldM :: (Foldable t, Monad m) => (b -> a -> m b) -> b -> t a -> m b
- zipWithM_ :: Applicative m => (a -> b -> m c) -> [a] -> [b] -> m ()
- zipWithM :: Applicative m => (a -> b -> m c) -> [a] -> [b] -> m [c]
- mapAndUnzipM :: Applicative m => (a -> m (b, c)) -> [a] -> m ([b], [c])
- forever :: Applicative f => f a -> f b
- (<=<) :: Monad m => (b -> m c) -> (a -> m b) -> a -> m c
- (>=>) :: Monad m => (a -> m b) -> (b -> m c) -> a -> m c
- filterM :: Applicative m => (a -> m Bool) -> [a] -> m [a]
- isSubsequenceOf :: Eq a => [a] -> [a] -> Bool
- mapAccumR :: Traversable t => (a -> b -> (a, c)) -> a -> t b -> (a, t c)
- mapAccumL :: Traversable t => (a -> b -> (a, c)) -> a -> t b -> (a, t c)
- forM :: (Traversable t, Monad m) => t a -> (a -> m b) -> m (t b)
- for :: (Traversable t, Applicative f) => t a -> (a -> f b) -> f (t b)
- first :: Arrow a => a b c -> a (b, d) (c, d)
- second :: Arrow a => a b c -> a (d, b) (d, c)
- (***) :: Arrow a => a b c -> a b' c' -> a (b, b') (c, c')
- (&&&) :: Arrow a => a b c -> a b c' -> a b (c, c')
- catchIOError :: IO a -> (IOError -> IO a) -> IO a
- annotateIOError :: IOError -> String -> Maybe Handle -> Maybe FilePath -> IOError
- modifyIOError :: (IOError -> IOError) -> IO a -> IO a
- ioeSetFileName :: IOError -> FilePath -> IOError
- ioeSetHandle :: IOError -> Handle -> IOError
- ioeSetLocation :: IOError -> String -> IOError
- ioeSetErrorString :: IOError -> String -> IOError
- ioeSetErrorType :: IOError -> IOErrorType -> IOError
- ioeGetFileName :: IOError -> Maybe FilePath
- ioeGetHandle :: IOError -> Maybe Handle
- ioeGetLocation :: IOError -> String
- ioeGetErrorString :: IOError -> String
- ioeGetErrorType :: IOError -> IOErrorType
- isUserErrorType :: IOErrorType -> Bool
- isPermissionErrorType :: IOErrorType -> Bool
- isIllegalOperationErrorType :: IOErrorType -> Bool
- isEOFErrorType :: IOErrorType -> Bool
- isFullErrorType :: IOErrorType -> Bool
- isAlreadyInUseErrorType :: IOErrorType -> Bool
- isDoesNotExistErrorType :: IOErrorType -> Bool
- isAlreadyExistsErrorType :: IOErrorType -> Bool
- userErrorType :: IOErrorType
- permissionErrorType :: IOErrorType
- illegalOperationErrorType :: IOErrorType
- eofErrorType :: IOErrorType
- fullErrorType :: IOErrorType
- alreadyInUseErrorType :: IOErrorType
- doesNotExistErrorType :: IOErrorType
- alreadyExistsErrorType :: IOErrorType
- isUserError :: IOError -> Bool
- isPermissionError :: IOError -> Bool
- isIllegalOperation :: IOError -> Bool
- isEOFError :: IOError -> Bool
- isFullError :: IOError -> Bool
- isAlreadyInUseError :: IOError -> Bool
- isDoesNotExistError :: IOError -> Bool
- isAlreadyExistsError :: IOError -> Bool
- mkIOError :: IOErrorType -> String -> Maybe Handle -> Maybe FilePath -> IOError
- tryIOError :: IO a -> IO (Either IOError a)
- ioError :: IOError -> IO a
- data IOErrorType
- type FilePath = String
- userError :: String -> IOError
- data IOException
- type IOError = IOException
- class (Typeable e, Show e) => Exception e where
- find :: Foldable t => (a -> Bool) -> t a -> Maybe a
- notElem :: (Foldable t, Eq a) => a -> t a -> Bool
- minimumBy :: Foldable t => (a -> a -> Ordering) -> t a -> a
- maximumBy :: Foldable t => (a -> a -> Ordering) -> t a -> a
- all :: Foldable t => (a -> Bool) -> t a -> Bool
- any :: Foldable t => (a -> Bool) -> t a -> Bool
- or :: Foldable t => t Bool -> Bool
- and :: Foldable t => t Bool -> Bool
- concatMap :: Foldable t => (a -> [b]) -> t a -> [b]
- msum :: (Foldable t, MonadPlus m) => t (m a) -> m a
- asum :: (Foldable t, Alternative f) => t (f a) -> f a
- sequence_ :: (Foldable t, Monad m) => t (m a) -> m ()
- sequenceA_ :: (Foldable t, Applicative f) => t (f a) -> f ()
- forM_ :: (Foldable t, Monad m) => t a -> (a -> m b) -> m ()
- mapM_ :: (Foldable t, Monad m) => (a -> m b) -> t a -> m ()
- for_ :: (Foldable t, Applicative f) => t a -> (a -> f b) -> f ()
- traverse_ :: (Foldable t, Applicative f) => (a -> f b) -> t a -> f ()
- unfoldr :: (b -> Maybe (a, b)) -> b -> [a]
- sortOn :: Ord b => (a -> b) -> [a] -> [a]
- sortBy :: (a -> a -> Ordering) -> [a] -> [a]
- sort :: Ord a => [a] -> [a]
- permutations :: [a] -> [[a]]
- subsequences :: [a] -> [[a]]
- tails :: [a] -> [[a]]
- inits :: [a] -> [[a]]
- groupBy :: (a -> a -> Bool) -> [a] -> [[a]]
- group :: Eq a => [a] -> [[a]]
- deleteFirstsBy :: (a -> a -> Bool) -> [a] -> [a] -> [a]
- unzip7 :: [(a, b, c, d, e, f, g)] -> ([a], [b], [c], [d], [e], [f], [g])
- unzip6 :: [(a, b, c, d, e, f)] -> ([a], [b], [c], [d], [e], [f])
- unzip5 :: [(a, b, c, d, e)] -> ([a], [b], [c], [d], [e])
- unzip4 :: [(a, b, c, d)] -> ([a], [b], [c], [d])
- zipWith7 :: (a -> b -> c -> d -> e -> f -> g -> h) -> [a] -> [b] -> [c] -> [d] -> [e] -> [f] -> [g] -> [h]
- zipWith6 :: (a -> b -> c -> d -> e -> f -> g) -> [a] -> [b] -> [c] -> [d] -> [e] -> [f] -> [g]
- zipWith5 :: (a -> b -> c -> d -> e -> f) -> [a] -> [b] -> [c] -> [d] -> [e] -> [f]
- zipWith4 :: (a -> b -> c -> d -> e) -> [a] -> [b] -> [c] -> [d] -> [e]
- zip7 :: [a] -> [b] -> [c] -> [d] -> [e] -> [f] -> [g] -> [(a, b, c, d, e, f, g)]
- zip6 :: [a] -> [b] -> [c] -> [d] -> [e] -> [f] -> [(a, b, c, d, e, f)]
- zip5 :: [a] -> [b] -> [c] -> [d] -> [e] -> [(a, b, c, d, e)]
- zip4 :: [a] -> [b] -> [c] -> [d] -> [(a, b, c, d)]
- genericReplicate :: Integral i => i -> a -> [a]
- genericIndex :: Integral i => [a] -> i -> a
- genericSplitAt :: Integral i => i -> [a] -> ([a], [a])
- genericDrop :: Integral i => i -> [a] -> [a]
- genericTake :: Integral i => i -> [a] -> [a]
- genericLength :: Num i => [a] -> i
- insertBy :: (a -> a -> Ordering) -> a -> [a] -> [a]
- insert :: Ord a => a -> [a] -> [a]
- partition :: (a -> Bool) -> [a] -> ([a], [a])
- transpose :: [[a]] -> [[a]]
- intersperse :: a -> [a] -> [a]
- intersectBy :: (a -> a -> Bool) -> [a] -> [a] -> [a]
- intersect :: Eq a => [a] -> [a] -> [a]
- unionBy :: (a -> a -> Bool) -> [a] -> [a] -> [a]
- union :: Eq a => [a] -> [a] -> [a]
- (\\) :: Eq a => [a] -> [a] -> [a]
- deleteBy :: (a -> a -> Bool) -> a -> [a] -> [a]
- delete :: Eq a => a -> [a] -> [a]
- nubBy :: (a -> a -> Bool) -> [a] -> [a]
- nub :: Eq a => [a] -> [a]
- isInfixOf :: Eq a => [a] -> [a] -> Bool
- isSuffixOf :: Eq a => [a] -> [a] -> Bool
- isPrefixOf :: Eq a => [a] -> [a] -> Bool
- findIndices :: (a -> Bool) -> [a] -> [Int]
- findIndex :: (a -> Bool) -> [a] -> Maybe Int
- elemIndices :: Eq a => a -> [a] -> [Int]
- elemIndex :: Eq a => a -> [a] -> Maybe Int
- stripPrefix :: Eq a => [a] -> [a] -> Maybe [a]
- dropWhileEnd :: (a -> Bool) -> [a] -> [a]
- reads :: Read a => ReadS a
- partitionEithers :: [Either a b] -> ([a], [b])
- rights :: [Either a b] -> [b]
- lefts :: [Either a b] -> [a]
- either :: (a -> c) -> (b -> c) -> Either a b -> c
- comparing :: Ord a => (b -> a) -> b -> b -> Ordering
- newtype Down a = Down a
- id :: Category cat => cat a a
- (.) :: Category cat => cat b c -> cat a b -> cat a c
- class Storable a
- lex :: ReadS String
- readParen :: Bool -> ReadS a -> ReadS a
- type ReadS a = String -> [(a, String)]
- bool :: a -> a -> Bool -> a
- on :: (b -> b -> c) -> (a -> b) -> a -> a -> c
- void :: Functor f => f a -> f ()
- (<$>) :: Functor f => (a -> b) -> f a -> f b
- lcm :: Integral a => a -> a -> a
- gcd :: Integral a => a -> a -> a
- (^^) :: (Fractional a, Integral b) => a -> b -> a
- (^) :: (Num a, Integral b) => a -> b -> a
- odd :: Integral a => a -> Bool
- even :: Integral a => a -> Bool
- showParen :: Bool -> ShowS -> ShowS
- showString :: String -> ShowS
- showChar :: Char -> ShowS
- shows :: Show a => a -> ShowS
- type ShowS = String -> String
- unzip3 :: [(a, b, c)] -> ([a], [b], [c])
- unzip :: [(a, b)] -> ([a], [b])
- zipWith3 :: (a -> b -> c -> d) -> [a] -> [b] -> [c] -> [d]
- zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
- zip3 :: [a] -> [b] -> [c] -> [(a, b, c)]
- (!!) :: [a] -> Int -> a
- lookup :: Eq a => a -> [(a, b)] -> Maybe b
- reverse :: [a] -> [a]
- break :: (a -> Bool) -> [a] -> ([a], [a])
- span :: (a -> Bool) -> [a] -> ([a], [a])
- splitAt :: Int -> [a] -> ([a], [a])
- drop :: Int -> [a] -> [a]
- take :: Int -> [a] -> [a]
- dropWhile :: (a -> Bool) -> [a] -> [a]
- takeWhile :: (a -> Bool) -> [a] -> [a]
- cycle :: [a] -> [a]
- replicate :: Int -> a -> [a]
- repeat :: a -> [a]
- iterate' :: (a -> a) -> a -> [a]
- iterate :: (a -> a) -> a -> [a]
- scanr1 :: (a -> a -> a) -> [a] -> [a]
- scanr :: (a -> b -> b) -> b -> [a] -> [b]
- scanl' :: (b -> a -> b) -> b -> [a] -> [b]
- scanl1 :: (a -> a -> a) -> [a] -> [a]
- scanl :: (b -> a -> b) -> b -> [a] -> [b]
- foldl1' :: (a -> a -> a) -> [a] -> a
- init :: [a] -> [a]
- last :: [a] -> a
- tail :: [a] -> [a]
- uncons :: [a] -> Maybe (a, [a])
- head :: [a] -> a
- mapMaybe :: (a -> Maybe b) -> [a] -> [b]
- catMaybes :: [Maybe a] -> [a]
- listToMaybe :: [a] -> Maybe a
- maybeToList :: Maybe a -> [a]
- fromMaybe :: a -> Maybe a -> a
- isNothing :: Maybe a -> Bool
- isJust :: Maybe a -> Bool
- maybe :: b -> (a -> b) -> Maybe a -> b
- swap :: (a, b) -> (b, a)
- uncurry :: (a -> b -> c) -> (a, b) -> c
- curry :: ((a, b) -> c) -> a -> b -> c
- subtract :: Num a => a -> a -> a
- asTypeOf :: a -> a -> a
- until :: (a -> Bool) -> (a -> a) -> a -> a
- ($!) :: (a -> b) -> a -> b
- flip :: (a -> b -> c) -> b -> a -> c
- const :: a -> b -> a
- ap :: Monad m => m (a -> b) -> m a -> m b
- liftM5 :: Monad m => (a1 -> a2 -> a3 -> a4 -> a5 -> r) -> m a1 -> m a2 -> m a3 -> m a4 -> m a5 -> m r
- liftM4 :: Monad m => (a1 -> a2 -> a3 -> a4 -> r) -> m a1 -> m a2 -> m a3 -> m a4 -> m r
- liftM3 :: Monad m => (a1 -> a2 -> a3 -> r) -> m a1 -> m a2 -> m a3 -> m r
- liftM2 :: Monad m => (a1 -> a2 -> r) -> m a1 -> m a2 -> m r
- liftM :: Monad m => (a1 -> r) -> m a1 -> m r
- when :: Applicative f => Bool -> f () -> f ()
- (=<<) :: Monad m => (a -> m b) -> m a -> m b
- (<|>) :: Alternative f => f a -> f a -> f a
- class (Alternative m, Monad m) => MonadPlus (m :: * -> *) where
- type String = [Char]
- undefined :: HasCallStack => a
- error :: HasCallStack => [Char] -> a
- data SomeException
- (&&) :: Bool -> Bool -> Bool
- (||) :: Bool -> Bool -> Bool
- not :: Bool -> Bool
- readLn :: (MonadIO m, Read a) => m a
- putChar :: MonadIO m => Char -> m ()
- getChar :: MonadIO m => m Char
- readMay :: Read a => Text -> Maybe a
- interact :: MonadIO m => (LText -> LText) -> m ()
- getContents :: MonadIO m => m LText
- getLine :: MonadIO m => m Text
- decodeUtf8 :: ByteString -> Text
- fpToString :: FilePath -> String
- fpFromText :: Text -> FilePath
- fpToText :: FilePath -> Text
- ltextToString :: LText -> String
- textToString :: Text -> String
- appendFile :: MonadIO m => FilePath -> Text -> m ()
- writeFile :: MonadIO m => FilePath -> Text -> m ()
- readFile :: MonadIO m => FilePath -> m Text
- readIO :: (MonadIO m, Read a) => Text -> m a
- read :: Read a => Text -> a
- fromShow :: (Show a, IsString b) => a -> b
- tshow :: Show a => a -> Text
- product :: (Foldable f, Num a) => f a -> a
- sum :: (Foldable f, Num a) => f a -> a
- intercalate :: Monoid w => w -> [w] -> w
- concat :: Monoid w => [w] -> w
- (++) :: Monoid w => w -> w -> w
- empty :: Monoid w => w
- map :: Functor f => (a -> b) -> f a -> f b
- terror :: HasCallStack => Text -> a
- print :: (MonadIO m, Show a) => a -> m ()
- putStrLn :: MonadIO m => Text -> m ()
- putStr :: MonadIO m => Text -> m ()
- getArgs :: MonadIO m => m [Text]
- equating :: Eq a => (b -> a) -> b -> b -> Bool
- type LText = Text
- type LByteString = ByteString
- type UVector = Vector
- type SVector = Vector
- data Vector a
- class (Vector Vector a, MVector MVector a) => Unbox a
- data HashMap k v
- data HashSet a
- data Text
- encodeUtf8 :: Text -> ByteString
- words :: Text -> [Text]
- lines :: Text -> [Text]
- unlines :: [Text] -> Text
- unwords :: [Text] -> Text
- class Hashable a where
- (<.>) :: FilePath -> String -> FilePath
- (</>) :: FilePath -> FilePath -> FilePath
- data Set a
- data Seq a
- data Map k a
- data IntSet
- data IntMap a
- data ByteString
- unit :: m () -> m ()
- lift :: (MonadTrans t, Monad m) => m a -> t m a
- askOracleWith :: (RuleResult q ~ a, ShakeValue q, ShakeValue a) => q -> a -> Action a
- (&*>) :: [FilePattern] -> ([FilePath] -> Action ()) -> Rules ()
- (|*>) :: [FilePattern] -> (FilePath -> Action ()) -> Rules ()
- (*>) :: FilePattern -> (FilePath -> Action ()) -> Rules ()
- (*>>) :: [FilePattern] -> ([FilePath] -> Action ()) -> Rules ()
- (?>>) :: (FilePath -> Maybe [FilePath]) -> ([FilePath] -> Action ()) -> Rules ()
- (**>) :: [FilePattern] -> (FilePath -> Action ()) -> Rules ()
- shakeOptDescrs :: [OptDescr (Either String (ShakeOptions -> ShakeOptions))]
- shakeArgsOptionsWith :: ShakeOptions -> [OptDescr (Either String a)] -> (ShakeOptions -> [a] -> [String] -> IO (Maybe (ShakeOptions, Rules ()))) -> IO ()
- shakeArgsWith :: ShakeOptions -> [OptDescr (Either String a)] -> ([a] -> [String] -> IO (Maybe (Rules ()))) -> IO ()
- shakeArgs :: ShakeOptions -> Rules () -> IO ()
- cmd_ :: (CmdArguments args, Unit args) => args :-> Action ()
- cmd :: CmdArguments args => args :-> Action r
- command_ :: [CmdOption] -> String -> [String] -> Action ()
- command :: CmdResult r => [CmdOption] -> String -> [String] -> Action r
- addEnv :: MonadIO m => [(String, String)] -> m CmdOption
- addPath :: MonadIO m => [String] -> [String] -> m CmdOption
- newtype Stdout a = Stdout {
- fromStdout :: a
- newtype Stderr a = Stderr {
- fromStderr :: a
- newtype Stdouterr a = Stdouterr {
- fromStdouterr :: a
- newtype Exit = Exit {}
- newtype Process = Process {}
- newtype CmdTime = CmdTime {}
- newtype CmdLine = CmdLine {}
- class CmdString a
- class CmdResult a
- newCache :: (Eq k, Hashable k) => (k -> Action v) -> Rules (k -> Action v)
- withResources :: [(Resource, Int)] -> Action a -> Action a
- newThrottle :: String -> Int -> Double -> Rules Resource
- newResource :: String -> Int -> Rules Resource
- par :: Action a -> Action b -> Action (a, b)
- forP :: [a] -> (a -> Action b) -> Action [b]
- withTempDirWithin :: FilePath -> (FilePath -> Action a) -> Action a
- withTempDir :: (FilePath -> Action a) -> Action a
- withTempFileWithin :: FilePath -> (FilePath -> Action a) -> Action a
- withTempFile :: (FilePath -> Action a) -> Action a
- writeFileChanged :: MonadIO m => FilePath -> String -> m ()
- writeFileLines :: MonadIO m => FilePath -> [String] -> m ()
- readFileLines :: FilePath -> Action [String]
- writeFile' :: MonadIO m => FilePath -> String -> m ()
- readFile' :: FilePath -> Action String
- copyFileChanged :: FilePath -> FilePath -> Action ()
- copyFile' :: FilePath -> FilePath -> Action ()
- addShakeExtra :: Typeable a => a -> HashMap TypeRep Dynamic -> HashMap TypeRep Dynamic
- getShakeExtraRules :: Typeable a => Rules (Maybe a)
- getShakeExtra :: Typeable a => Action (Maybe a)
- getHashedShakeVersion :: [FilePath] -> IO String
- shake :: ShakeOptions -> Rules () -> IO ()
- removeFilesAfter :: FilePath -> [FilePattern] -> Action ()
- removeFiles :: FilePath -> [FilePattern] -> IO ()
- getDirectoryFilesIO :: FilePath -> [FilePattern] -> IO [FilePath]
- getDirectoryDirs :: FilePath -> Action [FilePath]
- getDirectoryFiles :: FilePath -> [FilePattern] -> Action [FilePath]
- getDirectoryContents :: FilePath -> Action [FilePath]
- getEnvWithDefault :: String -> String -> Action String
- getEnv :: String -> Action (Maybe String)
- doesDirectoryExist :: FilePath -> Action Bool
- doesFileExist :: FilePath -> Action Bool
- (&?>) :: (FilePath -> Maybe [FilePath]) -> ([FilePath] -> Action ()) -> Rules ()
- (&%>) :: [FilePattern] -> ([FilePath] -> Action ()) -> Rules ()
- orderOnly :: [FilePath] -> Action ()
- (%>) :: FilePattern -> (FilePath -> Action ()) -> Rules ()
- (|%>) :: [FilePattern] -> (FilePath -> Action ()) -> Rules ()
- (?>) :: (FilePath -> Bool) -> (FilePath -> Action ()) -> Rules ()
- (~>) :: String -> Action () -> Rules ()
- phonys :: (String -> Maybe (Action ())) -> Rules ()
- phony :: String -> Action () -> Rules ()
- want :: [FilePath] -> Rules ()
- trackAllow :: [FilePattern] -> Action ()
- trackWrite :: [FilePath] -> Action ()
- trackRead :: [FilePath] -> Action ()
- needed :: [FilePath] -> Action ()
- needHasChanged :: [FilePath] -> Action [FilePath]
- need :: [FilePath] -> Action ()
- resultHasChanged :: FilePath -> Action Bool
- askOracle :: (RuleResult q ~ a, ShakeValue q, ShakeValue a) => q -> Action a
- addOracleCache :: (RuleResult q ~ a, ShakeValue q, ShakeValue a) => (q -> Action a) -> Rules (q -> Action a)
- addOracle :: (RuleResult q ~ a, ShakeValue q, ShakeValue a) => (q -> Action a) -> Rules (q -> Action a)
- alwaysRerun :: Action ()
- batch :: Int -> ((a -> Action ()) -> Rules ()) -> (a -> Action b) -> ([b] -> Action ()) -> Rules ()
- orderOnlyAction :: Action a -> Action a
- parallel :: [Action a] -> Action [a]
- unsafeExtraThread :: Action a -> Action a
- newCacheIO :: (Eq k, Hashable k) => (k -> Action v) -> IO (k -> Action v)
- withResource :: Resource -> Int -> Action a -> Action a
- traced :: String -> IO a -> Action a
- quietly :: Action a -> Action a
- withVerbosity :: Verbosity -> Action a -> Action a
- getVerbosity :: Action Verbosity
- putQuiet :: String -> Action ()
- putNormal :: String -> Action ()
- putLoud :: String -> Action ()
- runAfter :: IO () -> Action ()
- getProgress :: Action Progress
- getShakeOptions :: Action ShakeOptions
- actionFinally :: Action a -> IO b -> Action a
- actionOnException :: Action a -> IO b -> Action a
- withoutActions :: Rules () -> Rules ()
- action :: Action a -> Rules ()
- alternatives :: Rules () -> Rules ()
- priority :: Double -> Rules () -> Rules ()
- getShakeOptionsRules :: Rules ShakeOptions
- data Rules a
- type family RuleResult key :: *
- data Action a
- shakeOptions :: ShakeOptions
- data Rebuild
- data Lint
- data Change
- data ShakeOptions = ShakeOptions {
- shakeFiles :: FilePath
- shakeThreads :: Int
- shakeVersion :: String
- shakeVerbosity :: Verbosity
- shakeStaunch :: Bool
- shakeReport :: [FilePath]
- shakeLint :: Maybe Lint
- shakeLintInside :: [FilePath]
- shakeLintIgnore :: [FilePattern]
- shakeCommandOptions :: [CmdOption]
- shakeFlush :: Maybe Double
- shakeRebuild :: [(Rebuild, FilePattern)]
- shakeAbbreviations :: [(String, String)]
- shakeStorageLog :: Bool
- shakeLineBuffering :: Bool
- shakeTimings :: Bool
- shakeRunCommands :: Bool
- shakeChange :: Change
- shakeCreationCheck :: Bool
- shakeLiveFiles :: [FilePath]
- shakeVersionIgnore :: Bool
- shakeColor :: Bool
- shakeProgress :: IO Progress -> IO ()
- shakeOutput :: Verbosity -> String -> IO ()
- shakeExtra :: HashMap TypeRep Dynamic
- data Verbosity
- progressSimple :: IO Progress -> IO ()
- progressProgram :: IO (String -> IO ())
- progressTitlebar :: String -> IO ()
- progressDisplay :: Double -> (String -> IO ()) -> IO Progress -> IO ()
- data Progress = Progress {
- isFailure :: !(Maybe String)
- countSkipped :: !Int
- countBuilt :: !Int
- countUnknown :: !Int
- countTodo :: !Int
- timeSkipped :: !Double
- timeBuilt :: !Double
- timeUnknown :: !Double
- timeTodo :: !(Double, Int)
- newThrottleIO :: String -> Int -> Double -> IO Resource
- newResourceIO :: String -> Int -> IO Resource
- data Resource
- type ShakeValue a = (Show a, Typeable a, Eq a, Hashable a, Binary a, NFData a)
- filePattern :: FilePattern -> FilePath -> Maybe [String]
- (?==) :: FilePattern -> FilePath -> Bool
- (<//>) :: FilePattern -> FilePattern -> FilePattern
- type FilePattern = String
- data ShakeException = ShakeException {}
- data CmdOption
- = Cwd FilePath
- | Env [(String, String)]
- | AddEnv String String
- | RemEnv String
- | AddPath [String] [String]
- | Stdin String
- | StdinBS ByteString
- | FileStdin FilePath
- | Shell
- | BinaryPipes
- | Traced String
- | Timeout Double
- | WithStdout Bool
- | WithStderr Bool
- | EchoStdout Bool
- | EchoStderr Bool
- | FileStdout FilePath
- | FileStderr FilePath
- | AutoDeps
- (<:>) :: (IsString m, Monoid m) => m -> m -> m
- (<->) :: (IsString m, Monoid m) => m -> m -> m
- (<=>) :: (IsString m, Monoid m) => m -> m -> m
- timestamp :: Action String
- buildFile :: FilePath -> FilePath
- fakeFile :: FilePath -> FilePath
- metaFile :: FilePath -> FilePath
- mirrorDir :: Action FilePath
- parentDir :: Action FilePath
- getVar :: String -> Action String
- getFlag :: String -> Action Bool
- cmdArgs :: String -> [String] -> Action String
- cmdArgs_ :: String -> [String] -> Action ()
- cmdArgsDir :: FilePath -> String -> [String] -> Action String
- cmdArgsDir_ :: FilePath -> String -> [String] -> Action ()
- stack :: FilePath -> [String] -> Action String
- stack_ :: FilePath -> [String] -> Action ()
- stackExec :: FilePath -> String -> [String] -> Action String
- stackExec_ :: FilePath -> String -> [String] -> Action ()
- sed_ :: FilePath -> [String] -> Action ()
- replace :: FilePath -> FilePath -> String -> String -> Action ()
- git :: FilePath -> [String] -> Action String
- git_ :: FilePath -> [String] -> Action ()
- schemaApply_ :: FilePath -> [String] -> Action ()
- m4 :: [String] -> Action String
- aws :: [String] -> Action String
- rsync_ :: [String] -> Action ()
- ssh :: String -> [String] -> Action String
- ssh_ :: String -> [String] -> Action ()
- sshDir :: FilePath -> String -> [String] -> Action String
- sshDir_ :: FilePath -> String -> [String] -> Action ()
- rssh :: [String] -> Action String
- rssh_ :: [String] -> Action ()
- rdocker_ :: [String] -> Action ()
- docker_ :: [String] -> Action ()
- xdocker_ :: [String] -> Action ()
- convox_ :: [String] -> Action ()
- fake :: FilePath -> [FilePattern] -> String -> ([FilePath] -> Action ()) -> Rules ()
- meta :: FilePath -> Action String -> Rules ()
- preprocess :: FilePattern -> FilePath -> Action [(String, String)] -> Rules ()
- getHashedVersion :: FilePath -> [FilePattern] -> Action String
- hsRules :: FilePath -> [FilePattern] -> Rules ()
- stackRules :: FilePath -> [FilePattern] -> Rules ()
- stackTargetRules :: FilePath -> String -> [FilePattern] -> Rules ()
- cabalRules :: FilePath -> FilePath -> Rules ()
- dbRules :: FilePath -> Rules ()
- dockerRules :: FilePath -> [FilePattern] -> Rules ()
- shakeMain :: Rules () -> IO ()
Documentation
The value of seq a b is bottom if a is bottom, and
otherwise equal to b. In other words, it evaluates the first
argument a to weak head normal form (WHNF). seq is usually
introduced to improve performance by avoiding unneeded laziness.
A note on evaluation order: the expression seq a b does
not guarantee that a will be evaluated before b.
The only guarantee given by seq is that the both a
and b will be evaluated before seq returns a value.
In particular, this means that b may be evaluated before
a. If you need to guarantee a specific order of evaluation,
you must use the function pseq from the "parallel" package.
filter :: (a -> Bool) -> [a] -> [a] #
filter, applied to a predicate and a list, returns the list of
those elements that satisfy the predicate; i.e.,
filter p xs = [ x | x <- xs, p x]
($) :: (a -> b) -> a -> b infixr 0 #
Application operator. This operator is redundant, since ordinary
application (f x) means the same as (f . However, $ x)$ has
low, right-associative binding precedence, so it sometimes allows
parentheses to be omitted; for example:
f $ g $ h x = f (g (h x))
It is also useful in higher-order situations, such as map ($ 0) xszipWith ($) fs xs
fromIntegral :: (Integral a, Num b) => a -> b #
general coercion from integral types
realToFrac :: (Real a, Fractional b) => a -> b #
general coercion to fractional types
guard :: Alternative f => Bool -> f () #
Conditional failure of Alternative computations. Defined by
guard True =pure() guard False =empty
Examples
Common uses of guard include conditionally signaling an error in
an error monad and conditionally rejecting the current choice in an
Alternative-based parser.
As an example of signaling an error in the error monad Maybe,
consider a safe division function safeDiv x y that returns
Nothing when the denominator y is zero and Just (x `div`
y)
>>> safeDiv 4 0 Nothing >>> safeDiv 4 2 Just 2
A definition of safeDiv using guards, but not guard:
safeDiv :: Int -> Int -> Maybe Int
safeDiv x y | y /= 0 = Just (x `div` y)
| otherwise = Nothing
A definition of safeDiv using guard and Monad do-notation:
safeDiv :: Int -> Int -> Maybe Int safeDiv x y = do guard (y /= 0) return (x `div` y)
join :: Monad m => m (m a) -> m a #
The join function is the conventional monad join operator. It
is used to remove one level of monadic structure, projecting its
bound argument into the outer level.
The Bounded class is used to name the upper and lower limits of a
type. Ord is not a superclass of Bounded since types that are not
totally ordered may also have upper and lower bounds.
The Bounded class may be derived for any enumeration type;
minBound is the first constructor listed in the data declaration
and maxBound is the last.
Bounded may also be derived for single-constructor datatypes whose
constituent types are in Bounded.
Instances
Class Enum defines operations on sequentially ordered types.
The enumFrom... methods are used in Haskell's translation of
arithmetic sequences.
Instances of Enum may be derived for any enumeration type (types
whose constructors have no fields). The nullary constructors are
assumed to be numbered left-to-right by fromEnum from 0 through n-1.
See Chapter 10 of the Haskell Report for more details.
For any type that is an instance of class Bounded as well as Enum,
the following should hold:
- The calls
succmaxBoundpredminBound fromEnumandtoEnumshould give a runtime error if the result value is not representable in the result type. For example,toEnum7 ::BoolenumFromandenumFromThenshould be defined with an implicit bound, thus:
enumFrom x = enumFromTo x maxBound
enumFromThen x y = enumFromThenTo x y bound
where
bound | fromEnum y >= fromEnum x = maxBound
| otherwise = minBoundMethods
the successor of a value. For numeric types, succ adds 1.
the predecessor of a value. For numeric types, pred subtracts 1.
Convert from an Int.
Convert to an Int.
It is implementation-dependent what fromEnum returns when
applied to a value that is too large to fit in an Int.
Used in Haskell's translation of [n..].
enumFromThen :: a -> a -> [a] #
Used in Haskell's translation of [n,n'..].
enumFromTo :: a -> a -> [a] #
Used in Haskell's translation of [n..m].
enumFromThenTo :: a -> a -> a -> [a] #
Used in Haskell's translation of [n,n'..m].
Instances
The Eq class defines equality (==) and inequality (/=).
All the basic datatypes exported by the Prelude are instances of Eq,
and Eq may be derived for any datatype whose constituents are also
instances of Eq.
Instances
| Eq Bool | |
| Eq Char | |
| Eq Double | |
| Eq Float | |
| Eq Int | |
| Eq Int8 | Since: base-2.1 |
| Eq Int16 | Since: base-2.1 |
| Eq Int32 | Since: base-2.1 |
| Eq Int64 | Since: base-2.1 |
| Eq Integer | |
| Eq Ordering | |
| Eq Word | |
| Eq Word8 | Since: base-2.1 |
| Eq Word16 | Since: base-2.1 |
| Eq Word32 | Since: base-2.1 |
| Eq Word64 | Since: base-2.1 |
| Eq SomeTypeRep | |
Defined in Data.Typeable.Internal | |
| Eq () | |
| Eq TyCon | |
| Eq Module | |
| Eq TrName | |
| Eq Handle | Since: base-4.1.0.0 |
| Eq BigNat | |
| Eq Void | Since: base-4.8.0.0 |
| Eq SpecConstrAnnotation | |
Defined in GHC.Exts Methods (==) :: SpecConstrAnnotation -> SpecConstrAnnotation -> Bool # (/=) :: SpecConstrAnnotation -> SpecConstrAnnotation -> Bool # | |
| Eq AsyncException | |
Defined in GHC.IO.Exception Methods (==) :: AsyncException -> AsyncException -> Bool # (/=) :: AsyncException -> AsyncException -> Bool # | |
| Eq ArrayException | |
Defined in GHC.IO.Exception Methods (==) :: ArrayException -> ArrayException -> Bool # (/=) :: ArrayException -> ArrayException -> Bool # | |
| Eq ExitCode | |
| Eq IOErrorType | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
| Eq BufferMode | |
Defined in GHC.IO.Handle.Types | |
| Eq Newline | |
| Eq NewlineMode | |
Defined in GHC.IO.Handle.Types | |
| Eq MaskingState | |
Defined in GHC.IO | |
| Eq IOException | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
| Eq ErrorCall | |
| Eq ArithException | |
Defined in GHC.Exception Methods (==) :: ArithException -> ArithException -> Bool # (/=) :: ArithException -> ArithException -> Bool # | |
| Eq Fixity | |
| Eq Associativity | |
Defined in GHC.Generics Methods (==) :: Associativity -> Associativity -> Bool # (/=) :: Associativity -> Associativity -> Bool # | |
| Eq SourceUnpackedness | |
Defined in GHC.Generics Methods (==) :: SourceUnpackedness -> SourceUnpackedness -> Bool # (/=) :: SourceUnpackedness -> SourceUnpackedness -> Bool # | |
| Eq SourceStrictness | |
Defined in GHC.Generics Methods (==) :: SourceStrictness -> SourceStrictness -> Bool # (/=) :: SourceStrictness -> SourceStrictness -> Bool # | |
| Eq DecidedStrictness | |
Defined in GHC.Generics Methods (==) :: DecidedStrictness -> DecidedStrictness -> Bool # (/=) :: DecidedStrictness -> DecidedStrictness -> Bool # | |
| Eq CChar | |
| Eq CSChar | |
| Eq CUChar | |
| Eq CShort | |
| Eq CUShort | |
| Eq CInt | |
| Eq CUInt | |
| Eq CLong | |
| Eq CULong | |
| Eq CLLong | |
| Eq CULLong | |
| Eq CBool | |
| Eq CFloat | |
| Eq CDouble | |
| Eq CPtrdiff | |
| Eq CSize | |
| Eq CWchar | |
| Eq CSigAtomic | |
Defined in Foreign.C.Types | |
| Eq CClock | |
| Eq CTime | |
| Eq CUSeconds | |
| Eq CSUSeconds | |
Defined in Foreign.C.Types | |
| Eq CIntPtr | |
| Eq CUIntPtr | |
| Eq CIntMax | |
| Eq CUIntMax | |
| Eq GeneralCategory | |
Defined in GHC.Unicode Methods (==) :: GeneralCategory -> GeneralCategory -> Bool # (/=) :: GeneralCategory -> GeneralCategory -> Bool # | |
| Eq SrcLoc | |
| Eq IntSet | |
| Eq ByteString | |
Defined in Data.ByteString.Internal | |
| Eq Clock | |
| Eq TimeSpec | |
| Eq XdgDirectory | |
Defined in System.Directory | |
| Eq FileType | |
| Eq Permissions | |
Defined in System.Directory.Internal.Common | |
| Eq StdStream | |
| Eq CmdSpec | |
| Eq CreateProcess | |
Defined in System.Process.Common Methods (==) :: CreateProcess -> CreateProcess -> Bool # (/=) :: CreateProcess -> CreateProcess -> Bool # | |
| Eq ByteArray | Since: primitive-0.6.3.0 |
| Eq Addr | |
| Eq FileQ | |
| Eq EqualCost | |
| Eq Key | |
| Eq QTypeRep | |
| Eq CmdArgument | |
Defined in Development.Shake.Command | |
| Eq RunChanged | |
Defined in Development.Shake.Internal.Core.Types | |
| Eq Rebuild | |
| Eq Lint | |
| Eq Change | |
| Eq Verbosity | |
| Eq Progress | |
| Eq Resource | |
| Eq CmdOption | |
| Eq LocalTime | |
| Eq DoesDirectoryExistQ | |
| Eq DoesFileExistQ | |
| Eq DoesDirectoryExistA | |
| Eq DoesFileExistA | |
| Eq GetDirectoryA | |
| Eq GetDirectoryContentsQ | |
| Eq GetDirectoryDirsQ | |
| Eq GetDirectoryFilesQ | |
| Eq GetEnvA | |
| Eq GetEnvQ | |
| Eq FilesQ | |
| Eq AlwaysRerunQ | |
| Eq Pat | |
| Eq PID | |
| Eq Result | |
| Eq Str | |
| Eq Extra | |
| Eq CodePoint | |
| Eq DecoderState | |
| Eq a => Eq [a] | |
| Eq a => Eq (Maybe a) | |
| Eq a => Eq (Ratio a) | |
| Eq p => Eq (Par1 p) | |
| Eq a => Eq (Complex a) | |
| Eq a => Eq (Min a) | |
| Eq a => Eq (Max a) | |
| Eq a => Eq (First a) | |
| Eq a => Eq (Last a) | |
| Eq m => Eq (WrappedMonoid m) | |
Defined in Data.Semigroup Methods (==) :: WrappedMonoid m -> WrappedMonoid m -> Bool # (/=) :: WrappedMonoid m -> WrappedMonoid m -> Bool # | |
| Eq a => Eq (Option a) | |
| Eq a => Eq (Identity a) | |
| Eq a => Eq (Down a) | |
| Eq a => Eq (NonEmpty a) | |
| Eq a => Eq (Vector a) | |
| Eq a => Eq (HashSet a) | |
| Eq a => Eq (Set a) | |
| Eq a => Eq (Seq a) | |
| Eq a => Eq (IntMap a) | |
| Eq a => Eq (Tree a) | |
| Eq a => Eq (ViewL a) | |
| Eq a => Eq (ViewR a) | |
| Eq a => Eq (Hashed a) | Uses precomputed hash to detect inequality faster |
| (Eq a, PrimUnlifted a) => Eq (UnliftedArray a) | |
Defined in Data.Primitive.UnliftedArray Methods (==) :: UnliftedArray a -> UnliftedArray a -> Bool # (/=) :: UnliftedArray a -> UnliftedArray a -> Bool # | |
| (Eq a, Prim a) => Eq (PrimArray a) | Since: primitive-0.6.4.0 |
| Eq a => Eq (SmallArray a) | |
Defined in Data.Primitive.SmallArray | |
| Eq a => Eq (Array a) | |
| Eq a => Eq (UserRule a) | |
| (Storable a, Eq a) => Eq (Vector a) | |
| (Prim a, Eq a) => Eq (Vector a) | |
| Eq answer => Eq (OracleA answer) | |
| Eq question => Eq (OracleQ question) | |
| (Eq a, Eq b) => Eq (Either a b) | |
| Eq (V1 p) | Since: base-4.9.0.0 |
| Eq (U1 p) | Since: base-4.9.0.0 |
| Eq (TypeRep a) | Since: base-2.1 |
| (Eq a, Eq b) => Eq (a, b) | |
| Eq a => Eq (Arg a b) | Since: base-4.9.0.0 |
| (Eq k, Eq v) => Eq (HashMap k v) | |
| (Eq k, Eq a) => Eq (Map k a) | |
| Eq (MutableUnliftedArray s a) | |
Defined in Data.Primitive.UnliftedArray Methods (==) :: MutableUnliftedArray s a -> MutableUnliftedArray s a -> Bool # (/=) :: MutableUnliftedArray s a -> MutableUnliftedArray s a -> Bool # | |
| Eq (SmallMutableArray s a) | |
Defined in Data.Primitive.SmallArray Methods (==) :: SmallMutableArray s a -> SmallMutableArray s a -> Bool # (/=) :: SmallMutableArray s a -> SmallMutableArray s a -> Bool # | |
| Eq (MutableArray s a) | |
Defined in Data.Primitive.Array Methods (==) :: MutableArray s a -> MutableArray s a -> Bool # (/=) :: MutableArray s a -> MutableArray s a -> Bool # | |
| (Eq k, Eq v) => Eq (Leaf k v) | |
| Eq (f p) => Eq (Rec1 f p) | |
| Eq (URec (Ptr ()) p) | |
| Eq (URec Char p) | |
| Eq (URec Double p) | |
| Eq (URec Float p) | |
| Eq (URec Int p) | |
| Eq (URec Word p) | |
| (Eq a, Eq b, Eq c) => Eq (a, b, c) | |
| Eq a => Eq (Const a b) | |
| Eq (a :~: b) | |
| (Eq e, Eq1 m, Eq a) => Eq (ErrorT e m a) | |
| Eq c => Eq (K1 i c p) | |
| (Eq (f p), Eq (g p)) => Eq ((f :+: g) p) | |
| (Eq (f p), Eq (g p)) => Eq ((f :*: g) p) | |
| (Eq a, Eq b, Eq c, Eq d) => Eq (a, b, c, d) | |
| (Eq1 f, Eq1 g, Eq a) => Eq (Product f g a) | Since: base-4.9.0.0 |
| (Eq1 f, Eq1 g, Eq a) => Eq (Sum f g a) | Since: base-4.9.0.0 |
| Eq (a :~~: b) | Since: base-4.10.0.0 |
| Eq (f p) => Eq (M1 i c f p) | |
| Eq (f (g p)) => Eq ((f :.: g) p) | |
| (Eq a, Eq b, Eq c, Eq d, Eq e) => Eq (a, b, c, d, e) | |
| (Eq1 f, Eq1 g, Eq a) => Eq (Compose f g a) | Since: base-4.9.0.0 |
| (Eq a, Eq b, Eq c, Eq d, Eq e, Eq f) => Eq (a, b, c, d, e, f) | |
| (Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g) => Eq (a, b, c, d, e, f, g) | |
| (Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h) => Eq (a, b, c, d, e, f, g, h) | |
| (Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i) => Eq (a, b, c, d, e, f, g, h, i) | |
| (Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j) => Eq (a, b, c, d, e, f, g, h, i, j) | |
| (Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k) => Eq (a, b, c, d, e, f, g, h, i, j, k) | |
| (Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k, Eq l) => Eq (a, b, c, d, e, f, g, h, i, j, k, l) | |
| (Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k, Eq l, Eq m) => Eq (a, b, c, d, e, f, g, h, i, j, k, l, m) | |
| (Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k, Eq l, Eq m, Eq n) => Eq (a, b, c, d, e, f, g, h, i, j, k, l, m, n) | |
| (Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k, Eq l, Eq m, Eq n, Eq o) => Eq (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) | |
class Fractional a => Floating a where #
Trigonometric and hyperbolic functions and related functions.
Minimal complete definition
pi, exp, log, sin, cos, asin, acos, atan, sinh, cosh, asinh, acosh, atanh
Instances
class Num a => Fractional a where #
Fractional numbers, supporting real division.
Minimal complete definition
fromRational, (recip | (/))
Methods
fractional division
reciprocal fraction
fromRational :: Rational -> a #
Conversion from a Rational (that is Ratio IntegerfromRational
to a value of type Rational, so such literals have type
(.Fractional a) => a
Instances
| Fractional CFloat | |
| Fractional CDouble | |
| Integral a => Fractional (Ratio a) | Since: base-2.0.1 |
| RealFloat a => Fractional (Complex a) | Since: base-2.1 |
| Fractional a => Fractional (Identity a) | |
| Fractional a => Fractional (Const a b) | |
class (Real a, Enum a) => Integral a where #
Integral numbers, supporting integer division.
Methods
quot :: a -> a -> a infixl 7 #
integer division truncated toward zero
integer remainder, satisfying
(x `quot` y)*y + (x `rem` y) == x
integer division truncated toward negative infinity
integer modulus, satisfying
(x `div` y)*y + (x `mod` y) == x
conversion to Integer
Instances
class Applicative m => Monad (m :: * -> *) where #
The Monad class defines the basic operations over a monad,
a concept from a branch of mathematics known as category theory.
From the perspective of a Haskell programmer, however, it is best to
think of a monad as an abstract datatype of actions.
Haskell's do expressions provide a convenient syntax for writing
monadic expressions.
Instances of Monad should satisfy the following laws:
Furthermore, the Monad and Applicative operations should relate as follows:
The above laws imply:
and that pure and (<*>) satisfy the applicative functor laws.
The instances of Monad for lists, Maybe and IO
defined in the Prelude satisfy these laws.
Minimal complete definition
Methods
(>>=) :: m a -> (a -> m b) -> m b infixl 1 #
Sequentially compose two actions, passing any value produced by the first as an argument to the second.
(>>) :: m a -> m b -> m b infixl 1 #
Sequentially compose two actions, discarding any value produced by the first, like sequencing operators (such as the semicolon) in imperative languages.
Inject a value into the monadic type.
Fail with a message. This operation is not part of the
mathematical definition of a monad, but is invoked on pattern-match
failure in a do expression.
As part of the MonadFail proposal (MFP), this function is moved
to its own class MonadFail (see Control.Monad.Fail for more
details). The definition here will be removed in a future
release.
Instances
| Monad [] | Since: base-2.1 |
| Monad Maybe | Since: base-2.1 |
| Monad IO | Since: base-2.1 |
| Monad Par1 | Since: base-4.9.0.0 |
| Monad Complex | Since: base-4.9.0.0 |
| Monad Min | Since: base-4.9.0.0 |
| Monad Max | Since: base-4.9.0.0 |
| Monad First | Since: base-4.9.0.0 |
| Monad Last | Since: base-4.9.0.0 |
| Monad Option | Since: base-4.9.0.0 |
| Monad Identity | Since: base-4.8.0.0 |
| Monad Down | Since: base-4.11.0.0 |
| Monad ReadP | Since: base-2.1 |
| Monad NonEmpty | Since: base-4.9.0.0 |
| Monad Vector | |
| Monad Seq | |
| Monad Put | |
| Monad Tree | |
| Monad SmallArray | |
Defined in Data.Primitive.SmallArray Methods (>>=) :: SmallArray a -> (a -> SmallArray b) -> SmallArray b # (>>) :: SmallArray a -> SmallArray b -> SmallArray b # return :: a -> SmallArray a # fail :: String -> SmallArray a # | |
| Monad Array | |
| Monad Rules | |
| Monad Action | |
| Monad P | Since: base-2.1 |
| Monad (Either e) | Since: base-4.4.0.0 |
| Monad (U1 :: * -> *) | Since: base-4.9.0.0 |
| Monoid a => Monad ((,) a) | Since: base-4.9.0.0 |
| ArrowApply a => Monad (ArrowMonad a) | Since: base-2.1 |
Defined in Control.Arrow Methods (>>=) :: ArrowMonad a a0 -> (a0 -> ArrowMonad a b) -> ArrowMonad a b # (>>) :: ArrowMonad a a0 -> ArrowMonad a b -> ArrowMonad a b # return :: a0 -> ArrowMonad a a0 # fail :: String -> ArrowMonad a a0 # | |
| Monad f => Monad (Rec1 f) | Since: base-4.9.0.0 |
| (Applicative f, Monad f) => Monad (WhenMissing f x) | Equivalent to Since: containers-0.5.9 |
Defined in Data.IntMap.Internal Methods (>>=) :: WhenMissing f x a -> (a -> WhenMissing f x b) -> WhenMissing f x b # (>>) :: WhenMissing f x a -> WhenMissing f x b -> WhenMissing f x b # return :: a -> WhenMissing f x a # fail :: String -> WhenMissing f x a # | |
| (Monad m, Error e) => Monad (ErrorT e m) | |
| Monad (RAW ro rw) | |
| Monad ((->) r :: * -> *) | Since: base-2.1 |
| (Monad f, Monad g) => Monad (f :*: g) | Since: base-4.9.0.0 |
| (Monad f, Monad g) => Monad (Product f g) | Since: base-4.9.0.0 |
| (Monad f, Applicative f) => Monad (WhenMatched f x y) | Equivalent to Since: containers-0.5.9 |
Defined in Data.IntMap.Internal Methods (>>=) :: WhenMatched f x y a -> (a -> WhenMatched f x y b) -> WhenMatched f x y b # (>>) :: WhenMatched f x y a -> WhenMatched f x y b -> WhenMatched f x y b # return :: a -> WhenMatched f x y a # fail :: String -> WhenMatched f x y a # | |
| (Applicative f, Monad f) => Monad (WhenMissing f k x) | Equivalent to Since: containers-0.5.9 |
Defined in Data.Map.Internal Methods (>>=) :: WhenMissing f k x a -> (a -> WhenMissing f k x b) -> WhenMissing f k x b # (>>) :: WhenMissing f k x a -> WhenMissing f k x b -> WhenMissing f k x b # return :: a -> WhenMissing f k x a # fail :: String -> WhenMissing f k x a # | |
| Monad f => Monad (M1 i c f) | Since: base-4.9.0.0 |
| (Monad f, Applicative f) => Monad (WhenMatched f k x y) | Equivalent to Since: containers-0.5.9 |
Defined in Data.Map.Internal Methods (>>=) :: WhenMatched f k x y a -> (a -> WhenMatched f k x y b) -> WhenMatched f k x y b # (>>) :: WhenMatched f k x y a -> WhenMatched f k x y b -> WhenMatched f k x y b # return :: a -> WhenMatched f k x y a # fail :: String -> WhenMatched f k x y a # | |
class Functor (f :: * -> *) where #
The Functor class is used for types that can be mapped over.
Instances of Functor should satisfy the following laws:
fmap id == id fmap (f . g) == fmap f . fmap g
The instances of Functor for lists, Maybe and IO
satisfy these laws.
Minimal complete definition
Instances
| Functor [] | Since: base-2.1 |
| Functor Maybe | Since: base-2.1 |
| Functor IO | Since: base-2.1 |
| Functor Par1 | |
| Functor Complex | |
| Functor Min | Since: base-4.9.0.0 |
| Functor Max | Since: base-4.9.0.0 |
| Functor First | Since: base-4.9.0.0 |
| Functor Last | Since: base-4.9.0.0 |
| Functor Option | Since: base-4.9.0.0 |
| Functor ArgOrder | Since: base-4.6.0.0 |
| Functor OptDescr | Since: base-4.6.0.0 |
| Functor ArgDescr | Since: base-4.6.0.0 |
| Functor Identity | Since: base-4.8.0.0 |
| Functor Down | Since: base-4.11.0.0 |
| Functor ReadP | Since: base-2.1 |
| Functor NonEmpty | Since: base-4.9.0.0 |
| Functor Vector | |
| Functor Seq | |
| Functor IntMap | |
| Functor Put | |
Defined in Data.ByteString.Builder.Internal | |
| Functor Tree | |
| Functor FingerTree | |
Defined in Data.Sequence.Internal Methods fmap :: (a -> b) -> FingerTree a -> FingerTree b # (<$) :: a -> FingerTree b -> FingerTree a # | |
| Functor Digit | |
| Functor Node | |
| Functor Elem | |
| Functor ViewL | |
| Functor ViewR | |
| Functor SmallArray | |
Defined in Data.Primitive.SmallArray Methods fmap :: (a -> b) -> SmallArray a -> SmallArray b # (<$) :: a -> SmallArray b -> SmallArray a # | |
| Functor Array | |
| Functor Rules | |
| Functor Action | |
| Functor RunResult | |
| Functor UserRule | |
| Functor P | |
Defined in Text.ParserCombinators.ReadP | |
| Functor (Either a) | Since: base-3.0 |
| Functor (V1 :: * -> *) | Since: base-4.9.0.0 |
| Functor (U1 :: * -> *) | Since: base-4.9.0.0 |
| Functor ((,) a) | Since: base-2.1 |
| Functor (Arg a) | Since: base-4.9.0.0 |
| Arrow a => Functor (ArrowMonad a) | Since: base-4.6.0.0 |
Defined in Control.Arrow Methods fmap :: (a0 -> b) -> ArrowMonad a a0 -> ArrowMonad a b # (<$) :: a0 -> ArrowMonad a b -> ArrowMonad a a0 # | |
| Functor (HashMap k) | |
| Functor (Map k) | |
| Functor (Mealy i) | |
Defined in Development.Shake.Internal.Progress | |
| Functor f => Functor (Rec1 f) | |
| Functor (URec Char :: * -> *) | |
| Functor (URec Double :: * -> *) | |
| Functor (URec Float :: * -> *) | |
| Functor (URec Int :: * -> *) | |
| Functor (URec Word :: * -> *) | |
| Functor (URec (Ptr ()) :: * -> *) | |
| Functor (Const m :: * -> *) | Since: base-2.1 |
| (Applicative f, Monad f) => Functor (WhenMissing f x) | Since: containers-0.5.9 |
Defined in Data.IntMap.Internal Methods fmap :: (a -> b) -> WhenMissing f x a -> WhenMissing f x b # (<$) :: a -> WhenMissing f x b -> WhenMissing f x a # | |
| Functor m => Functor (ErrorT e m) | |
| Functor (RAW ro rw) | |
Defined in Development.Shake.Internal.Core.Monad | |
| Functor ((->) r :: * -> *) | Since: base-2.1 |
| Functor (K1 i c :: * -> *) | |
| (Functor f, Functor g) => Functor (f :+: g) | |
| (Functor f, Functor g) => Functor (f :*: g) | |
| (Functor f, Functor g) => Functor (Product f g) | Since: base-4.9.0.0 |
| (Functor f, Functor g) => Functor (Sum f g) | Since: base-4.9.0.0 |
| Functor f => Functor (WhenMatched f x y) | Since: containers-0.5.9 |
Defined in Data.IntMap.Internal Methods fmap :: (a -> b) -> WhenMatched f x y a -> WhenMatched f x y b # (<$) :: a -> WhenMatched f x y b -> WhenMatched f x y a # | |
| (Applicative f, Monad f) => Functor (WhenMissing f k x) | Since: containers-0.5.9 |
Defined in Data.Map.Internal Methods fmap :: (a -> b) -> WhenMissing f k x a -> WhenMissing f k x b # (<$) :: a -> WhenMissing f k x b -> WhenMissing f k x a # | |
| Functor f => Functor (M1 i c f) | |
| (Functor f, Functor g) => Functor (f :.: g) | |
| (Functor f, Functor g) => Functor (Compose f g) | Since: base-4.9.0.0 |
| Functor f => Functor (WhenMatched f k x y) | Since: containers-0.5.9 |
Defined in Data.Map.Internal Methods fmap :: (a -> b) -> WhenMatched f k x y a -> WhenMatched f k x y b # (<$) :: a -> WhenMatched f k x y b -> WhenMatched f k x y a # | |
Basic numeric class.
Methods
Unary negation.
Absolute value.
Sign of a number.
The functions abs and signum should satisfy the law:
abs x * signum x == x
For real numbers, the signum is either -1 (negative), 0 (zero)
or 1 (positive).
fromInteger :: Integer -> a #
Conversion from an Integer.
An integer literal represents the application of the function
fromInteger to the appropriate value of type Integer,
so such literals have type (.Num a) => a
Instances
The Ord class is used for totally ordered datatypes.
Instances of Ord can be derived for any user-defined
datatype whose constituent types are in Ord. The declared order
of the constructors in the data declaration determines the ordering
in derived Ord instances. The Ordering datatype allows a single
comparison to determine the precise ordering of two objects.
Minimal complete definition: either compare or <=.
Using compare can be more efficient for complex types.
Methods
compare :: a -> a -> Ordering #
(<) :: a -> a -> Bool infix 4 #
(<=) :: a -> a -> Bool infix 4 #
(>) :: a -> a -> Bool infix 4 #
Instances
| Ord Bool | |
| Ord Char | |
| Ord Double | |
| Ord Float | |
| Ord Int | |
| Ord Int8 | Since: base-2.1 |
| Ord Int16 | Since: base-2.1 |
| Ord Int32 | Since: base-2.1 |
| Ord Int64 | Since: base-2.1 |
| Ord Integer | |
| Ord Ordering | |
Defined in GHC.Classes | |
| Ord Word | |
| Ord Word8 | Since: base-2.1 |
| Ord Word16 | Since: base-2.1 |
| Ord Word32 | Since: base-2.1 |
| Ord Word64 | Since: base-2.1 |
| Ord SomeTypeRep | |
Defined in Data.Typeable.Internal Methods compare :: SomeTypeRep -> SomeTypeRep -> Ordering # (<) :: SomeTypeRep -> SomeTypeRep -> Bool # (<=) :: SomeTypeRep -> SomeTypeRep -> Bool # (>) :: SomeTypeRep -> SomeTypeRep -> Bool # (>=) :: SomeTypeRep -> SomeTypeRep -> Bool # max :: SomeTypeRep -> SomeTypeRep -> SomeTypeRep # min :: SomeTypeRep -> SomeTypeRep -> SomeTypeRep # | |
| Ord () | |
| Ord TyCon | |
| Ord BigNat | |
| Ord Void | Since: base-4.8.0.0 |
| Ord AsyncException | |
Defined in GHC.IO.Exception Methods compare :: AsyncException -> AsyncException -> Ordering # (<) :: AsyncException -> AsyncException -> Bool # (<=) :: AsyncException -> AsyncException -> Bool # (>) :: AsyncException -> AsyncException -> Bool # (>=) :: AsyncException -> AsyncException -> Bool # max :: AsyncException -> AsyncException -> AsyncException # min :: AsyncException -> AsyncException -> AsyncException # | |
| Ord ArrayException | |
Defined in GHC.IO.Exception Methods compare :: ArrayException -> ArrayException -> Ordering # (<) :: ArrayException -> ArrayException -> Bool # (<=) :: ArrayException -> ArrayException -> Bool # (>) :: ArrayException -> ArrayException -> Bool # (>=) :: ArrayException -> ArrayException -> Bool # max :: ArrayException -> ArrayException -> ArrayException # min :: ArrayException -> ArrayException -> ArrayException # | |
| Ord ExitCode | |
Defined in GHC.IO.Exception | |
| Ord BufferMode | |
Defined in GHC.IO.Handle.Types Methods compare :: BufferMode -> BufferMode -> Ordering # (<) :: BufferMode -> BufferMode -> Bool # (<=) :: BufferMode -> BufferMode -> Bool # (>) :: BufferMode -> BufferMode -> Bool # (>=) :: BufferMode -> BufferMode -> Bool # max :: BufferMode -> BufferMode -> BufferMode # min :: BufferMode -> BufferMode -> BufferMode # | |
| Ord Newline | |
| Ord NewlineMode | |
Defined in GHC.IO.Handle.Types Methods compare :: NewlineMode -> NewlineMode -> Ordering # (<) :: NewlineMode -> NewlineMode -> Bool # (<=) :: NewlineMode -> NewlineMode -> Bool # (>) :: NewlineMode -> NewlineMode -> Bool # (>=) :: NewlineMode -> NewlineMode -> Bool # max :: NewlineMode -> NewlineMode -> NewlineMode # min :: NewlineMode -> NewlineMode -> NewlineMode # | |
| Ord ErrorCall | |
| Ord ArithException | |
Defined in GHC.Exception Methods compare :: ArithException -> ArithException -> Ordering # (<) :: ArithException -> ArithException -> Bool # (<=) :: ArithException -> ArithException -> Bool # (>) :: ArithException -> ArithException -> Bool # (>=) :: ArithException -> ArithException -> Bool # max :: ArithException -> ArithException -> ArithException # min :: ArithException -> ArithException -> ArithException # | |
| Ord Fixity | |
| Ord Associativity | |
Defined in GHC.Generics Methods compare :: Associativity -> Associativity -> Ordering # (<) :: Associativity -> Associativity -> Bool # (<=) :: Associativity -> Associativity -> Bool # (>) :: Associativity -> Associativity -> Bool # (>=) :: Associativity -> Associativity -> Bool # max :: Associativity -> Associativity -> Associativity # min :: Associativity -> Associativity -> Associativity # | |
| Ord SourceUnpackedness | |
Defined in GHC.Generics Methods compare :: SourceUnpackedness -> SourceUnpackedness -> Ordering # (<) :: SourceUnpackedness -> SourceUnpackedness -> Bool # (<=) :: SourceUnpackedness -> SourceUnpackedness -> Bool # (>) :: SourceUnpackedness -> SourceUnpackedness -> Bool # (>=) :: SourceUnpackedness -> SourceUnpackedness -> Bool # max :: SourceUnpackedness -> SourceUnpackedness -> SourceUnpackedness # min :: SourceUnpackedness -> SourceUnpackedness -> SourceUnpackedness # | |
| Ord SourceStrictness | |
Defined in GHC.Generics Methods compare :: SourceStrictness -> SourceStrictness -> Ordering # (<) :: SourceStrictness -> SourceStrictness -> Bool # (<=) :: SourceStrictness -> SourceStrictness -> Bool # (>) :: SourceStrictness -> SourceStrictness -> Bool # (>=) :: SourceStrictness -> SourceStrictness -> Bool # max :: SourceStrictness -> SourceStrictness -> SourceStrictness # min :: SourceStrictness -> SourceStrictness -> SourceStrictness # | |
| Ord DecidedStrictness | |
Defined in GHC.Generics Methods compare :: DecidedStrictness -> DecidedStrictness -> Ordering # (<) :: DecidedStrictness -> DecidedStrictness -> Bool # (<=) :: DecidedStrictness -> DecidedStrictness -> Bool # (>) :: DecidedStrictness -> DecidedStrictness -> Bool # (>=) :: DecidedStrictness -> DecidedStrictness -> Bool # max :: DecidedStrictness -> DecidedStrictness -> DecidedStrictness # min :: DecidedStrictness -> DecidedStrictness -> DecidedStrictness # | |
| Ord CChar | |
| Ord CSChar | |
| Ord CUChar | |
| Ord CShort | |
| Ord CUShort | |
| Ord CInt | |
| Ord CUInt | |
| Ord CLong | |
| Ord CULong | |
| Ord CLLong | |
| Ord CULLong | |
| Ord CBool | |
| Ord CFloat | |
| Ord CDouble | |
| Ord CPtrdiff | |
Defined in Foreign.C.Types | |
| Ord CSize | |
| Ord CWchar | |
| Ord CSigAtomic | |
Defined in Foreign.C.Types Methods compare :: CSigAtomic -> CSigAtomic -> Ordering # (<) :: CSigAtomic -> CSigAtomic -> Bool # (<=) :: CSigAtomic -> CSigAtomic -> Bool # (>) :: CSigAtomic -> CSigAtomic -> Bool # (>=) :: CSigAtomic -> CSigAtomic -> Bool # max :: CSigAtomic -> CSigAtomic -> CSigAtomic # min :: CSigAtomic -> CSigAtomic -> CSigAtomic # | |
| Ord CClock | |
| Ord CTime | |
| Ord CUSeconds | |
| Ord CSUSeconds | |
Defined in Foreign.C.Types Methods compare :: CSUSeconds -> CSUSeconds -> Ordering # (<) :: CSUSeconds -> CSUSeconds -> Bool # (<=) :: CSUSeconds -> CSUSeconds -> Bool # (>) :: CSUSeconds -> CSUSeconds -> Bool # (>=) :: CSUSeconds -> CSUSeconds -> Bool # max :: CSUSeconds -> CSUSeconds -> CSUSeconds # min :: CSUSeconds -> CSUSeconds -> CSUSeconds # | |
| Ord CIntPtr | |
| Ord CUIntPtr | |
Defined in Foreign.C.Types | |
| Ord CIntMax | |
| Ord CUIntMax | |
Defined in Foreign.C.Types | |
| Ord GeneralCategory | |
Defined in GHC.Unicode Methods compare :: GeneralCategory -> GeneralCategory -> Ordering # (<) :: GeneralCategory -> GeneralCategory -> Bool # (<=) :: GeneralCategory -> GeneralCategory -> Bool # (>) :: GeneralCategory -> GeneralCategory -> Bool # (>=) :: GeneralCategory -> GeneralCategory -> Bool # max :: GeneralCategory -> GeneralCategory -> GeneralCategory # min :: GeneralCategory -> GeneralCategory -> GeneralCategory # | |
| Ord IntSet | |
| Ord ByteString | |
Defined in Data.ByteString.Internal Methods compare :: ByteString -> ByteString -> Ordering # (<) :: ByteString -> ByteString -> Bool # (<=) :: ByteString -> ByteString -> Bool # (>) :: ByteString -> ByteString -> Bool # (>=) :: ByteString -> ByteString -> Bool # max :: ByteString -> ByteString -> ByteString # min :: ByteString -> ByteString -> ByteString # | |
| Ord TimeSpec | |
Defined in System.Clock | |
| Ord XdgDirectory | |
Defined in System.Directory Methods compare :: XdgDirectory -> XdgDirectory -> Ordering # (<) :: XdgDirectory -> XdgDirectory -> Bool # (<=) :: XdgDirectory -> XdgDirectory -> Bool # (>) :: XdgDirectory -> XdgDirectory -> Bool # (>=) :: XdgDirectory -> XdgDirectory -> Bool # max :: XdgDirectory -> XdgDirectory -> XdgDirectory # min :: XdgDirectory -> XdgDirectory -> XdgDirectory # | |
| Ord FileType | |
Defined in System.Directory.Internal.Common | |
| Ord Permissions | |
Defined in System.Directory.Internal.Common Methods compare :: Permissions -> Permissions -> Ordering # (<) :: Permissions -> Permissions -> Bool # (<=) :: Permissions -> Permissions -> Bool # (>) :: Permissions -> Permissions -> Bool # (>=) :: Permissions -> Permissions -> Bool # max :: Permissions -> Permissions -> Permissions # min :: Permissions -> Permissions -> Permissions # | |
| Ord ByteArray | Non-lexicographic ordering. This compares the lengths of the byte arrays first and uses a lexicographic ordering if the lengths are equal. Subject to change between major versions. Since: primitive-0.6.3.0 |
| Ord Addr | |
| Ord EqualCost | |
Defined in Development.Shake.Internal.Rules.File | |
| Ord Rebuild | |
Defined in Development.Shake.Internal.Options | |
| Ord Lint | |
| Ord Change | |
| Ord Verbosity | |
Defined in Development.Shake.Internal.Options | |
| Ord Progress | |
Defined in Development.Shake.Internal.Progress | |
| Ord Resource | |
Defined in Development.Shake.Internal.Resource | |
| Ord CmdOption | |
Defined in Development.Shake.Internal.CmdOption | |
| Ord LocalTime | |
Defined in Data.Time.LocalTime.Internal.LocalTime | |
| Ord Pat | |
| Ord a => Ord [a] | |
| Ord a => Ord (Maybe a) | |
| Integral a => Ord (Ratio a) | Since: base-2.0.1 |
| Ord p => Ord (Par1 p) | |
| Ord a => Ord (Min a) | |
| Ord a => Ord (Max a) | |
| Ord a => Ord (First a) | |
| Ord a => Ord (Last a) | |
| Ord m => Ord (WrappedMonoid m) | |
Defined in Data.Semigroup Methods compare :: WrappedMonoid m -> WrappedMonoid m -> Ordering # (<) :: WrappedMonoid m -> WrappedMonoid m -> Bool # (<=) :: WrappedMonoid m -> WrappedMonoid m -> Bool # (>) :: WrappedMonoid m -> WrappedMonoid m -> Bool # (>=) :: WrappedMonoid m -> WrappedMonoid m -> Bool # max :: WrappedMonoid m -> WrappedMonoid m -> WrappedMonoid m # min :: WrappedMonoid m -> WrappedMonoid m -> WrappedMonoid m # | |
| Ord a => Ord (Option a) | |
Defined in Data.Semigroup | |
| Ord a => Ord (Identity a) | |
Defined in Data.Functor.Identity | |
| Ord a => Ord (Down a) | Since: base-4.6.0.0 |
| Ord a => Ord (NonEmpty a) | |
| Ord a => Ord (Vector a) | |
Defined in Data.Vector | |
| Ord a => Ord (HashSet a) | |
| Ord a => Ord (Set a) | |
| Ord a => Ord (Seq a) | |
| Ord a => Ord (IntMap a) | |
Defined in Data.IntMap.Internal | |
| Ord a => Ord (ViewL a) | |
Defined in Data.Sequence.Internal | |
| Ord a => Ord (ViewR a) | |
Defined in Data.Sequence.Internal | |
| Ord a => Ord (Hashed a) | |
Defined in Data.Hashable.Class | |
| (Ord a, PrimUnlifted a) => Ord (UnliftedArray a) | Lexicographic ordering. Subject to change between major versions. Since: primitive-0.6.4.0 |
Defined in Data.Primitive.UnliftedArray Methods compare :: UnliftedArray a -> UnliftedArray a -> Ordering # (<) :: UnliftedArray a -> UnliftedArray a -> Bool # (<=) :: UnliftedArray a -> UnliftedArray a -> Bool # (>) :: UnliftedArray a -> UnliftedArray a -> Bool # (>=) :: UnliftedArray a -> UnliftedArray a -> Bool # max :: UnliftedArray a -> UnliftedArray a -> UnliftedArray a # min :: UnliftedArray a -> UnliftedArray a -> UnliftedArray a # | |
| (Ord a, Prim a) => Ord (PrimArray a) | Lexicographic ordering. Subject to change between major versions. Since: primitive-0.6.4.0 |
Defined in Data.Primitive.PrimArray | |
| Ord a => Ord (SmallArray a) | Lexicographic ordering. Subject to change between major versions. |
Defined in Data.Primitive.SmallArray Methods compare :: SmallArray a -> SmallArray a -> Ordering # (<) :: SmallArray a -> SmallArray a -> Bool # (<=) :: SmallArray a -> SmallArray a -> Bool # (>) :: SmallArray a -> SmallArray a -> Bool # (>=) :: SmallArray a -> SmallArray a -> Bool # max :: SmallArray a -> SmallArray a -> SmallArray a # min :: SmallArray a -> SmallArray a -> SmallArray a # | |
| Ord a => Ord (Array a) | Lexicographic ordering. Subject to change between major versions. |
Defined in Data.Primitive.Array | |
| (Storable a, Ord a) => Ord (Vector a) | |
Defined in Data.Vector.Storable | |
| (Prim a, Ord a) => Ord (Vector a) | |
Defined in Data.Vector.Primitive | |
| (Ord a, Ord b) => Ord (Either a b) | |
| Ord (V1 p) | Since: base-4.9.0.0 |
| Ord (U1 p) | Since: base-4.9.0.0 |
| Ord (TypeRep a) | Since: base-4.4.0.0 |
| (Ord a, Ord b) => Ord (a, b) | |
| Ord a => Ord (Arg a b) | Since: base-4.9.0.0 |
| (Ord k, Ord v) => Ord (HashMap k v) | The order is total. Note: Because the hash is not guaranteed to be stable across library
versions, OSes, or architectures, neither is an actual order of elements in
|
Defined in Data.HashMap.Base | |
| (Ord k, Ord v) => Ord (Map k v) | |
| Ord (f p) => Ord (Rec1 f p) | |
Defined in GHC.Generics | |
| Ord (URec (Ptr ()) p) | |
Defined in GHC.Generics Methods compare :: URec (Ptr ()) p -> URec (Ptr ()) p -> Ordering # (<) :: URec (Ptr ()) p -> URec (Ptr ()) p -> Bool # (<=) :: URec (Ptr ()) p -> URec (Ptr ()) p -> Bool # (>) :: URec (Ptr ()) p -> URec (Ptr ()) p -> Bool # (>=) :: URec (Ptr ()) p -> URec (Ptr ()) p -> Bool # max :: URec (Ptr ()) p -> URec (Ptr ()) p -> URec (Ptr ()) p # min :: URec (Ptr ()) p -> URec (Ptr ()) p -> URec (Ptr ()) p # | |
| Ord (URec Char p) | |
Defined in GHC.Generics | |
| Ord (URec Double p) | |
Defined in GHC.Generics Methods compare :: URec Double p -> URec Double p -> Ordering # (<) :: URec Double p -> URec Double p -> Bool # (<=) :: URec Double p -> URec Double p -> Bool # (>) :: URec Double p -> URec Double p -> Bool # (>=) :: URec Double p -> URec Double p -> Bool # | |
| Ord (URec Float p) | |
Defined in GHC.Generics | |
| Ord (URec Int p) | |
| Ord (URec Word p) | |
Defined in GHC.Generics | |
| (Ord a, Ord b, Ord c) => Ord (a, b, c) | |
| Ord a => Ord (Const a b) | |
| Ord (a :~: b) | |
Defined in Data.Type.Equality | |
| (Ord e, Ord1 m, Ord a) => Ord (ErrorT e m a) | |
Defined in Control.Monad.Trans.Error | |
| Ord c => Ord (K1 i c p) | |
Defined in GHC.Generics | |
| (Ord (f p), Ord (g p)) => Ord ((f :+: g) p) | |
Defined in GHC.Generics | |
| (Ord (f p), Ord (g p)) => Ord ((f :*: g) p) | |
Defined in GHC.Generics | |
| (Ord a, Ord b, Ord c, Ord d) => Ord (a, b, c, d) | |
Defined in GHC.Classes | |
| (Ord1 f, Ord1 g, Ord a) => Ord (Product f g a) | Since: base-4.9.0.0 |
Defined in Data.Functor.Product Methods compare :: Product f g a -> Product f g a -> Ordering # (<) :: Product f g a -> Product f g a -> Bool # (<=) :: Product f g a -> Product f g a -> Bool # (>) :: Product f g a -> Product f g a -> Bool # (>=) :: Product f g a -> Product f g a -> Bool # | |
| (Ord1 f, Ord1 g, Ord a) => Ord (Sum f g a) | Since: base-4.9.0.0 |
| Ord (a :~~: b) | Since: base-4.10.0.0 |
| Ord (f p) => Ord (M1 i c f p) | |
| Ord (f (g p)) => Ord ((f :.: g) p) | |
Defined in GHC.Generics | |
| (Ord a, Ord b, Ord c, Ord d, Ord e) => Ord (a, b, c, d, e) | |
Defined in GHC.Classes Methods compare :: (a, b, c, d, e) -> (a, b, c, d, e) -> Ordering # (<) :: (a, b, c, d, e) -> (a, b, c, d, e) -> Bool # (<=) :: (a, b, c, d, e) -> (a, b, c, d, e) -> Bool # (>) :: (a, b, c, d, e) -> (a, b, c, d, e) -> Bool # (>=) :: (a, b, c, d, e) -> (a, b, c, d, e) -> Bool # max :: (a, b, c, d, e) -> (a, b, c, d, e) -> (a, b, c, d, e) # min :: (a, b, c, d, e) -> (a, b, c, d, e) -> (a, b, c, d, e) # | |
| (Ord1 f, Ord1 g, Ord a) => Ord (Compose f g a) | Since: base-4.9.0.0 |
Defined in Data.Functor.Compose Methods compare :: Compose f g a -> Compose f g a -> Ordering # (<) :: Compose f g a -> Compose f g a -> Bool # (<=) :: Compose f g a -> Compose f g a -> Bool # (>) :: Compose f g a -> Compose f g a -> Bool # (>=) :: Compose f g a -> Compose f g a -> Bool # | |
| (Ord a, Ord b, Ord c, Ord d, Ord e, Ord f) => Ord (a, b, c, d, e, f) | |
Defined in GHC.Classes Methods compare :: (a, b, c, d, e, f) -> (a, b, c, d, e, f) -> Ordering # (<) :: (a, b, c, d, e, f) -> (a, b, c, d, e, f) -> Bool # (<=) :: (a, b, c, d, e, f) -> (a, b, c, d, e, f) -> Bool # (>) :: (a, b, c, d, e, f) -> (a, b, c, d, e, f) -> Bool # (>=) :: (a, b, c, d, e, f) -> (a, b, c, d, e, f) -> Bool # max :: (a, b, c, d, e, f) -> (a, b, c, d, e, f) -> (a, b, c, d, e, f) # min :: (a, b, c, d, e, f) -> (a, b, c, d, e, f) -> (a, b, c, d, e, f) # | |
| (Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g) => Ord (a, b, c, d, e, f, g) | |
Defined in GHC.Classes Methods compare :: (a, b, c, d, e, f, g) -> (a, b, c, d, e, f, g) -> Ordering # (<) :: (a, b, c, d, e, f, g) -> (a, b, c, d, e, f, g) -> Bool # (<=) :: (a, b, c, d, e, f, g) -> (a, b, c, d, e, f, g) -> Bool # (>) :: (a, b, c, d, e, f, g) -> (a, b, c, d, e, f, g) -> Bool # (>=) :: (a, b, c, d, e, f, g) -> (a, b, c, d, e, f, g) -> Bool # max :: (a, b, c, d, e, f, g) -> (a, b, c, d, e, f, g) -> (a, b, c, d, e, f, g) # min :: (a, b, c, d, e, f, g) -> (a, b, c, d, e, f, g) -> (a, b, c, d, e, f, g) # | |
| (Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h) => Ord (a, b, c, d, e, f, g, h) | |
Defined in GHC.Classes Methods compare :: (a, b, c, d, e, f, g, h) -> (a, b, c, d, e, f, g, h) -> Ordering # (<) :: (a, b, c, d, e, f, g, h) -> (a, b, c, d, e, f, g, h) -> Bool # (<=) :: (a, b, c, d, e, f, g, h) -> (a, b, c, d, e, f, g, h) -> Bool # (>) :: (a, b, c, d, e, f, g, h) -> (a, b, c, d, e, f, g, h) -> Bool # (>=) :: (a, b, c, d, e, f, g, h) -> (a, b, c, d, e, f, g, h) -> Bool # max :: (a, b, c, d, e, f, g, h) -> (a, b, c, d, e, f, g, h) -> (a, b, c, d, e, f, g, h) # min :: (a, b, c, d, e, f, g, h) -> (a, b, c, d, e, f, g, h) -> (a, b, c, d, e, f, g, h) # | |
| (Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h, Ord i) => Ord (a, b, c, d, e, f, g, h, i) | |
Defined in GHC.Classes Methods compare :: (a, b, c, d, e, f, g, h, i) -> (a, b, c, d, e, f, g, h, i) -> Ordering # (<) :: (a, b, c, d, e, f, g, h, i) -> (a, b, c, d, e, f, g, h, i) -> Bool # (<=) :: (a, b, c, d, e, f, g, h, i) -> (a, b, c, d, e, f, g, h, i) -> Bool # (>) :: (a, b, c, d, e, f, g, h, i) -> (a, b, c, d, e, f, g, h, i) -> Bool # (>=) :: (a, b, c, d, e, f, g, h, i) -> (a, b, c, d, e, f, g, h, i) -> Bool # max :: (a, b, c, d, e, f, g, h, i) -> (a, b, c, d, e, f, g, h, i) -> (a, b, c, d, e, f, g, h, i) # min :: (a, b, c, d, e, f, g, h, i) -> (a, b, c, d, e, f, g, h, i) -> (a, b, c, d, e, f, g, h, i) # | |
| (Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h, Ord i, Ord j) => Ord (a, b, c, d, e, f, g, h, i, j) | |
Defined in GHC.Classes Methods compare :: (a, b, c, d, e, f, g, h, i, j) -> (a, b, c, d, e, f, g, h, i, j) -> Ordering # (<) :: (a, b, c, d, e, f, g, h, i, j) -> (a, b, c, d, e, f, g, h, i, j) -> Bool # (<=) :: (a, b, c, d, e, f, g, h, i, j) -> (a, b, c, d, e, f, g, h, i, j) -> Bool # (>) :: (a, b, c, d, e, f, g, h, i, j) -> (a, b, c, d, e, f, g, h, i, j) -> Bool # (>=) :: (a, b, c, d, e, f, g, h, i, j) -> (a, b, c, d, e, f, g, h, i, j) -> Bool # max :: (a, b, c, d, e, f, g, h, i, j) -> (a, b, c, d, e, f, g, h, i, j) -> (a, b, c, d, e, f, g, h, i, j) # min :: (a, b, c, d, e, f, g, h, i, j) -> (a, b, c, d, e, f, g, h, i, j) -> (a, b, c, d, e, f, g, h, i, j) # | |
| (Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h, Ord i, Ord j, Ord k) => Ord (a, b, c, d, e, f, g, h, i, j, k) | |
Defined in GHC.Classes Methods compare :: (a, b, c, d, e, f, g, h, i, j, k) -> (a, b, c, d, e, f, g, h, i, j, k) -> Ordering # (<) :: (a, b, c, d, e, f, g, h, i, j, k) -> (a, b, c, d, e, f, g, h, i, j, k) -> Bool # (<=) :: (a, b, c, d, e, f, g, h, i, j, k) -> (a, b, c, d, e, f, g, h, i, j, k) -> Bool # (>) :: (a, b, c, d, e, f, g, h, i, j, k) -> (a, b, c, d, e, f, g, h, i, j, k) -> Bool # (>=) :: (a, b, c, d, e, f, g, h, i, j, k) -> (a, b, c, d, e, f, g, h, i, j, k) -> Bool # max :: (a, b, c, d, e, f, g, h, i, j, k) -> (a, b, c, d, e, f, g, h, i, j, k) -> (a, b, c, d, e, f, g, h, i, j, k) # min :: (a, b, c, d, e, f, g, h, i, j, k) -> (a, b, c, d, e, f, g, h, i, j, k) -> (a, b, c, d, e, f, g, h, i, j, k) # | |
| (Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h, Ord i, Ord j, Ord k, Ord l) => Ord (a, b, c, d, e, f, g, h, i, j, k, l) | |
Defined in GHC.Classes Methods compare :: (a, b, c, d, e, f, g, h, i, j, k, l) -> (a, b, c, d, e, f, g, h, i, j, k, l) -> Ordering # (<) :: (a, b, c, d, e, f, g, h, i, j, k, l) -> (a, b, c, d, e, f, g, h, i, j, k, l) -> Bool # (<=) :: (a, b, c, d, e, f, g, h, i, j, k, l) -> (a, b, c, d, e, f, g, h, i, j, k, l) -> Bool # (>) :: (a, b, c, d, e, f, g, h, i, j, k, l) -> (a, b, c, d, e, f, g, h, i, j, k, l) -> Bool # (>=) :: (a, b, c, d, e, f, g, h, i, j, k, l) -> (a, b, c, d, e, f, g, h, i, j, k, l) -> Bool # max :: (a, b, c, d, e, f, g, h, i, j, k, l) -> (a, b, c, d, e, f, g, h, i, j, k, l) -> (a, b, c, d, e, f, g, h, i, j, k, l) # min :: (a, b, c, d, e, f, g, h, i, j, k, l) -> (a, b, c, d, e, f, g, h, i, j, k, l) -> (a, b, c, d, e, f, g, h, i, j, k, l) # | |
| (Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h, Ord i, Ord j, Ord k, Ord l, Ord m) => Ord (a, b, c, d, e, f, g, h, i, j, k, l, m) | |
Defined in GHC.Classes Methods compare :: (a, b, c, d, e, f, g, h, i, j, k, l, m) -> (a, b, c, d, e, f, g, h, i, j, k, l, m) -> Ordering # (<) :: (a, b, c, d, e, f, g, h, i, j, k, l, m) -> (a, b, c, d, e, f, g, h, i, j, k, l, m) -> Bool # (<=) :: (a, b, c, d, e, f, g, h, i, j, k, l, m) -> (a, b, c, d, e, f, g, h, i, j, k, l, m) -> Bool # (>) :: (a, b, c, d, e, f, g, h, i, j, k, l, m) -> (a, b, c, d, e, f, g, h, i, j, k, l, m) -> Bool # (>=) :: (a, b, c, d, e, f, g, h, i, j, k, l, m) -> (a, b, c, d, e, f, g, h, i, j, k, l, m) -> Bool # max :: (a, b, c, d, e, f, g, h, i, j, k, l, m) -> (a, b, c, d, e, f, g, h, i, j, k, l, m) -> (a, b, c, d, e, f, g, h, i, j, k, l, m) # min :: (a, b, c, d, e, f, g, h, i, j, k, l, m) -> (a, b, c, d, e, f, g, h, i, j, k, l, m) -> (a, b, c, d, e, f, g, h, i, j, k, l, m) # | |
| (Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h, Ord i, Ord j, Ord k, Ord l, Ord m, Ord n) => Ord (a, b, c, d, e, f, g, h, i, j, k, l, m, n) | |
Defined in GHC.Classes Methods compare :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> Ordering # (<) :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> Bool # (<=) :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> Bool # (>) :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> Bool # (>=) :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> Bool # max :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n) # min :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n) # | |
| (Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h, Ord i, Ord j, Ord k, Ord l, Ord m, Ord n, Ord o) => Ord (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) | |
Defined in GHC.Classes Methods compare :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> Ordering # (<) :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> Bool # (<=) :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> Bool # (>) :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> Bool # (>=) :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> Bool # max :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) # min :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) # | |
Parsing of Strings, producing values.
Derived instances of Read make the following assumptions, which
derived instances of Show obey:
- If the constructor is defined to be an infix operator, then the
derived
Readinstance will parse only infix applications of the constructor (not the prefix form). - Associativity is not used to reduce the occurrence of parentheses, although precedence may be.
- If the constructor is defined using record syntax, the derived
Readwill parse only the record-syntax form, and furthermore, the fields must be given in the same order as the original declaration. - The derived
Readinstance allows arbitrary Haskell whitespace between tokens of the input string. Extra parentheses are also allowed.
For example, given the declarations
infixr 5 :^: data Tree a = Leaf a | Tree a :^: Tree a
the derived instance of Read in Haskell 2010 is equivalent to
instance (Read a) => Read (Tree a) where
readsPrec d r = readParen (d > app_prec)
(\r -> [(Leaf m,t) |
("Leaf",s) <- lex r,
(m,t) <- readsPrec (app_prec+1) s]) r
++ readParen (d > up_prec)
(\r -> [(u:^:v,w) |
(u,s) <- readsPrec (up_prec+1) r,
(":^:",t) <- lex s,
(v,w) <- readsPrec (up_prec+1) t]) r
where app_prec = 10
up_prec = 5Note that right-associativity of :^: is unused.
The derived instance in GHC is equivalent to
instance (Read a) => Read (Tree a) where
readPrec = parens $ (prec app_prec $ do
Ident "Leaf" <- lexP
m <- step readPrec
return (Leaf m))
+++ (prec up_prec $ do
u <- step readPrec
Symbol ":^:" <- lexP
v <- step readPrec
return (u :^: v))
where app_prec = 10
up_prec = 5
readListPrec = readListPrecDefaultWhy do both readsPrec and readPrec exist, and why does GHC opt to
implement readPrec in derived Read instances instead of readsPrec?
The reason is that readsPrec is based on the ReadS type, and although
ReadS is mentioned in the Haskell 2010 Report, it is not a very efficient
parser data structure.
readPrec, on the other hand, is based on a much more efficient ReadPrec
datatype (a.k.a "new-style parsers"), but its definition relies on the use
of the RankNTypes language extension. Therefore, readPrec (and its
cousin, readListPrec) are marked as GHC-only. Nevertheless, it is
recommended to use readPrec instead of readsPrec whenever possible
for the efficiency improvements it brings.
As mentioned above, derived Read instances in GHC will implement
readPrec instead of readsPrec. The default implementations of
readsPrec (and its cousin, readList) will simply use readPrec under
the hood. If you are writing a Read instance by hand, it is recommended
to write it like so:
instanceReadT wherereadPrec= ...readListPrec=readListPrecDefault
Methods
Arguments
| :: Int | the operator precedence of the enclosing
context (a number from |
| -> ReadS a |
attempts to parse a value from the front of the string, returning a list of (parsed value, remaining string) pairs. If there is no successful parse, the returned list is empty.
Derived instances of Read and Show satisfy the following:
That is, readsPrec parses the string produced by
showsPrec, and delivers the value that
showsPrec started with.
Instances
| Read Bool | Since: base-2.1 |
| Read Char | Since: base-2.1 |
| Read Double | Since: base-2.1 |
| Read Float | Since: base-2.1 |
| Read Int | Since: base-2.1 |
| Read Int8 | Since: base-2.1 |
| Read Int16 | Since: base-2.1 |
| Read Int32 | Since: base-2.1 |
| Read Int64 | Since: base-2.1 |
| Read Integer | Since: base-2.1 |
| Read Ordering | Since: base-2.1 |
| Read Word | Since: base-4.5.0.0 |
| Read Word8 | Since: base-2.1 |
| Read Word16 | Since: base-2.1 |
| Read Word32 | Since: base-2.1 |
| Read Word64 | Since: base-2.1 |
| Read () | Since: base-2.1 |
| Read Void | Reading a Since: base-4.8.0.0 |
| Read ExitCode | |
| Read BufferMode | |
Defined in GHC.IO.Handle.Types Methods readsPrec :: Int -> ReadS BufferMode # readList :: ReadS [BufferMode] # readPrec :: ReadPrec BufferMode # readListPrec :: ReadPrec [BufferMode] # | |
| Read Newline | |
| Read NewlineMode | |
Defined in GHC.IO.Handle.Types Methods readsPrec :: Int -> ReadS NewlineMode # readList :: ReadS [NewlineMode] # readPrec :: ReadPrec NewlineMode # readListPrec :: ReadPrec [NewlineMode] # | |
| Read Fixity | |
| Read Associativity | |
Defined in GHC.Generics Methods readsPrec :: Int -> ReadS Associativity # readList :: ReadS [Associativity] # | |
| Read SourceUnpackedness | |
Defined in GHC.Generics Methods readsPrec :: Int -> ReadS SourceUnpackedness # readList :: ReadS [SourceUnpackedness] # | |
| Read SourceStrictness | |
Defined in GHC.Generics Methods readsPrec :: Int -> ReadS SourceStrictness # readList :: ReadS [SourceStrictness] # | |
| Read DecidedStrictness | |
Defined in GHC.Generics Methods readsPrec :: Int -> ReadS DecidedStrictness # readList :: ReadS [DecidedStrictness] # | |
| Read CChar | |
| Read CSChar | |
| Read CUChar | |
| Read CShort | |
| Read CUShort | |
| Read CInt | |
| Read CUInt | |
| Read CLong | |
| Read CULong | |
| Read CLLong | |
| Read CULLong | |
| Read CBool | |
| Read CFloat | |
| Read CDouble | |
| Read CPtrdiff | |
| Read CSize | |
| Read CWchar | |
| Read CSigAtomic | |
Defined in Foreign.C.Types Methods readsPrec :: Int -> ReadS CSigAtomic # readList :: ReadS [CSigAtomic] # readPrec :: ReadPrec CSigAtomic # readListPrec :: ReadPrec [CSigAtomic] # | |
| Read CClock | |
| Read CTime | |
| Read CUSeconds | |
| Read CSUSeconds | |
Defined in Foreign.C.Types Methods readsPrec :: Int -> ReadS CSUSeconds # readList :: ReadS [CSUSeconds] # readPrec :: ReadPrec CSUSeconds # readListPrec :: ReadPrec [CSUSeconds] # | |
| Read CIntPtr | |
| Read CUIntPtr | |
| Read CIntMax | |
| Read CUIntMax | |
| Read Lexeme | Since: base-2.1 |
| Read GeneralCategory | |
Defined in GHC.Read Methods readsPrec :: Int -> ReadS GeneralCategory # readList :: ReadS [GeneralCategory] # | |
| Read IntSet | |
| Read ByteString | |
Defined in Data.ByteString.Internal Methods readsPrec :: Int -> ReadS ByteString # readList :: ReadS [ByteString] # readPrec :: ReadPrec ByteString # readListPrec :: ReadPrec [ByteString] # | |
| Read Clock | |
| Read TimeSpec | |
| Read XdgDirectory | |
Defined in System.Directory Methods readsPrec :: Int -> ReadS XdgDirectory # readList :: ReadS [XdgDirectory] # | |
| Read FileType | |
| Read Permissions | |
Defined in System.Directory.Internal.Common Methods readsPrec :: Int -> ReadS Permissions # readList :: ReadS [Permissions] # readPrec :: ReadPrec Permissions # readListPrec :: ReadPrec [Permissions] # | |
| Read EqualCost | |
| Read Rebuild | |
| Read Lint | |
| Read Change | |
| Read Verbosity | |
| Read Progress | |
| Read a => Read [a] | Since: base-2.1 |
| Read a => Read (Maybe a) | Since: base-2.1 |
| (Integral a, Read a) => Read (Ratio a) | Since: base-2.1 |
| Read p => Read (Par1 p) | |
| Read a => Read (Complex a) | |
| Read a => Read (Min a) | |
| Read a => Read (Max a) | |
| Read a => Read (First a) | |
| Read a => Read (Last a) | |
| Read m => Read (WrappedMonoid m) | |
Defined in Data.Semigroup Methods readsPrec :: Int -> ReadS (WrappedMonoid m) # readList :: ReadS [WrappedMonoid m] # readPrec :: ReadPrec (WrappedMonoid m) # readListPrec :: ReadPrec [WrappedMonoid m] # | |
| Read a => Read (Option a) | |
| Read a => Read (Identity a) | This instance would be equivalent to the derived instances of the
Since: base-4.8.0.0 |
| Read a => Read (Down a) | Since: base-4.7.0.0 |
| Read a => Read (NonEmpty a) | |
| Read a => Read (Vector a) | |
| (Eq a, Hashable a, Read a) => Read (HashSet a) | |
| (Read a, Ord a) => Read (Set a) | |
| Read a => Read (Seq a) | |
| Read e => Read (IntMap e) | |
| Read a => Read (Tree a) | |
| Read a => Read (ViewL a) | |
| Read a => Read (ViewR a) | |
| Read a => Read (SmallArray a) | |
Defined in Data.Primitive.SmallArray Methods readsPrec :: Int -> ReadS (SmallArray a) # readList :: ReadS [SmallArray a] # readPrec :: ReadPrec (SmallArray a) # readListPrec :: ReadPrec [SmallArray a] # | |
| Read a => Read (Array a) | |
| (Read a, Storable a) => Read (Vector a) | |
| (Read a, Prim a) => Read (Vector a) | |
| (Read a, Read b) => Read (Either a b) | |
| Read (V1 p) | Since: base-4.9.0.0 |
| Read (U1 p) | Since: base-4.9.0.0 |
| (Read a, Read b) => Read (a, b) | Since: base-2.1 |
| (Ix a, Read a, Read b) => Read (Array a b) | Since: base-2.1 |
| (Read a, Read b) => Read (Arg a b) | |
| (Eq k, Hashable k, Read k, Read e) => Read (HashMap k e) | |
| (Ord k, Read k, Read e) => Read (Map k e) | |
| Read (f p) => Read (Rec1 f p) | |
| (Read a, Read b, Read c) => Read (a, b, c) | Since: base-2.1 |
| Read a => Read (Const a b) | This instance would be equivalent to the derived instances of the
Since: base-4.8.0.0 |
| a ~ b => Read (a :~: b) | Since: base-4.7.0.0 |
| (Read e, Read1 m, Read a) => Read (ErrorT e m a) | |
| Read c => Read (K1 i c p) | |
| (Read (f p), Read (g p)) => Read ((f :+: g) p) | |
| (Read (f p), Read (g p)) => Read ((f :*: g) p) | |
| (Read a, Read b, Read c, Read d) => Read (a, b, c, d) | Since: base-2.1 |
| (Read1 f, Read1 g, Read a) => Read (Product f g a) | Since: base-4.9.0.0 |
| (Read1 f, Read1 g, Read a) => Read (Sum f g a) | Since: base-4.9.0.0 |
| a ~~ b => Read (a :~~: b) | Since: base-4.10.0.0 |
| Read (f p) => Read (M1 i c f p) | |
| Read (f (g p)) => Read ((f :.: g) p) | |
| (Read a, Read b, Read c, Read d, Read e) => Read (a, b, c, d, e) | Since: base-2.1 |
| (Read1 f, Read1 g, Read a) => Read (Compose f g a) | Since: base-4.9.0.0 |
| (Read a, Read b, Read c, Read d, Read e, Read f) => Read (a, b, c, d, e, f) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g) => Read (a, b, c, d, e, f, g) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h) => Read (a, b, c, d, e, f, g, h) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i) => Read (a, b, c, d, e, f, g, h, i) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j) => Read (a, b, c, d, e, f, g, h, i, j) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k) => Read (a, b, c, d, e, f, g, h, i, j, k) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k, Read l) => Read (a, b, c, d, e, f, g, h, i, j, k, l) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k, Read l, Read m) => Read (a, b, c, d, e, f, g, h, i, j, k, l, m) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k, Read l, Read m, Read n) => Read (a, b, c, d, e, f, g, h, i, j, k, l, m, n) | Since: base-2.1 |
| (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h, Read i, Read j, Read k, Read l, Read m, Read n, Read o) => Read (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) | Since: base-2.1 |
Defined in GHC.Read | |
class (Num a, Ord a) => Real a where #
Minimal complete definition
Methods
toRational :: a -> Rational #
the rational equivalent of its real argument with full precision
Instances
class (RealFrac a, Floating a) => RealFloat a where #
Efficient, machine-independent access to the components of a floating-point number.
Minimal complete definition
floatRadix, floatDigits, floatRange, decodeFloat, encodeFloat, isNaN, isInfinite, isDenormalized, isNegativeZero, isIEEE
Methods
floatRadix :: a -> Integer #
a constant function, returning the radix of the representation
(often 2)
floatDigits :: a -> Int #
a constant function, returning the number of digits of
floatRadix in the significand
floatRange :: a -> (Int, Int) #
a constant function, returning the lowest and highest values the exponent may assume
decodeFloat :: a -> (Integer, Int) #
The function decodeFloat applied to a real floating-point
number returns the significand expressed as an Integer and an
appropriately scaled exponent (an Int). If decodeFloat x(m,n), then x is equal in value to m*b^^n, where b
is the floating-point radix, and furthermore, either m and n
are both zero or else b^(d-1) <= , where abs m < b^dd is
the value of floatDigits xdecodeFloat 0 = (0,0)decodeFloat (-0.0) = (0,0)decodeFloat xisNaN xisInfinite xTrue.
encodeFloat :: Integer -> Int -> a #
encodeFloat performs the inverse of decodeFloat in the
sense that for finite x with the exception of -0.0,
uncurry encodeFloat (decodeFloat x) = xencodeFloat m nm*b^^n (or ±Infinity if overflow
occurs); usually the closer, but if m contains too many bits,
the result may be rounded in the wrong direction.
exponent corresponds to the second component of decodeFloat.
exponent 0 = 0x,
exponent x = snd (decodeFloat x) + floatDigits xx is a finite floating-point number, it is equal in value to
significand x * b ^^ exponent xb is the
floating-point radix.
The behaviour is unspecified on infinite or NaN values.
significand :: a -> a #
The first component of decodeFloat, scaled to lie in the open
interval (-1,1), either 0.0 or of absolute value >= 1/b,
where b is the floating-point radix.
The behaviour is unspecified on infinite or NaN values.
scaleFloat :: Int -> a -> a #
multiplies a floating-point number by an integer power of the radix
True if the argument is an IEEE "not-a-number" (NaN) value
isInfinite :: a -> Bool #
True if the argument is an IEEE infinity or negative infinity
isDenormalized :: a -> Bool #
True if the argument is too small to be represented in
normalized format
isNegativeZero :: a -> Bool #
True if the argument is an IEEE negative zero
True if the argument is an IEEE floating point number
a version of arctangent taking two real floating-point arguments.
For real floating x and y, atan2 y x(x,y). atan2 y x-pi,
pi]. It follows the Common Lisp semantics for the origin when
signed zeroes are supported. atan2 y 1y in a type
that is RealFloat, should return the same value as atan yatan2 is provided, but implementors
can provide a more accurate implementation.
Instances
class (Real a, Fractional a) => RealFrac a where #
Extracting components of fractions.
Minimal complete definition
Methods
properFraction :: Integral b => a -> (b, a) #
The function properFraction takes a real fractional number x
and returns a pair (n,f) such that x = n+f, and:
nis an integral number with the same sign asx; andfis a fraction with the same type and sign asx, and with absolute value less than1.
The default definitions of the ceiling, floor, truncate
and round functions are in terms of properFraction.
truncate :: Integral b => a -> b #
truncate xx between zero and x
round :: Integral b => a -> b #
round xx;
the even integer if x is equidistant between two integers
ceiling :: Integral b => a -> b #
ceiling xx
floor :: Integral b => a -> b #
floor xx
Conversion of values to readable Strings.
Derived instances of Show have the following properties, which
are compatible with derived instances of Read:
- The result of
showis a syntactically correct Haskell expression containing only constants, given the fixity declarations in force at the point where the type is declared. It contains only the constructor names defined in the data type, parentheses, and spaces. When labelled constructor fields are used, braces, commas, field names, and equal signs are also used. - If the constructor is defined to be an infix operator, then
showsPrecwill produce infix applications of the constructor. - the representation will be enclosed in parentheses if the
precedence of the top-level constructor in
xis less thand(associativity is ignored). Thus, ifdis0then the result is never surrounded in parentheses; ifdis11it is always surrounded in parentheses, unless it is an atomic expression. - If the constructor is defined using record syntax, then
showwill produce the record-syntax form, with the fields given in the same order as the original declaration.
For example, given the declarations
infixr 5 :^: data Tree a = Leaf a | Tree a :^: Tree a
the derived instance of Show is equivalent to
instance (Show a) => Show (Tree a) where
showsPrec d (Leaf m) = showParen (d > app_prec) $
showString "Leaf " . showsPrec (app_prec+1) m
where app_prec = 10
showsPrec d (u :^: v) = showParen (d > up_prec) $
showsPrec (up_prec+1) u .
showString " :^: " .
showsPrec (up_prec+1) v
where up_prec = 5Note that right-associativity of :^: is ignored. For example,
show(Leaf 1 :^: Leaf 2 :^: Leaf 3)"Leaf 1 :^: (Leaf 2 :^: Leaf 3)".
Methods
Arguments
| :: Int | the operator precedence of the enclosing
context (a number from |
| -> a | the value to be converted to a |
| -> ShowS |
Convert a value to a readable String.
showsPrec should satisfy the law
showsPrec d x r ++ s == showsPrec d x (r ++ s)
Derived instances of Read and Show satisfy the following:
That is, readsPrec parses the string produced by
showsPrec, and delivers the value that showsPrec started with.
Instances
The class Typeable allows a concrete representation of a type to
be calculated.
Minimal complete definition
typeRep#
Class for string-like datastructures; used by the overloaded string extension (-XOverloadedStrings in GHC).
Minimal complete definition
Methods
fromString :: String -> a #
Instances
| IsString ByteString | |
Defined in Data.ByteString.Internal Methods fromString :: String -> ByteString # | |
| IsString CmdSpec | construct a Since: process-1.2.1.0 |
Defined in System.Process.Common Methods fromString :: String -> CmdSpec # | |
| a ~ Char => IsString [a] |
Since: base-2.1 |
Defined in Data.String Methods fromString :: String -> [a] # | |
| IsString a => IsString (Identity a) | |
Defined in Data.String Methods fromString :: String -> Identity a # | |
| a ~ Char => IsString (Seq a) | Since: containers-0.5.7 |
Defined in Data.Sequence.Internal Methods fromString :: String -> Seq a # | |
| (IsString a, Hashable a) => IsString (Hashed a) | |
Defined in Data.Hashable.Class Methods fromString :: String -> Hashed a # | |
| IsString a => IsString (Const a b) | Since: base-4.9.0.0 |
Defined in Data.String Methods fromString :: String -> Const a b # | |
class Functor f => Applicative (f :: * -> *) where #
A functor with application, providing operations to
A minimal complete definition must include implementations of pure
and of either <*> or liftA2. If it defines both, then they must behave
the same as their default definitions:
(<*>) =liftA2id
liftA2f x y = f<$>x<*>y
Further, any definition must satisfy the following:
- identity
pureid<*>v = v- composition
pure(.)<*>u<*>v<*>w = u<*>(v<*>w)- homomorphism
puref<*>purex =pure(f x)- interchange
u
<*>purey =pure($y)<*>u
The other methods have the following default definitions, which may be overridden with equivalent specialized implementations:
As a consequence of these laws, the Functor instance for f will satisfy
It may be useful to note that supposing
forall x y. p (q x y) = f x . g y
it follows from the above that
liftA2p (liftA2q u v) =liftA2f u .liftA2g v
If f is also a Monad, it should satisfy
(which implies that pure and <*> satisfy the applicative functor laws).
Methods
Lift a value.
(<*>) :: f (a -> b) -> f a -> f b infixl 4 #
Sequential application.
A few functors support an implementation of <*> that is more
efficient than the default one.
liftA2 :: (a -> b -> c) -> f a -> f b -> f c #
Lift a binary function to actions.
Some functors support an implementation of liftA2 that is more
efficient than the default one. In particular, if fmap is an
expensive operation, it is likely better to use liftA2 than to
fmap over the structure and then use <*>.
(<*) :: f a -> f b -> f a infixl 4 #
Sequence actions, discarding the value of the second argument.
Instances
| Applicative [] | Since: base-2.1 |
| Applicative Maybe | Since: base-2.1 |
| Applicative IO | Since: base-2.1 |
| Applicative Par1 | Since: base-4.9.0.0 |
| Applicative Complex | Since: base-4.9.0.0 |
| Applicative Min | Since: base-4.9.0.0 |
| Applicative Max | Since: base-4.9.0.0 |
| Applicative First | Since: base-4.9.0.0 |
| Applicative Last | Since: base-4.9.0.0 |
| Applicative Option | Since: base-4.9.0.0 |
| Applicative Identity | Since: base-4.8.0.0 |
| Applicative Down | Since: base-4.11.0.0 |
| Applicative ReadP | Since: base-4.6.0.0 |
| Applicative NonEmpty | Since: base-4.9.0.0 |
| Applicative Vector | |
| Applicative Seq | Since: containers-0.5.4 |
| Applicative Put | |
| Applicative Tree | |
| Applicative SmallArray | |
Defined in Data.Primitive.SmallArray Methods pure :: a -> SmallArray a # (<*>) :: SmallArray (a -> b) -> SmallArray a -> SmallArray b # liftA2 :: (a -> b -> c) -> SmallArray a -> SmallArray b -> SmallArray c # (*>) :: SmallArray a -> SmallArray b -> SmallArray b # (<*) :: SmallArray a -> SmallArray b -> SmallArray a # | |
| Applicative Array | |
| Applicative Rules | |
| Applicative Action | |
| Applicative P | Since: base-4.5.0.0 |
| Applicative (Either e) | Since: base-3.0 |
| Applicative (U1 :: * -> *) | Since: base-4.9.0.0 |
| Monoid a => Applicative ((,) a) | For tuples, the ("hello ", (+15)) <*> ("world!", 2002)
("hello world!",2017)Since: base-2.1 |
| Arrow a => Applicative (ArrowMonad a) | Since: base-4.6.0.0 |
Defined in Control.Arrow Methods pure :: a0 -> ArrowMonad a a0 # (<*>) :: ArrowMonad a (a0 -> b) -> ArrowMonad a a0 -> ArrowMonad a b # liftA2 :: (a0 -> b -> c) -> ArrowMonad a a0 -> ArrowMonad a b -> ArrowMonad a c # (*>) :: ArrowMonad a a0 -> ArrowMonad a b -> ArrowMonad a b # (<*) :: ArrowMonad a a0 -> ArrowMonad a b -> ArrowMonad a a0 # | |
| Applicative (Mealy i) | |
| Applicative f => Applicative (Rec1 f) | Since: base-4.9.0.0 |
| Monoid m => Applicative (Const m :: * -> *) | Since: base-2.0.1 |
| (Applicative f, Monad f) => Applicative (WhenMissing f x) | Equivalent to Since: containers-0.5.9 |
Defined in Data.IntMap.Internal Methods pure :: a -> WhenMissing f x a # (<*>) :: WhenMissing f x (a -> b) -> WhenMissing f x a -> WhenMissing f x b # liftA2 :: (a -> b -> c) -> WhenMissing f x a -> WhenMissing f x b -> WhenMissing f x c # (*>) :: WhenMissing f x a -> WhenMissing f x b -> WhenMissing f x b # (<*) :: WhenMissing f x a -> WhenMissing f x b -> WhenMissing f x a # | |
| (Functor m, Monad m) => Applicative (ErrorT e m) | |
Defined in Control.Monad.Trans.Error | |
| Applicative (RAW ro rw) | |
Defined in Development.Shake.Internal.Core.Monad | |
| Applicative ((->) a :: * -> *) | Since: base-2.1 |
| (Applicative f, Applicative g) => Applicative (f :*: g) | Since: base-4.9.0.0 |
| (Applicative f, Applicative g) => Applicative (Product f g) | Since: base-4.9.0.0 |
Defined in Data.Functor.Product | |
| (Monad f, Applicative f) => Applicative (WhenMatched f x y) | Equivalent to Since: containers-0.5.9 |
Defined in Data.IntMap.Internal Methods pure :: a -> WhenMatched f x y a # (<*>) :: WhenMatched f x y (a -> b) -> WhenMatched f x y a -> WhenMatched f x y b # liftA2 :: (a -> b -> c) -> WhenMatched f x y a -> WhenMatched f x y b -> WhenMatched f x y c # (*>) :: WhenMatched f x y a -> WhenMatched f x y b -> WhenMatched f x y b # (<*) :: WhenMatched f x y a -> WhenMatched f x y b -> WhenMatched f x y a # | |
| (Applicative f, Monad f) => Applicative (WhenMissing f k x) | Equivalent to Since: containers-0.5.9 |
Defined in Data.Map.Internal Methods pure :: a -> WhenMissing f k x a # (<*>) :: WhenMissing f k x (a -> b) -> WhenMissing f k x a -> WhenMissing f k x b # liftA2 :: (a -> b -> c) -> WhenMissing f k x a -> WhenMissing f k x b -> WhenMissing f k x c # (*>) :: WhenMissing f k x a -> WhenMissing f k x b -> WhenMissing f k x b # (<*) :: WhenMissing f k x a -> WhenMissing f k x b -> WhenMissing f k x a # | |
| Applicative f => Applicative (M1 i c f) | Since: base-4.9.0.0 |
| (Applicative f, Applicative g) => Applicative (f :.: g) | Since: base-4.9.0.0 |
| (Applicative f, Applicative g) => Applicative (Compose f g) | Since: base-4.9.0.0 |
Defined in Data.Functor.Compose | |
| (Monad f, Applicative f) => Applicative (WhenMatched f k x y) | Equivalent to Since: containers-0.5.9 |
Defined in Data.Map.Internal Methods pure :: a -> WhenMatched f k x y a # (<*>) :: WhenMatched f k x y (a -> b) -> WhenMatched f k x y a -> WhenMatched f k x y b # liftA2 :: (a -> b -> c) -> WhenMatched f k x y a -> WhenMatched f k x y b -> WhenMatched f k x y c # (*>) :: WhenMatched f k x y a -> WhenMatched f k x y b -> WhenMatched f k x y b # (<*) :: WhenMatched f k x y a -> WhenMatched f k x y b -> WhenMatched f k x y a # | |
class Foldable (t :: * -> *) where #
Data structures that can be folded.
For example, given a data type
data Tree a = Empty | Leaf a | Node (Tree a) a (Tree a)
a suitable instance would be
instance Foldable Tree where foldMap f Empty = mempty foldMap f (Leaf x) = f x foldMap f (Node l k r) = foldMap f l `mappend` f k `mappend` foldMap f r
This is suitable even for abstract types, as the monoid is assumed
to satisfy the monoid laws. Alternatively, one could define foldr:
instance Foldable Tree where foldr f z Empty = z foldr f z (Leaf x) = f x z foldr f z (Node l k r) = foldr f (f k (foldr f z r)) l
Foldable instances are expected to satisfy the following laws:
foldr f z t = appEndo (foldMap (Endo . f) t ) z
foldl f z t = appEndo (getDual (foldMap (Dual . Endo . flip f) t)) z
fold = foldMap id
length = getSum . foldMap (Sum . const 1)
sum, product, maximum, and minimum should all be essentially
equivalent to foldMap forms, such as
sum = getSum . foldMap Sum
but may be less defined.
If the type is also a Functor instance, it should satisfy
foldMap f = fold . fmap f
which implies that
foldMap f . fmap g = foldMap (f . g)
Methods
foldMap :: Monoid m => (a -> m) -> t a -> m #
Map each element of the structure to a monoid, and combine the results.
foldr :: (a -> b -> b) -> b -> t a -> b #
Right-associative fold of a structure.
In the case of lists, foldr, when applied to a binary operator, a
starting value (typically the right-identity of the operator), and a
list, reduces the list using the binary operator, from right to left:
foldr f z [x1, x2, ..., xn] == x1 `f` (x2 `f` ... (xn `f` z)...)
Note that, since the head of the resulting expression is produced by
an application of the operator to the first element of the list,
foldr can produce a terminating expression from an infinite list.
For a general Foldable structure this should be semantically identical
to,
foldr f z =foldrf z .toList
foldr' :: (a -> b -> b) -> b -> t a -> b #
Right-associative fold of a structure, but with strict application of the operator.
foldl :: (b -> a -> b) -> b -> t a -> b #
Left-associative fold of a structure.
In the case of lists, foldl, when applied to a binary
operator, a starting value (typically the left-identity of the operator),
and a list, reduces the list using the binary operator, from left to
right:
foldl f z [x1, x2, ..., xn] == (...((z `f` x1) `f` x2) `f`...) `f` xn
Note that to produce the outermost application of the operator the
entire input list must be traversed. This means that foldl' will
diverge if given an infinite list.
Also note that if you want an efficient left-fold, you probably want to
use foldl' instead of foldl. The reason for this is that latter does
not force the "inner" results (e.g. z in the above example)
before applying them to the operator (e.g. to f x1(). This results
in a thunk chain f x2)O(n) elements long, which then must be evaluated from
the outside-in.
For a general Foldable structure this should be semantically identical
to,
foldl f z =foldlf z .toList
foldl' :: (b -> a -> b) -> b -> t a -> b #
Left-associative fold of a structure but with strict application of the operator.
This ensures that each step of the fold is forced to weak head normal
form before being applied, avoiding the collection of thunks that would
otherwise occur. This is often what you want to strictly reduce a finite
list to a single, monolithic result (e.g. length).
For a general Foldable structure this should be semantically identical
to,
foldl f z =foldl'f z .toList
foldr1 :: (a -> a -> a) -> t a -> a #
A variant of foldr that has no base case,
and thus may only be applied to non-empty structures.
foldr1f =foldr1f .toList
foldl1 :: (a -> a -> a) -> t a -> a #
A variant of foldl that has no base case,
and thus may only be applied to non-empty structures.
foldl1f =foldl1f .toList
Test whether the structure is empty. The default implementation is optimized for structures that are similar to cons-lists, because there is no general way to do better.
Returns the size/length of a finite structure as an Int. The
default implementation is optimized for structures that are similar to
cons-lists, because there is no general way to do better.
elem :: Eq a => a -> t a -> Bool infix 4 #
Does the element occur in the structure?
maximum :: Ord a => t a -> a #
The largest element of a non-empty structure.
minimum :: Ord a => t a -> a #
The least element of a non-empty structure.
Instances
| Foldable [] | Since: base-2.1 |
Defined in Data.Foldable Methods fold :: Monoid m => [m] -> m # foldMap :: Monoid m => (a -> m) -> [a] -> m # foldr :: (a -> b -> b) -> b -> [a] -> b # foldr' :: (a -> b -> b) -> b -> [a] -> b # foldl :: (b -> a -> b) -> b -> [a] -> b # foldl' :: (b -> a -> b) -> b -> [a] -> b # foldr1 :: (a -> a -> a) -> [a] -> a # foldl1 :: (a -> a -> a) -> [a] -> a # elem :: Eq a => a -> [a] -> Bool # maximum :: Ord a => [a] -> a # | |
| Foldable Maybe | Since: base-2.1 |
Defined in Data.Foldable Methods fold :: Monoid m => Maybe m -> m # foldMap :: Monoid m => (a -> m) -> Maybe a -> m # foldr :: (a -> b -> b) -> b -> Maybe a -> b # foldr' :: (a -> b -> b) -> b -> Maybe a -> b # foldl :: (b -> a -> b) -> b -> Maybe a -> b # foldl' :: (b -> a -> b) -> b -> Maybe a -> b # foldr1 :: (a -> a -> a) -> Maybe a -> a # foldl1 :: (a -> a -> a) -> Maybe a -> a # elem :: Eq a => a -> Maybe a -> Bool # maximum :: Ord a => Maybe a -> a # minimum :: Ord a => Maybe a -> a # | |
| Foldable Par1 | |
Defined in Data.Foldable Methods fold :: Monoid m => Par1 m -> m # foldMap :: Monoid m => (a -> m) -> Par1 a -> m # foldr :: (a -> b -> b) -> b -> Par1 a -> b # foldr' :: (a -> b -> b) -> b -> Par1 a -> b # foldl :: (b -> a -> b) -> b -> Par1 a -> b # foldl' :: (b -> a -> b) -> b -> Par1 a -> b # foldr1 :: (a -> a -> a) -> Par1 a -> a # foldl1 :: (a -> a -> a) -> Par1 a -> a # elem :: Eq a => a -> Par1 a -> Bool # maximum :: Ord a => Par1 a -> a # | |
| Foldable Complex | |
Defined in Data.Complex Methods fold :: Monoid m => Complex m -> m # foldMap :: Monoid m => (a -> m) -> Complex a -> m # foldr :: (a -> b -> b) -> b -> Complex a -> b # foldr' :: (a -> b -> b) -> b -> Complex a -> b # foldl :: (b -> a -> b) -> b -> Complex a -> b # foldl' :: (b -> a -> b) -> b -> Complex a -> b # foldr1 :: (a -> a -> a) -> Complex a -> a # foldl1 :: (a -> a -> a) -> Complex a -> a # elem :: Eq a => a -> Complex a -> Bool # maximum :: Ord a => Complex a -> a # minimum :: Ord a => Complex a -> a # | |
| Foldable Min | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methods fold :: Monoid m => Min m -> m # foldMap :: Monoid m => (a -> m) -> Min a -> m # foldr :: (a -> b -> b) -> b -> Min a -> b # foldr' :: (a -> b -> b) -> b -> Min a -> b # foldl :: (b -> a -> b) -> b -> Min a -> b # foldl' :: (b -> a -> b) -> b -> Min a -> b # foldr1 :: (a -> a -> a) -> Min a -> a # foldl1 :: (a -> a -> a) -> Min a -> a # elem :: Eq a => a -> Min a -> Bool # maximum :: Ord a => Min a -> a # | |
| Foldable Max | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methods fold :: Monoid m => Max m -> m # foldMap :: Monoid m => (a -> m) -> Max a -> m # foldr :: (a -> b -> b) -> b -> Max a -> b # foldr' :: (a -> b -> b) -> b -> Max a -> b # foldl :: (b -> a -> b) -> b -> Max a -> b # foldl' :: (b -> a -> b) -> b -> Max a -> b # foldr1 :: (a -> a -> a) -> Max a -> a # foldl1 :: (a -> a -> a) -> Max a -> a # elem :: Eq a => a -> Max a -> Bool # maximum :: Ord a => Max a -> a # | |
| Foldable First | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methods fold :: Monoid m => First m -> m # foldMap :: Monoid m => (a -> m) -> First a -> m # foldr :: (a -> b -> b) -> b -> First a -> b # foldr' :: (a -> b -> b) -> b -> First a -> b # foldl :: (b -> a -> b) -> b -> First a -> b # foldl' :: (b -> a -> b) -> b -> First a -> b # foldr1 :: (a -> a -> a) -> First a -> a # foldl1 :: (a -> a -> a) -> First a -> a # elem :: Eq a => a -> First a -> Bool # maximum :: Ord a => First a -> a # minimum :: Ord a => First a -> a # | |
| Foldable Last | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methods fold :: Monoid m => Last m -> m # foldMap :: Monoid m => (a -> m) -> Last a -> m # foldr :: (a -> b -> b) -> b -> Last a -> b # foldr' :: (a -> b -> b) -> b -> Last a -> b # foldl :: (b -> a -> b) -> b -> Last a -> b # foldl' :: (b -> a -> b) -> b -> Last a -> b # foldr1 :: (a -> a -> a) -> Last a -> a # foldl1 :: (a -> a -> a) -> Last a -> a # elem :: Eq a => a -> Last a -> Bool # maximum :: Ord a => Last a -> a # | |
| Foldable Option | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methods fold :: Monoid m => Option m -> m # foldMap :: Monoid m => (a -> m) -> Option a -> m # foldr :: (a -> b -> b) -> b -> Option a -> b # foldr' :: (a -> b -> b) -> b -> Option a -> b # foldl :: (b -> a -> b) -> b -> Option a -> b # foldl' :: (b -> a -> b) -> b -> Option a -> b # foldr1 :: (a -> a -> a) -> Option a -> a # foldl1 :: (a -> a -> a) -> Option a -> a # elem :: Eq a => a -> Option a -> Bool # maximum :: Ord a => Option a -> a # minimum :: Ord a => Option a -> a # | |
| Foldable Identity | Since: base-4.8.0.0 |
Defined in Data.Functor.Identity Methods fold :: Monoid m => Identity m -> m # foldMap :: Monoid m => (a -> m) -> Identity a -> m # foldr :: (a -> b -> b) -> b -> Identity a -> b # foldr' :: (a -> b -> b) -> b -> Identity a -> b # foldl :: (b -> a -> b) -> b -> Identity a -> b # foldl' :: (b -> a -> b) -> b -> Identity a -> b # foldr1 :: (a -> a -> a) -> Identity a -> a # foldl1 :: (a -> a -> a) -> Identity a -> a # elem :: Eq a => a -> Identity a -> Bool # maximum :: Ord a => Identity a -> a # minimum :: Ord a => Identity a -> a # | |
| Foldable First | Since: base-4.8.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => First m -> m # foldMap :: Monoid m => (a -> m) -> First a -> m # foldr :: (a -> b -> b) -> b -> First a -> b # foldr' :: (a -> b -> b) -> b -> First a -> b # foldl :: (b -> a -> b) -> b -> First a -> b # foldl' :: (b -> a -> b) -> b -> First a -> b # foldr1 :: (a -> a -> a) -> First a -> a # foldl1 :: (a -> a -> a) -> First a -> a # elem :: Eq a => a -> First a -> Bool # maximum :: Ord a => First a -> a # minimum :: Ord a => First a -> a # | |
| Foldable Last | Since: base-4.8.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => Last m -> m # foldMap :: Monoid m => (a -> m) -> Last a -> m # foldr :: (a -> b -> b) -> b -> Last a -> b # foldr' :: (a -> b -> b) -> b -> Last a -> b # foldl :: (b -> a -> b) -> b -> Last a -> b # foldl' :: (b -> a -> b) -> b -> Last a -> b # foldr1 :: (a -> a -> a) -> Last a -> a # foldl1 :: (a -> a -> a) -> Last a -> a # elem :: Eq a => a -> Last a -> Bool # maximum :: Ord a => Last a -> a # | |
| Foldable Dual | Since: base-4.8.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => Dual m -> m # foldMap :: Monoid m => (a -> m) -> Dual a -> m # foldr :: (a -> b -> b) -> b -> Dual a -> b # foldr' :: (a -> b -> b) -> b -> Dual a -> b # foldl :: (b -> a -> b) -> b -> Dual a -> b # foldl' :: (b -> a -> b) -> b -> Dual a -> b # foldr1 :: (a -> a -> a) -> Dual a -> a # foldl1 :: (a -> a -> a) -> Dual a -> a # elem :: Eq a => a -> Dual a -> Bool # maximum :: Ord a => Dual a -> a # | |
| Foldable Sum | Since: base-4.8.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => Sum m -> m # foldMap :: Monoid m => (a -> m) -> Sum a -> m # foldr :: (a -> b -> b) -> b -> Sum a -> b # foldr' :: (a -> b -> b) -> b -> Sum a -> b # foldl :: (b -> a -> b) -> b -> Sum a -> b # foldl' :: (b -> a -> b) -> b -> Sum a -> b # foldr1 :: (a -> a -> a) -> Sum a -> a # foldl1 :: (a -> a -> a) -> Sum a -> a # elem :: Eq a => a -> Sum a -> Bool # maximum :: Ord a => Sum a -> a # | |
| Foldable Product | Since: base-4.8.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => Product m -> m # foldMap :: Monoid m => (a -> m) -> Product a -> m # foldr :: (a -> b -> b) -> b -> Product a -> b # foldr' :: (a -> b -> b) -> b -> Product a -> b # foldl :: (b -> a -> b) -> b -> Product a -> b # foldl' :: (b -> a -> b) -> b -> Product a -> b # foldr1 :: (a -> a -> a) -> Product a -> a # foldl1 :: (a -> a -> a) -> Product a -> a # elem :: Eq a => a -> Product a -> Bool # maximum :: Ord a => Product a -> a # minimum :: Ord a => Product a -> a # | |
| Foldable NonEmpty | Since: base-4.9.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => NonEmpty m -> m # foldMap :: Monoid m => (a -> m) -> NonEmpty a -> m # foldr :: (a -> b -> b) -> b -> NonEmpty a -> b # foldr' :: (a -> b -> b) -> b -> NonEmpty a -> b # foldl :: (b -> a -> b) -> b -> NonEmpty a -> b # foldl' :: (b -> a -> b) -> b -> NonEmpty a -> b # foldr1 :: (a -> a -> a) -> NonEmpty a -> a # foldl1 :: (a -> a -> a) -> NonEmpty a -> a # elem :: Eq a => a -> NonEmpty a -> Bool # maximum :: Ord a => NonEmpty a -> a # minimum :: Ord a => NonEmpty a -> a # | |
| Foldable Vector | |
Defined in Data.Vector Methods fold :: Monoid m => Vector m -> m # foldMap :: Monoid m => (a -> m) -> Vector a -> m # foldr :: (a -> b -> b) -> b -> Vector a -> b # foldr' :: (a -> b -> b) -> b -> Vector a -> b # foldl :: (b -> a -> b) -> b -> Vector a -> b # foldl' :: (b -> a -> b) -> b -> Vector a -> b # foldr1 :: (a -> a -> a) -> Vector a -> a # foldl1 :: (a -> a -> a) -> Vector a -> a # elem :: Eq a => a -> Vector a -> Bool # maximum :: Ord a => Vector a -> a # minimum :: Ord a => Vector a -> a # | |
| Foldable HashSet | |
Defined in Data.HashSet Methods fold :: Monoid m => HashSet m -> m # foldMap :: Monoid m => (a -> m) -> HashSet a -> m # foldr :: (a -> b -> b) -> b -> HashSet a -> b # foldr' :: (a -> b -> b) -> b -> HashSet a -> b # foldl :: (b -> a -> b) -> b -> HashSet a -> b # foldl' :: (b -> a -> b) -> b -> HashSet a -> b # foldr1 :: (a -> a -> a) -> HashSet a -> a # foldl1 :: (a -> a -> a) -> HashSet a -> a # elem :: Eq a => a -> HashSet a -> Bool # maximum :: Ord a => HashSet a -> a # minimum :: Ord a => HashSet a -> a # | |
| Foldable Set | |
Defined in Data.Set.Internal Methods fold :: Monoid m => Set m -> m # foldMap :: Monoid m => (a -> m) -> Set a -> m # foldr :: (a -> b -> b) -> b -> Set a -> b # foldr' :: (a -> b -> b) -> b -> Set a -> b # foldl :: (b -> a -> b) -> b -> Set a -> b # foldl' :: (b -> a -> b) -> b -> Set a -> b # foldr1 :: (a -> a -> a) -> Set a -> a # foldl1 :: (a -> a -> a) -> Set a -> a # elem :: Eq a => a -> Set a -> Bool # maximum :: Ord a => Set a -> a # | |
| Foldable Seq | |
Defined in Data.Sequence.Internal Methods fold :: Monoid m => Seq m -> m # foldMap :: Monoid m => (a -> m) -> Seq a -> m # foldr :: (a -> b -> b) -> b -> Seq a -> b # foldr' :: (a -> b -> b) -> b -> Seq a -> b # foldl :: (b -> a -> b) -> b -> Seq a -> b # foldl' :: (b -> a -> b) -> b -> Seq a -> b # foldr1 :: (a -> a -> a) -> Seq a -> a # foldl1 :: (a -> a -> a) -> Seq a -> a # elem :: Eq a => a -> Seq a -> Bool # maximum :: Ord a => Seq a -> a # | |
| Foldable IntMap | |
Defined in Data.IntMap.Internal Methods fold :: Monoid m => IntMap m -> m # foldMap :: Monoid m => (a -> m) -> IntMap a -> m # foldr :: (a -> b -> b) -> b -> IntMap a -> b # foldr' :: (a -> b -> b) -> b -> IntMap a -> b # foldl :: (b -> a -> b) -> b -> IntMap a -> b # foldl' :: (b -> a -> b) -> b -> IntMap a -> b # foldr1 :: (a -> a -> a) -> IntMap a -> a # foldl1 :: (a -> a -> a) -> IntMap a -> a # elem :: Eq a => a -> IntMap a -> Bool # maximum :: Ord a => IntMap a -> a # minimum :: Ord a => IntMap a -> a # | |
| Foldable Tree | |
Defined in Data.Tree Methods fold :: Monoid m => Tree m -> m # foldMap :: Monoid m => (a -> m) -> Tree a -> m # foldr :: (a -> b -> b) -> b -> Tree a -> b # foldr' :: (a -> b -> b) -> b -> Tree a -> b # foldl :: (b -> a -> b) -> b -> Tree a -> b # foldl' :: (b -> a -> b) -> b -> Tree a -> b # foldr1 :: (a -> a -> a) -> Tree a -> a # foldl1 :: (a -> a -> a) -> Tree a -> a # elem :: Eq a => a -> Tree a -> Bool # maximum :: Ord a => Tree a -> a # | |
| Foldable FingerTree | |
Defined in Data.Sequence.Internal Methods fold :: Monoid m => FingerTree m -> m # foldMap :: Monoid m => (a -> m) -> FingerTree a -> m # foldr :: (a -> b -> b) -> b -> FingerTree a -> b # foldr' :: (a -> b -> b) -> b -> FingerTree a -> b # foldl :: (b -> a -> b) -> b -> FingerTree a -> b # foldl' :: (b -> a -> b) -> b -> FingerTree a -> b # foldr1 :: (a -> a -> a) -> FingerTree a -> a # foldl1 :: (a -> a -> a) -> FingerTree a -> a # toList :: FingerTree a -> [a] # null :: FingerTree a -> Bool # length :: FingerTree a -> Int # elem :: Eq a => a -> FingerTree a -> Bool # maximum :: Ord a => FingerTree a -> a # minimum :: Ord a => FingerTree a -> a # sum :: Num a => FingerTree a -> a # product :: Num a => FingerTree a -> a # | |
| Foldable Digit | |
Defined in Data.Sequence.Internal Methods fold :: Monoid m => Digit m -> m # foldMap :: Monoid m => (a -> m) -> Digit a -> m # foldr :: (a -> b -> b) -> b -> Digit a -> b # foldr' :: (a -> b -> b) -> b -> Digit a -> b # foldl :: (b -> a -> b) -> b -> Digit a -> b # foldl' :: (b -> a -> b) -> b -> Digit a -> b # foldr1 :: (a -> a -> a) -> Digit a -> a # foldl1 :: (a -> a -> a) -> Digit a -> a # elem :: Eq a => a -> Digit a -> Bool # maximum :: Ord a => Digit a -> a # minimum :: Ord a => Digit a -> a # | |
| Foldable Node | |
Defined in Data.Sequence.Internal Methods fold :: Monoid m => Node m -> m # foldMap :: Monoid m => (a -> m) -> Node a -> m # foldr :: (a -> b -> b) -> b -> Node a -> b # foldr' :: (a -> b -> b) -> b -> Node a -> b # foldl :: (b -> a -> b) -> b -> Node a -> b # foldl' :: (b -> a -> b) -> b -> Node a -> b # foldr1 :: (a -> a -> a) -> Node a -> a # foldl1 :: (a -> a -> a) -> Node a -> a # elem :: Eq a => a -> Node a -> Bool # maximum :: Ord a => Node a -> a # | |
| Foldable Elem | |
Defined in Data.Sequence.Internal Methods fold :: Monoid m => Elem m -> m # foldMap :: Monoid m => (a -> m) -> Elem a -> m # foldr :: (a -> b -> b) -> b -> Elem a -> b # foldr' :: (a -> b -> b) -> b -> Elem a -> b # foldl :: (b -> a -> b) -> b -> Elem a -> b # foldl' :: (b -> a -> b) -> b -> Elem a -> b # foldr1 :: (a -> a -> a) -> Elem a -> a # foldl1 :: (a -> a -> a) -> Elem a -> a # elem :: Eq a => a -> Elem a -> Bool # maximum :: Ord a => Elem a -> a # | |
| Foldable ViewL | |
Defined in Data.Sequence.Internal Methods fold :: Monoid m => ViewL m -> m # foldMap :: Monoid m => (a -> m) -> ViewL a -> m # foldr :: (a -> b -> b) -> b -> ViewL a -> b # foldr' :: (a -> b -> b) -> b -> ViewL a -> b # foldl :: (b -> a -> b) -> b -> ViewL a -> b # foldl' :: (b -> a -> b) -> b -> ViewL a -> b # foldr1 :: (a -> a -> a) -> ViewL a -> a # foldl1 :: (a -> a -> a) -> ViewL a -> a # elem :: Eq a => a -> ViewL a -> Bool # maximum :: Ord a => ViewL a -> a # minimum :: Ord a => ViewL a -> a # | |
| Foldable ViewR | |
Defined in Data.Sequence.Internal Methods fold :: Monoid m => ViewR m -> m # foldMap :: Monoid m => (a -> m) -> ViewR a -> m # foldr :: (a -> b -> b) -> b -> ViewR a -> b # foldr' :: (a -> b -> b) -> b -> ViewR a -> b # foldl :: (b -> a -> b) -> b -> ViewR a -> b # foldl' :: (b -> a -> b) -> b -> ViewR a -> b # foldr1 :: (a -> a -> a) -> ViewR a -> a # foldl1 :: (a -> a -> a) -> ViewR a -> a # elem :: Eq a => a -> ViewR a -> Bool # maximum :: Ord a => ViewR a -> a # minimum :: Ord a => ViewR a -> a # | |
| Foldable Hashed | |
Defined in Data.Hashable.Class Methods fold :: Monoid m => Hashed m -> m # foldMap :: Monoid m => (a -> m) -> Hashed a -> m # foldr :: (a -> b -> b) -> b -> Hashed a -> b # foldr' :: (a -> b -> b) -> b -> Hashed a -> b # foldl :: (b -> a -> b) -> b -> Hashed a -> b # foldl' :: (b -> a -> b) -> b -> Hashed a -> b # foldr1 :: (a -> a -> a) -> Hashed a -> a # foldl1 :: (a -> a -> a) -> Hashed a -> a # elem :: Eq a => a -> Hashed a -> Bool # maximum :: Ord a => Hashed a -> a # minimum :: Ord a => Hashed a -> a # | |
| Foldable SmallArray | |
Defined in Data.Primitive.SmallArray Methods fold :: Monoid m => SmallArray m -> m # foldMap :: Monoid m => (a -> m) -> SmallArray a -> m # foldr :: (a -> b -> b) -> b -> SmallArray a -> b # foldr' :: (a -> b -> b) -> b -> SmallArray a -> b # foldl :: (b -> a -> b) -> b -> SmallArray a -> b # foldl' :: (b -> a -> b) -> b -> SmallArray a -> b # foldr1 :: (a -> a -> a) -> SmallArray a -> a # foldl1 :: (a -> a -> a) -> SmallArray a -> a # toList :: SmallArray a -> [a] # null :: SmallArray a -> Bool # length :: SmallArray a -> Int # elem :: Eq a => a -> SmallArray a -> Bool # maximum :: Ord a => SmallArray a -> a # minimum :: Ord a => SmallArray a -> a # sum :: Num a => SmallArray a -> a # product :: Num a => SmallArray a -> a # | |
| Foldable Array | |
Defined in Data.Primitive.Array Methods fold :: Monoid m => Array m -> m # foldMap :: Monoid m => (a -> m) -> Array a -> m # foldr :: (a -> b -> b) -> b -> Array a -> b # foldr' :: (a -> b -> b) -> b -> Array a -> b # foldl :: (b -> a -> b) -> b -> Array a -> b # foldl' :: (b -> a -> b) -> b -> Array a -> b # foldr1 :: (a -> a -> a) -> Array a -> a # foldl1 :: (a -> a -> a) -> Array a -> a # elem :: Eq a => a -> Array a -> Bool # maximum :: Ord a => Array a -> a # minimum :: Ord a => Array a -> a # | |
| Foldable (Either a) | Since: base-4.7.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => Either a m -> m # foldMap :: Monoid m => (a0 -> m) -> Either a a0 -> m # foldr :: (a0 -> b -> b) -> b -> Either a a0 -> b # foldr' :: (a0 -> b -> b) -> b -> Either a a0 -> b # foldl :: (b -> a0 -> b) -> b -> Either a a0 -> b # foldl' :: (b -> a0 -> b) -> b -> Either a a0 -> b # foldr1 :: (a0 -> a0 -> a0) -> Either a a0 -> a0 # foldl1 :: (a0 -> a0 -> a0) -> Either a a0 -> a0 # toList :: Either a a0 -> [a0] # length :: Either a a0 -> Int # elem :: Eq a0 => a0 -> Either a a0 -> Bool # maximum :: Ord a0 => Either a a0 -> a0 # minimum :: Ord a0 => Either a a0 -> a0 # | |
| Foldable (V1 :: * -> *) | |
Defined in Data.Foldable Methods fold :: Monoid m => V1 m -> m # foldMap :: Monoid m => (a -> m) -> V1 a -> m # foldr :: (a -> b -> b) -> b -> V1 a -> b # foldr' :: (a -> b -> b) -> b -> V1 a -> b # foldl :: (b -> a -> b) -> b -> V1 a -> b # foldl' :: (b -> a -> b) -> b -> V1 a -> b # foldr1 :: (a -> a -> a) -> V1 a -> a # foldl1 :: (a -> a -> a) -> V1 a -> a # elem :: Eq a => a -> V1 a -> Bool # maximum :: Ord a => V1 a -> a # | |
| Foldable (U1 :: * -> *) | Since: base-4.9.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => U1 m -> m # foldMap :: Monoid m => (a -> m) -> U1 a -> m # foldr :: (a -> b -> b) -> b -> U1 a -> b # foldr' :: (a -> b -> b) -> b -> U1 a -> b # foldl :: (b -> a -> b) -> b -> U1 a -> b # foldl' :: (b -> a -> b) -> b -> U1 a -> b # foldr1 :: (a -> a -> a) -> U1 a -> a # foldl1 :: (a -> a -> a) -> U1 a -> a # elem :: Eq a => a -> U1 a -> Bool # maximum :: Ord a => U1 a -> a # | |
| Foldable ((,) a) | Since: base-4.7.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => (a, m) -> m # foldMap :: Monoid m => (a0 -> m) -> (a, a0) -> m # foldr :: (a0 -> b -> b) -> b -> (a, a0) -> b # foldr' :: (a0 -> b -> b) -> b -> (a, a0) -> b # foldl :: (b -> a0 -> b) -> b -> (a, a0) -> b # foldl' :: (b -> a0 -> b) -> b -> (a, a0) -> b # foldr1 :: (a0 -> a0 -> a0) -> (a, a0) -> a0 # foldl1 :: (a0 -> a0 -> a0) -> (a, a0) -> a0 # elem :: Eq a0 => a0 -> (a, a0) -> Bool # maximum :: Ord a0 => (a, a0) -> a0 # minimum :: Ord a0 => (a, a0) -> a0 # | |
| Foldable (Array i) | Since: base-4.8.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => Array i m -> m # foldMap :: Monoid m => (a -> m) -> Array i a -> m # foldr :: (a -> b -> b) -> b -> Array i a -> b # foldr' :: (a -> b -> b) -> b -> Array i a -> b # foldl :: (b -> a -> b) -> b -> Array i a -> b # foldl' :: (b -> a -> b) -> b -> Array i a -> b # foldr1 :: (a -> a -> a) -> Array i a -> a # foldl1 :: (a -> a -> a) -> Array i a -> a # elem :: Eq a => a -> Array i a -> Bool # maximum :: Ord a => Array i a -> a # minimum :: Ord a => Array i a -> a # | |
| Foldable (Arg a) | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methods fold :: Monoid m => Arg a m -> m # foldMap :: Monoid m => (a0 -> m) -> Arg a a0 -> m # foldr :: (a0 -> b -> b) -> b -> Arg a a0 -> b # foldr' :: (a0 -> b -> b) -> b -> Arg a a0 -> b # foldl :: (b -> a0 -> b) -> b -> Arg a a0 -> b # foldl' :: (b -> a0 -> b) -> b -> Arg a a0 -> b # foldr1 :: (a0 -> a0 -> a0) -> Arg a a0 -> a0 # foldl1 :: (a0 -> a0 -> a0) -> Arg a a0 -> a0 # elem :: Eq a0 => a0 -> Arg a a0 -> Bool # maximum :: Ord a0 => Arg a a0 -> a0 # minimum :: Ord a0 => Arg a a0 -> a0 # | |
| Foldable (Proxy :: * -> *) | Since: base-4.7.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => Proxy m -> m # foldMap :: Monoid m => (a -> m) -> Proxy a -> m # foldr :: (a -> b -> b) -> b -> Proxy a -> b # foldr' :: (a -> b -> b) -> b -> Proxy a -> b # foldl :: (b -> a -> b) -> b -> Proxy a -> b # foldl' :: (b -> a -> b) -> b -> Proxy a -> b # foldr1 :: (a -> a -> a) -> Proxy a -> a # foldl1 :: (a -> a -> a) -> Proxy a -> a # elem :: Eq a => a -> Proxy a -> Bool # maximum :: Ord a => Proxy a -> a # minimum :: Ord a => Proxy a -> a # | |
| Foldable (HashMap k) | |
Defined in Data.HashMap.Base Methods fold :: Monoid m => HashMap k m -> m # foldMap :: Monoid m => (a -> m) -> HashMap k a -> m # foldr :: (a -> b -> b) -> b -> HashMap k a -> b # foldr' :: (a -> b -> b) -> b -> HashMap k a -> b # foldl :: (b -> a -> b) -> b -> HashMap k a -> b # foldl' :: (b -> a -> b) -> b -> HashMap k a -> b # foldr1 :: (a -> a -> a) -> HashMap k a -> a # foldl1 :: (a -> a -> a) -> HashMap k a -> a # toList :: HashMap k a -> [a] # length :: HashMap k a -> Int # elem :: Eq a => a -> HashMap k a -> Bool # maximum :: Ord a => HashMap k a -> a # minimum :: Ord a => HashMap k a -> a # | |
| Foldable (Map k) | |
Defined in Data.Map.Internal Methods fold :: Monoid m => Map k m -> m # foldMap :: Monoid m => (a -> m) -> Map k a -> m # foldr :: (a -> b -> b) -> b -> Map k a -> b # foldr' :: (a -> b -> b) -> b -> Map k a -> b # foldl :: (b -> a -> b) -> b -> Map k a -> b # foldl' :: (b -> a -> b) -> b -> Map k a -> b # foldr1 :: (a -> a -> a) -> Map k a -> a # foldl1 :: (a -> a -> a) -> Map k a -> a # elem :: Eq a => a -> Map k a -> Bool # maximum :: Ord a => Map k a -> a # minimum :: Ord a => Map k a -> a # | |
| Foldable f => Foldable (Rec1 f) | |
Defined in Data.Foldable Methods fold :: Monoid m => Rec1 f m -> m # foldMap :: Monoid m => (a -> m) -> Rec1 f a -> m # foldr :: (a -> b -> b) -> b -> Rec1 f a -> b # foldr' :: (a -> b -> b) -> b -> Rec1 f a -> b # foldl :: (b -> a -> b) -> b -> Rec1 f a -> b # foldl' :: (b -> a -> b) -> b -> Rec1 f a -> b # foldr1 :: (a -> a -> a) -> Rec1 f a -> a # foldl1 :: (a -> a -> a) -> Rec1 f a -> a # elem :: Eq a => a -> Rec1 f a -> Bool # maximum :: Ord a => Rec1 f a -> a # minimum :: Ord a => Rec1 f a -> a # | |
| Foldable (URec Char :: * -> *) | |
Defined in Data.Foldable Methods fold :: Monoid m => URec Char m -> m # foldMap :: Monoid m => (a -> m) -> URec Char a -> m # foldr :: (a -> b -> b) -> b -> URec Char a -> b # foldr' :: (a -> b -> b) -> b -> URec Char a -> b # foldl :: (b -> a -> b) -> b -> URec Char a -> b # foldl' :: (b -> a -> b) -> b -> URec Char a -> b # foldr1 :: (a -> a -> a) -> URec Char a -> a # foldl1 :: (a -> a -> a) -> URec Char a -> a # toList :: URec Char a -> [a] # length :: URec Char a -> Int # elem :: Eq a => a -> URec Char a -> Bool # maximum :: Ord a => URec Char a -> a # minimum :: Ord a => URec Char a -> a # | |
| Foldable (URec Double :: * -> *) | |
Defined in Data.Foldable Methods fold :: Monoid m => URec Double m -> m # foldMap :: Monoid m => (a -> m) -> URec Double a -> m # foldr :: (a -> b -> b) -> b -> URec Double a -> b # foldr' :: (a -> b -> b) -> b -> URec Double a -> b # foldl :: (b -> a -> b) -> b -> URec Double a -> b # foldl' :: (b -> a -> b) -> b -> URec Double a -> b # foldr1 :: (a -> a -> a) -> URec Double a -> a # foldl1 :: (a -> a -> a) -> URec Double a -> a # toList :: URec Double a -> [a] # null :: URec Double a -> Bool # length :: URec Double a -> Int # elem :: Eq a => a -> URec Double a -> Bool # maximum :: Ord a => URec Double a -> a # minimum :: Ord a => URec Double a -> a # | |
| Foldable (URec Float :: * -> *) | |
Defined in Data.Foldable Methods fold :: Monoid m => URec Float m -> m # foldMap :: Monoid m => (a -> m) -> URec Float a -> m # foldr :: (a -> b -> b) -> b -> URec Float a -> b # foldr' :: (a -> b -> b) -> b -> URec Float a -> b # foldl :: (b -> a -> b) -> b -> URec Float a -> b # foldl' :: (b -> a -> b) -> b -> URec Float a -> b # foldr1 :: (a -> a -> a) -> URec Float a -> a # foldl1 :: (a -> a -> a) -> URec Float a -> a # toList :: URec Float a -> [a] # null :: URec Float a -> Bool # length :: URec Float a -> Int # elem :: Eq a => a -> URec Float a -> Bool # maximum :: Ord a => URec Float a -> a # minimum :: Ord a => URec Float a -> a # | |
| Foldable (URec Int :: * -> *) | |
Defined in Data.Foldable Methods fold :: Monoid m => URec Int m -> m # foldMap :: Monoid m => (a -> m) -> URec Int a -> m # foldr :: (a -> b -> b) -> b -> URec Int a -> b # foldr' :: (a -> b -> b) -> b -> URec Int a -> b # foldl :: (b -> a -> b) -> b -> URec Int a -> b # foldl' :: (b -> a -> b) -> b -> URec Int a -> b # foldr1 :: (a -> a -> a) -> URec Int a -> a # foldl1 :: (a -> a -> a) -> URec Int a -> a # elem :: Eq a => a -> URec Int a -> Bool # maximum :: Ord a => URec Int a -> a # minimum :: Ord a => URec Int a -> a # | |
| Foldable (URec Word :: * -> *) | |
Defined in Data.Foldable Methods fold :: Monoid m => URec Word m -> m # foldMap :: Monoid m => (a -> m) -> URec Word a -> m # foldr :: (a -> b -> b) -> b -> URec Word a -> b # foldr' :: (a -> b -> b) -> b -> URec Word a -> b # foldl :: (b -> a -> b) -> b -> URec Word a -> b # foldl' :: (b -> a -> b) -> b -> URec Word a -> b # foldr1 :: (a -> a -> a) -> URec Word a -> a # foldl1 :: (a -> a -> a) -> URec Word a -> a # toList :: URec Word a -> [a] # length :: URec Word a -> Int # elem :: Eq a => a -> URec Word a -> Bool # maximum :: Ord a => URec Word a -> a # minimum :: Ord a => URec Word a -> a # | |
| Foldable (URec (Ptr ()) :: * -> *) | |
Defined in Data.Foldable Methods fold :: Monoid m => URec (Ptr ()) m -> m # foldMap :: Monoid m => (a -> m) -> URec (Ptr ()) a -> m # foldr :: (a -> b -> b) -> b -> URec (Ptr ()) a -> b # foldr' :: (a -> b -> b) -> b -> URec (Ptr ()) a -> b # foldl :: (b -> a -> b) -> b -> URec (Ptr ()) a -> b # foldl' :: (b -> a -> b) -> b -> URec (Ptr ()) a -> b # foldr1 :: (a -> a -> a) -> URec (Ptr ()) a -> a # foldl1 :: (a -> a -> a) -> URec (Ptr ()) a -> a # toList :: URec (Ptr ()) a -> [a] # null :: URec (Ptr ()) a -> Bool # length :: URec (Ptr ()) a -> Int # elem :: Eq a => a -> URec (Ptr ()) a -> Bool # maximum :: Ord a => URec (Ptr ()) a -> a # minimum :: Ord a => URec (Ptr ()) a -> a # | |
| Foldable (Const m :: * -> *) | Since: base-4.7.0.0 |
Defined in Data.Functor.Const Methods fold :: Monoid m0 => Const m m0 -> m0 # foldMap :: Monoid m0 => (a -> m0) -> Const m a -> m0 # foldr :: (a -> b -> b) -> b -> Const m a -> b # foldr' :: (a -> b -> b) -> b -> Const m a -> b # foldl :: (b -> a -> b) -> b -> Const m a -> b # foldl' :: (b -> a -> b) -> b -> Const m a -> b # foldr1 :: (a -> a -> a) -> Const m a -> a # foldl1 :: (a -> a -> a) -> Const m a -> a # elem :: Eq a => a -> Const m a -> Bool # maximum :: Ord a => Const m a -> a # minimum :: Ord a => Const m a -> a # | |
| Foldable f => Foldable (ErrorT e f) | |
Defined in Control.Monad.Trans.Error Methods fold :: Monoid m => ErrorT e f m -> m # foldMap :: Monoid m => (a -> m) -> ErrorT e f a -> m # foldr :: (a -> b -> b) -> b -> ErrorT e f a -> b # foldr' :: (a -> b -> b) -> b -> ErrorT e f a -> b # foldl :: (b -> a -> b) -> b -> ErrorT e f a -> b # foldl' :: (b -> a -> b) -> b -> ErrorT e f a -> b # foldr1 :: (a -> a -> a) -> ErrorT e f a -> a # foldl1 :: (a -> a -> a) -> ErrorT e f a -> a # toList :: ErrorT e f a -> [a] # null :: ErrorT e f a -> Bool # length :: ErrorT e f a -> Int # elem :: Eq a => a -> ErrorT e f a -> Bool # maximum :: Ord a => ErrorT e f a -> a # minimum :: Ord a => ErrorT e f a -> a # | |
| Foldable (K1 i c :: * -> *) | |
Defined in Data.Foldable Methods fold :: Monoid m => K1 i c m -> m # foldMap :: Monoid m => (a -> m) -> K1 i c a -> m # foldr :: (a -> b -> b) -> b -> K1 i c a -> b # foldr' :: (a -> b -> b) -> b -> K1 i c a -> b # foldl :: (b -> a -> b) -> b -> K1 i c a -> b # foldl' :: (b -> a -> b) -> b -> K1 i c a -> b # foldr1 :: (a -> a -> a) -> K1 i c a -> a # foldl1 :: (a -> a -> a) -> K1 i c a -> a # elem :: Eq a => a -> K1 i c a -> Bool # maximum :: Ord a => K1 i c a -> a # minimum :: Ord a => K1 i c a -> a # | |
| (Foldable f, Foldable g) => Foldable (f :+: g) | |
Defined in Data.Foldable Methods fold :: Monoid m => (f :+: g) m -> m # foldMap :: Monoid m => (a -> m) -> (f :+: g) a -> m # foldr :: (a -> b -> b) -> b -> (f :+: g) a -> b # foldr' :: (a -> b -> b) -> b -> (f :+: g) a -> b # foldl :: (b -> a -> b) -> b -> (f :+: g) a -> b # foldl' :: (b -> a -> b) -> b -> (f :+: g) a -> b # foldr1 :: (a -> a -> a) -> (f :+: g) a -> a # foldl1 :: (a -> a -> a) -> (f :+: g) a -> a # toList :: (f :+: g) a -> [a] # length :: (f :+: g) a -> Int # elem :: Eq a => a -> (f :+: g) a -> Bool # maximum :: Ord a => (f :+: g) a -> a # minimum :: Ord a => (f :+: g) a -> a # | |
| (Foldable f, Foldable g) => Foldable (f :*: g) | |
Defined in Data.Foldable Methods fold :: Monoid m => (f :*: g) m -> m # foldMap :: Monoid m => (a -> m) -> (f :*: g) a -> m # foldr :: (a -> b -> b) -> b -> (f :*: g) a -> b # foldr' :: (a -> b -> b) -> b -> (f :*: g) a -> b # foldl :: (b -> a -> b) -> b -> (f :*: g) a -> b # foldl' :: (b -> a -> b) -> b -> (f :*: g) a -> b # foldr1 :: (a -> a -> a) -> (f :*: g) a -> a # foldl1 :: (a -> a -> a) -> (f :*: g) a -> a # toList :: (f :*: g) a -> [a] # length :: (f :*: g) a -> Int # elem :: Eq a => a -> (f :*: g) a -> Bool # maximum :: Ord a => (f :*: g) a -> a # minimum :: Ord a => (f :*: g) a -> a # | |
| (Foldable f, Foldable g) => Foldable (Product f g) | Since: base-4.9.0.0 |
Defined in Data.Functor.Product Methods fold :: Monoid m => Product f g m -> m # foldMap :: Monoid m => (a -> m) -> Product f g a -> m # foldr :: (a -> b -> b) -> b -> Product f g a -> b # foldr' :: (a -> b -> b) -> b -> Product f g a -> b # foldl :: (b -> a -> b) -> b -> Product f g a -> b # foldl' :: (b -> a -> b) -> b -> Product f g a -> b # foldr1 :: (a -> a -> a) -> Product f g a -> a # foldl1 :: (a -> a -> a) -> Product f g a -> a # toList :: Product f g a -> [a] # null :: Product f g a -> Bool # length :: Product f g a -> Int # elem :: Eq a => a -> Product f g a -> Bool # maximum :: Ord a => Product f g a -> a # minimum :: Ord a => Product f g a -> a # | |
| (Foldable f, Foldable g) => Foldable (Sum f g) | Since: base-4.9.0.0 |
Defined in Data.Functor.Sum Methods fold :: Monoid m => Sum f g m -> m # foldMap :: Monoid m => (a -> m) -> Sum f g a -> m # foldr :: (a -> b -> b) -> b -> Sum f g a -> b # foldr' :: (a -> b -> b) -> b -> Sum f g a -> b # foldl :: (b -> a -> b) -> b -> Sum f g a -> b # foldl' :: (b -> a -> b) -> b -> Sum f g a -> b # foldr1 :: (a -> a -> a) -> Sum f g a -> a # foldl1 :: (a -> a -> a) -> Sum f g a -> a # elem :: Eq a => a -> Sum f g a -> Bool # maximum :: Ord a => Sum f g a -> a # minimum :: Ord a => Sum f g a -> a # | |
| Foldable f => Foldable (M1 i c f) | |
Defined in Data.Foldable Methods fold :: Monoid m => M1 i c f m -> m # foldMap :: Monoid m => (a -> m) -> M1 i c f a -> m # foldr :: (a -> b -> b) -> b -> M1 i c f a -> b # foldr' :: (a -> b -> b) -> b -> M1 i c f a -> b # foldl :: (b -> a -> b) -> b -> M1 i c f a -> b # foldl' :: (b -> a -> b) -> b -> M1 i c f a -> b # foldr1 :: (a -> a -> a) -> M1 i c f a -> a # foldl1 :: (a -> a -> a) -> M1 i c f a -> a # elem :: Eq a => a -> M1 i c f a -> Bool # maximum :: Ord a => M1 i c f a -> a # minimum :: Ord a => M1 i c f a -> a # | |
| (Foldable f, Foldable g) => Foldable (f :.: g) | |
Defined in Data.Foldable Methods fold :: Monoid m => (f :.: g) m -> m # foldMap :: Monoid m => (a -> m) -> (f :.: g) a -> m # foldr :: (a -> b -> b) -> b -> (f :.: g) a -> b # foldr' :: (a -> b -> b) -> b -> (f :.: g) a -> b # foldl :: (b -> a -> b) -> b -> (f :.: g) a -> b # foldl' :: (b -> a -> b) -> b -> (f :.: g) a -> b # foldr1 :: (a -> a -> a) -> (f :.: g) a -> a # foldl1 :: (a -> a -> a) -> (f :.: g) a -> a # toList :: (f :.: g) a -> [a] # length :: (f :.: g) a -> Int # elem :: Eq a => a -> (f :.: g) a -> Bool # maximum :: Ord a => (f :.: g) a -> a # minimum :: Ord a => (f :.: g) a -> a # | |
| (Foldable f, Foldable g) => Foldable (Compose f g) | Since: base-4.9.0.0 |
Defined in Data.Functor.Compose Methods fold :: Monoid m => Compose f g m -> m # foldMap :: Monoid m => (a -> m) -> Compose f g a -> m # foldr :: (a -> b -> b) -> b -> Compose f g a -> b # foldr' :: (a -> b -> b) -> b -> Compose f g a -> b # foldl :: (b -> a -> b) -> b -> Compose f g a -> b # foldl' :: (b -> a -> b) -> b -> Compose f g a -> b # foldr1 :: (a -> a -> a) -> Compose f g a -> a # foldl1 :: (a -> a -> a) -> Compose f g a -> a # toList :: Compose f g a -> [a] # null :: Compose f g a -> Bool # length :: Compose f g a -> Int # elem :: Eq a => a -> Compose f g a -> Bool # maximum :: Ord a => Compose f g a -> a # minimum :: Ord a => Compose f g a -> a # | |
class (Functor t, Foldable t) => Traversable (t :: * -> *) where #
Functors representing data structures that can be traversed from left to right.
A definition of traverse must satisfy the following laws:
- naturality
t .for every applicative transformationtraversef =traverse(t . f)t- identity
traverseIdentity = Identity- composition
traverse(Compose .fmapg . f) = Compose .fmap(traverseg) .traversef
A definition of sequenceA must satisfy the following laws:
- naturality
t .for every applicative transformationsequenceA=sequenceA.fmaptt- identity
sequenceA.fmapIdentity = Identity- composition
sequenceA.fmapCompose = Compose .fmapsequenceA.sequenceA
where an applicative transformation is a function
t :: (Applicative f, Applicative g) => f a -> g a
preserving the Applicative operations, i.e.
and the identity functor Identity and composition of functors Compose
are defined as
newtype Identity a = Identity a
instance Functor Identity where
fmap f (Identity x) = Identity (f x)
instance Applicative Identity where
pure x = Identity x
Identity f <*> Identity x = Identity (f x)
newtype Compose f g a = Compose (f (g a))
instance (Functor f, Functor g) => Functor (Compose f g) where
fmap f (Compose x) = Compose (fmap (fmap f) x)
instance (Applicative f, Applicative g) => Applicative (Compose f g) where
pure x = Compose (pure (pure x))
Compose f <*> Compose x = Compose ((<*>) <$> f <*> x)(The naturality law is implied by parametricity.)
Instances are similar to Functor, e.g. given a data type
data Tree a = Empty | Leaf a | Node (Tree a) a (Tree a)
a suitable instance would be
instance Traversable Tree where traverse f Empty = pure Empty traverse f (Leaf x) = Leaf <$> f x traverse f (Node l k r) = Node <$> traverse f l <*> f k <*> traverse f r
This is suitable even for abstract types, as the laws for <*>
imply a form of associativity.
The superclass instances should satisfy the following:
- In the
Functorinstance,fmapshould be equivalent to traversal with the identity applicative functor (fmapDefault). - In the
Foldableinstance,foldMapshould be equivalent to traversal with a constant applicative functor (foldMapDefault).
Methods
traverse :: Applicative f => (a -> f b) -> t a -> f (t b) #
Map each element of a structure to an action, evaluate these actions
from left to right, and collect the results. For a version that ignores
the results see traverse_.
sequenceA :: Applicative f => t (f a) -> f (t a) #
Evaluate each action in the structure from left to right, and
and collect the results. For a version that ignores the results
see sequenceA_.
mapM :: Monad m => (a -> m b) -> t a -> m (t b) #
Map each element of a structure to a monadic action, evaluate
these actions from left to right, and collect the results. For
a version that ignores the results see mapM_.
sequence :: Monad m => t (m a) -> m (t a) #
Evaluate each monadic action in the structure from left to
right, and collect the results. For a version that ignores the
results see sequence_.
Instances
class Semigroup a => Monoid a where #
The class of monoids (types with an associative binary operation that has an identity). Instances should satisfy the following laws:
x
<>mempty= xmempty<>x = xx(<>(y<>z) = (x<>y)<>zSemigrouplaw)mconcat=foldr'(<>)'mempty
The method names refer to the monoid of lists under concatenation, but there are many other instances.
Some types can be viewed as a monoid in more than one way,
e.g. both addition and multiplication on numbers.
In such cases we often define newtypes and make those instances
of Monoid, e.g. Sum and Product.
NOTE: Semigroup is a superclass of Monoid since base-4.11.0.0.
Minimal complete definition
Methods
Identity of mappend
An associative operation
NOTE: This method is redundant and has the default
implementation mappend = '(<>)'
Fold a list using the monoid.
For most types, the default definition for mconcat will be
used, but the function is included in the class definition so
that an optimized version can be provided for specific types.
Instances
| Monoid Ordering | Since: base-2.1 |
| Monoid () | Since: base-2.1 |
| Monoid IntSet | |
| Monoid ByteString | |
Defined in Data.ByteString.Internal Methods mempty :: ByteString # mappend :: ByteString -> ByteString -> ByteString # mconcat :: [ByteString] -> ByteString # | |
| Monoid Builder | |
| Monoid ByteArray | |
| Monoid CmdArgument | |
Defined in Development.Shake.Command Methods mempty :: CmdArgument # mappend :: CmdArgument -> CmdArgument -> CmdArgument # mconcat :: [CmdArgument] -> CmdArgument # | |
| Monoid Progress | |
| Monoid SRules | |
| Monoid [a] | Since: base-2.1 |
| Semigroup a => Monoid (Maybe a) | Lift a semigroup into Since 4.11.0: constraint on inner Since: base-2.1 |
| Monoid a => Monoid (IO a) | Since: base-4.9.0.0 |
| (Ord a, Bounded a) => Monoid (Min a) | Since: base-4.9.0.0 |
| (Ord a, Bounded a) => Monoid (Max a) | Since: base-4.9.0.0 |
| Monoid m => Monoid (WrappedMonoid m) | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methods mempty :: WrappedMonoid m # mappend :: WrappedMonoid m -> WrappedMonoid m -> WrappedMonoid m # mconcat :: [WrappedMonoid m] -> WrappedMonoid m # | |
| Semigroup a => Monoid (Option a) | Since: base-4.9.0.0 |
| Monoid a => Monoid (Identity a) | |
| Monoid a => Monoid (Down a) | Since: base-4.11.0.0 |
| Monoid (Vector a) | |
| (Hashable a, Eq a) => Monoid (HashSet a) | |
| Ord a => Monoid (Set a) | |
| Monoid (Seq a) | |
| Monoid (IntMap a) | |
| PrimUnlifted a => Monoid (UnliftedArray a) | Since: primitive-0.6.4.0 |
Defined in Data.Primitive.UnliftedArray Methods mempty :: UnliftedArray a # mappend :: UnliftedArray a -> UnliftedArray a -> UnliftedArray a # mconcat :: [UnliftedArray a] -> UnliftedArray a # | |
| Monoid (PrimArray a) | Since: primitive-0.6.4.0 |
| Monoid (SmallArray a) | |
Defined in Data.Primitive.SmallArray Methods mempty :: SmallArray a # mappend :: SmallArray a -> SmallArray a -> SmallArray a # mconcat :: [SmallArray a] -> SmallArray a # | |
| Monoid (Array a) | |
| (Semigroup a, Monoid a) => Monoid (Rules a) | |
| Storable a => Monoid (Vector a) | |
| Prim a => Monoid (Vector a) | |
| Monoid (MergeSet a) | |
| Monoid b => Monoid (a -> b) | Since: base-2.1 |
| (Monoid a, Monoid b) => Monoid (a, b) | Since: base-2.1 |
| (Eq k, Hashable k) => Monoid (HashMap k v) | |
| Ord k => Monoid (Map k v) | |
| (Monoid a, Monoid b, Monoid c) => Monoid (a, b, c) | Since: base-2.1 |
| Monoid a => Monoid (Const a b) | |
| (Monoid a, Monoid b, Monoid c, Monoid d) => Monoid (a, b, c, d) | Since: base-2.1 |
| (Monoid a, Monoid b, Monoid c, Monoid d, Monoid e) => Monoid (a, b, c, d, e) | Since: base-2.1 |
Instances
The character type Char is an enumeration whose values represent
Unicode (or equivalently ISO/IEC 10646) code points (i.e. characters, see
http://www.unicode.org/ for details). This set extends the ISO 8859-1
(Latin-1) character set (the first 256 characters), which is itself an extension
of the ASCII character set (the first 128 characters). A character literal in
Haskell has type Char.
To convert a Char to or from the corresponding Int value defined
by Unicode, use toEnum and fromEnum from the
Enum class respectively (or equivalently ord and chr).
Instances
Double-precision floating point numbers. It is desirable that this type be at least equal in range and precision to the IEEE double-precision type.
Instances
Single-precision floating point numbers. It is desirable that this type be at least equal in range and precision to the IEEE single-precision type.
Instances
A fixed-precision integer type with at least the range [-2^29 .. 2^29-1].
The exact range for a given implementation can be determined by using
minBound and maxBound from the Bounded class.
Instances
32-bit signed integer type
Instances
64-bit signed integer type
Instances
Invariant: Jn# and Jp# are used iff value doesn't fit in S#
Useful properties resulting from the invariants:
Instances
| Enum Integer | Since: base-2.1 |
| Eq Integer | |
| Integral Integer | Since: base-2.0.1 |
Defined in GHC.Real | |
| Num Integer | Since: base-2.1 |
| Ord Integer | |
| Read Integer | Since: base-2.1 |
| Real Integer | Since: base-2.0.1 |
Defined in GHC.Real Methods toRational :: Integer -> Rational # | |
| Show Integer | Since: base-2.1 |
| Hashable Integer | |
Defined in Data.Hashable.Class | |
The Maybe type encapsulates an optional value. A value of type
Maybe aa (represented as Just aNothing). Using Maybe is a good way to
deal with errors or exceptional cases without resorting to drastic
measures such as error.
The Maybe type is also a monad. It is a simple kind of error
monad, where all errors are represented by Nothing. A richer
error monad can be built using the Either type.
Instances
| Monad Maybe | Since: base-2.1 |
| Functor Maybe | Since: base-2.1 |
| Applicative Maybe | Since: base-2.1 |
| Foldable Maybe | Since: base-2.1 |
Defined in Data.Foldable Methods fold :: Monoid m => Maybe m -> m # foldMap :: Monoid m => (a -> m) -> Maybe a -> m # foldr :: (a -> b -> b) -> b -> Maybe a -> b # foldr' :: (a -> b -> b) -> b -> Maybe a -> b # foldl :: (b -> a -> b) -> b -> Maybe a -> b # foldl' :: (b -> a -> b) -> b -> Maybe a -> b # foldr1 :: (a -> a -> a) -> Maybe a -> a # foldl1 :: (a -> a -> a) -> Maybe a -> a # elem :: Eq a => a -> Maybe a -> Bool # maximum :: Ord a => Maybe a -> a # minimum :: Ord a => Maybe a -> a # | |
| Traversable Maybe | Since: base-2.1 |
| Alternative Maybe | Since: base-2.1 |
| MonadPlus Maybe | Since: base-2.1 |
| Hashable1 Maybe | |
Defined in Data.Hashable.Class | |
| MonadBase Maybe Maybe | |
Defined in Control.Monad.Base | |
| MonadBaseControl Maybe Maybe | |
| Eq a => Eq (Maybe a) | |
| Ord a => Ord (Maybe a) | |
| Read a => Read (Maybe a) | Since: base-2.1 |
| Show a => Show (Maybe a) | |
| Generic (Maybe a) | |
| Semigroup a => Semigroup (Maybe a) | Since: base-4.9.0.0 |
| Semigroup a => Monoid (Maybe a) | Lift a semigroup into Since 4.11.0: constraint on inner Since: base-2.1 |
| SingKind a => SingKind (Maybe a) | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
| Hashable a => Hashable (Maybe a) | |
Defined in Data.Hashable.Class | |
| IsCmdArgument a => IsCmdArgument (Maybe a) | |
Defined in Development.Shake.Command Methods toCmdArgument :: Maybe a -> CmdArgument # | |
| Generic1 Maybe | |
| SingI (Nothing :: Maybe a) | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
| SingI a2 => SingI (Just a2 :: Maybe a1) | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
| type StM Maybe a | |
Defined in Control.Monad.Trans.Control | |
| type Rep (Maybe a) | |
| data Sing (b :: Maybe a) | |
| type DemoteRep (Maybe a) | |
Defined in GHC.Generics | |
| type Rep1 Maybe | |
Instances
| Bounded Ordering | Since: base-2.1 |
| Enum Ordering | Since: base-2.1 |
| Eq Ordering | |
| Ord Ordering | |
Defined in GHC.Classes | |
| Read Ordering | Since: base-2.1 |
| Show Ordering | |
| Generic Ordering | |
| Semigroup Ordering | Since: base-4.9.0.0 |
| Monoid Ordering | Since: base-2.1 |
| Hashable Ordering | |
Defined in Data.Hashable.Class | |
| type Rep Ordering | |
A value of type IO aa.
There is really only one way to "perform" an I/O action: bind it to
Main.main in your program. When your program is run, the I/O will
be performed. It isn't possible to perform I/O from an arbitrary
function, unless that function is itself in the IO monad and called
at some point, directly or indirectly, from Main.main.
IO is a monad, so IO actions can be combined using either the do-notation
or the >> and >>= operations from the Monad class.
Instances
| Monad IO | Since: base-2.1 |
| Functor IO | Since: base-2.1 |
| Applicative IO | Since: base-2.1 |
| MonadIO IO | Since: base-4.9.0.0 |
Defined in Control.Monad.IO.Class | |
| Alternative IO | Since: base-4.9.0.0 |
| MonadPlus IO | Since: base-4.9.0.0 |
| PrimMonad IO | |
| PrimBase IO | |
| MonadBase IO IO | |
Defined in Control.Monad.Base | |
| MonadBaseControl IO IO | |
| Semigroup a => Semigroup (IO a) | Since: base-4.10.0.0 |
| Monoid a => Monoid (IO a) | Since: base-4.9.0.0 |
| CmdResult r => CmdArguments (IO r) | |
Defined in Development.Shake.Command Methods cmdArguments :: CmdArgument -> IO r # | |
| type PrimState IO | |
Defined in Control.Monad.Primitive | |
| type StM IO a | |
Defined in Control.Monad.Trans.Control | |
Instances
8-bit unsigned integer type
Instances
32-bit unsigned integer type
Instances
64-bit unsigned integer type
Instances
The Either type represents values with two possibilities: a value of
type Either a bLeft aRight b
The Either type is sometimes used to represent a value which is
either correct or an error; by convention, the Left constructor is
used to hold an error value and the Right constructor is used to
hold a correct value (mnemonic: "right" also means "correct").
Examples
The type Either String IntString or an Int. The Left constructor can be used only on
Strings, and the Right constructor can be used only on Ints:
>>>let s = Left "foo" :: Either String Int>>>sLeft "foo">>>let n = Right 3 :: Either String Int>>>nRight 3>>>:type ss :: Either String Int>>>:type nn :: Either String Int
The fmap from our Functor instance will ignore Left values, but
will apply the supplied function to values contained in a Right:
>>>let s = Left "foo" :: Either String Int>>>let n = Right 3 :: Either String Int>>>fmap (*2) sLeft "foo">>>fmap (*2) nRight 6
The Monad instance for Either allows us to chain together multiple
actions which may fail, and fail overall if any of the individual
steps failed. First we'll write a function that can either parse an
Int from a Char, or fail.
>>>import Data.Char ( digitToInt, isDigit )>>>:{let parseEither :: Char -> Either String Int parseEither c | isDigit c = Right (digitToInt c) | otherwise = Left "parse error">>>:}
The following should work, since both '1' and '2' can be
parsed as Ints.
>>>:{let parseMultiple :: Either String Int parseMultiple = do x <- parseEither '1' y <- parseEither '2' return (x + y)>>>:}
>>>parseMultipleRight 3
But the following should fail overall, since the first operation where
we attempt to parse 'm' as an Int will fail:
>>>:{let parseMultiple :: Either String Int parseMultiple = do x <- parseEither 'm' y <- parseEither '2' return (x + y)>>>:}
>>>parseMultipleLeft "parse error"
Instances
class Monad m => MonadIO (m :: * -> *) where #
Monads in which IO computations may be embedded.
Any monad built by applying a sequence of monad transformers to the
IO monad will be an instance of this class.
Instances should satisfy the following laws, which state that liftIO
is a transformer of monads:
Minimal complete definition
Instances
| MonadIO IO | Since: base-4.9.0.0 |
Defined in Control.Monad.IO.Class | |
| MonadIO Rules | |
Defined in Development.Shake.Internal.Core.Rules | |
| MonadIO Action | |
Defined in Development.Shake.Internal.Core.Types | |
| (Error e, MonadIO m) => MonadIO (ErrorT e m) | |
Defined in Control.Monad.Trans.Error | |
| MonadIO (RAW ro rw) | |
Defined in Development.Shake.Internal.Core.Monad | |
unless :: Applicative f => Bool -> f () -> f () #
The reverse of when.
replicateM_ :: Applicative m => Int -> m a -> m () #
Like replicateM, but discards the result.
replicateM :: Applicative m => Int -> m a -> m [a] #
replicateM n actn times,
gathering the results.
foldM_ :: (Foldable t, Monad m) => (b -> a -> m b) -> b -> t a -> m () #
Like foldM, but discards the result.
foldM :: (Foldable t, Monad m) => (b -> a -> m b) -> b -> t a -> m b #
The foldM function is analogous to foldl, except that its result is
encapsulated in a monad. Note that foldM works from left-to-right over
the list arguments. This could be an issue where ( and the `folded
function' are not commutative.>>)
foldM f a1 [x1, x2, ..., xm] == do a2 <- f a1 x1 a3 <- f a2 x2 ... f am xm
If right-to-left evaluation is required, the input list should be reversed.
zipWithM_ :: Applicative m => (a -> b -> m c) -> [a] -> [b] -> m () #
zipWithM :: Applicative m => (a -> b -> m c) -> [a] -> [b] -> m [c] #
mapAndUnzipM :: Applicative m => (a -> m (b, c)) -> [a] -> m ([b], [c]) #
The mapAndUnzipM function maps its first argument over a list, returning
the result as a pair of lists. This function is mainly used with complicated
data structures or a state-transforming monad.
forever :: Applicative f => f a -> f b #
forever act
(>=>) :: Monad m => (a -> m b) -> (b -> m c) -> a -> m c infixr 1 #
Left-to-right Kleisli composition of monads.
filterM :: Applicative m => (a -> m Bool) -> [a] -> m [a] #
This generalizes the list-based filter function.
isSubsequenceOf :: Eq a => [a] -> [a] -> Bool #
The isSubsequenceOf function takes two lists and returns True if all
the elements of the first list occur, in order, in the second. The
elements do not have to occur consecutively.
isSubsequenceOf x yelem x (subsequences y)
Examples
>>>isSubsequenceOf "GHC" "The Glorious Haskell Compiler"True>>>isSubsequenceOf ['a','d'..'z'] ['a'..'z']True>>>isSubsequenceOf [1..10] [10,9..0]False
Since: base-4.8.0.0
mapAccumR :: Traversable t => (a -> b -> (a, c)) -> a -> t b -> (a, t c) #
mapAccumL :: Traversable t => (a -> b -> (a, c)) -> a -> t b -> (a, t c) #
forM :: (Traversable t, Monad m) => t a -> (a -> m b) -> m (t b) #
for :: (Traversable t, Applicative f) => t a -> (a -> f b) -> f (t b) #
first :: Arrow a => a b c -> a (b, d) (c, d) #
Send the first component of the input through the argument arrow, and copy the rest unchanged to the output.
second :: Arrow a => a b c -> a (d, b) (d, c) #
A mirror image of first.
The default definition may be overridden with a more efficient version if desired.
(***) :: Arrow a => a b c -> a b' c' -> a (b, b') (c, c') infixr 3 #
Split the input between the two argument arrows and combine their output. Note that this is in general not a functor.
The default definition may be overridden with a more efficient version if desired.
(&&&) :: Arrow a => a b c -> a b c' -> a b (c, c') infixr 3 #
Fanout: send the input to both argument arrows and combine their output.
The default definition may be overridden with a more efficient version if desired.
catchIOError :: IO a -> (IOError -> IO a) -> IO a #
The catchIOError function establishes a handler that receives any
IOError raised in the action protected by catchIOError.
An IOError is caught by
the most recent handler established by one of the exception handling
functions. These handlers are
not selective: all IOErrors are caught. Exception propagation
must be explicitly provided in a handler by re-raising any unwanted
exceptions. For example, in
f = catchIOError g (\e -> if IO.isEOFError e then return [] else ioError e)
the function f returns [] when an end-of-file exception
(cf. isEOFError) occurs in g; otherwise, the
exception is propagated to the next outer handler.
When an exception propagates outside the main program, the Haskell
system prints the associated IOError value and exits the program.
Non-I/O exceptions are not caught by this variant; to catch all
exceptions, use catch from Control.Exception.
Since: base-4.4.0.0
modifyIOError :: (IOError -> IOError) -> IO a -> IO a #
Catch any IOError that occurs in the computation and throw a
modified version.
ioeSetFileName :: IOError -> FilePath -> IOError #
ioeSetHandle :: IOError -> Handle -> IOError #
ioeSetLocation :: IOError -> String -> IOError #
ioeSetErrorString :: IOError -> String -> IOError #
ioeSetErrorType :: IOError -> IOErrorType -> IOError #
ioeGetFileName :: IOError -> Maybe FilePath #
ioeGetHandle :: IOError -> Maybe Handle #
ioeGetLocation :: IOError -> String #
ioeGetErrorString :: IOError -> String #
ioeGetErrorType :: IOError -> IOErrorType #
isUserErrorType :: IOErrorType -> Bool #
I/O error that is programmer-defined.
isPermissionErrorType :: IOErrorType -> Bool #
I/O error where the operation failed because the user does not have sufficient operating system privilege to perform that operation.
isIllegalOperationErrorType :: IOErrorType -> Bool #
I/O error where the operation is not possible.
isEOFErrorType :: IOErrorType -> Bool #
I/O error where the operation failed because the end of file has been reached.
isFullErrorType :: IOErrorType -> Bool #
I/O error where the operation failed because the device is full.
isAlreadyInUseErrorType :: IOErrorType -> Bool #
I/O error where the operation failed because one of its arguments is a single-use resource, which is already being used.
isDoesNotExistErrorType :: IOErrorType -> Bool #
I/O error where the operation failed because one of its arguments does not exist.
isAlreadyExistsErrorType :: IOErrorType -> Bool #
I/O error where the operation failed because one of its arguments already exists.
userErrorType :: IOErrorType #
I/O error that is programmer-defined.
permissionErrorType :: IOErrorType #
I/O error where the operation failed because the user does not have sufficient operating system privilege to perform that operation.
illegalOperationErrorType :: IOErrorType #
I/O error where the operation is not possible.
I/O error where the operation failed because the end of file has been reached.
fullErrorType :: IOErrorType #
I/O error where the operation failed because the device is full.
alreadyInUseErrorType :: IOErrorType #
I/O error where the operation failed because one of its arguments is a single-use resource, which is already being used.
doesNotExistErrorType :: IOErrorType #
I/O error where the operation failed because one of its arguments does not exist.
alreadyExistsErrorType :: IOErrorType #
I/O error where the operation failed because one of its arguments already exists.
isUserError :: IOError -> Bool #
A programmer-defined error value constructed using userError.
isPermissionError :: IOError -> Bool #
An error indicating that an IO operation failed because
the user does not have sufficient operating system privilege
to perform that operation.
isIllegalOperation :: IOError -> Bool #
An error indicating that an IO operation failed because
the operation was not possible.
Any computation which returns an IO result may fail with
isIllegalOperation. In some cases, an implementation will not be
able to distinguish between the possible error causes. In this case
it should fail with isIllegalOperation.
isEOFError :: IOError -> Bool #
An error indicating that an IO operation failed because
the end of file has been reached.
isFullError :: IOError -> Bool #
An error indicating that an IO operation failed because
the device is full.
isAlreadyInUseError :: IOError -> Bool #
An error indicating that an IO operation failed because
one of its arguments is a single-use resource, which is already
being used (for example, opening the same file twice for writing
might give this error).
isDoesNotExistError :: IOError -> Bool #
An error indicating that an IO operation failed because
one of its arguments does not exist.
isAlreadyExistsError :: IOError -> Bool #
An error indicating that an IO operation failed because
one of its arguments already exists.
mkIOError :: IOErrorType -> String -> Maybe Handle -> Maybe FilePath -> IOError #
Construct an IOError of the given type where the second argument
describes the error location and the third and fourth argument
contain the file handle and file path of the file involved in the
error if applicable.
tryIOError :: IO a -> IO (Either IOError a) #
The construct tryIOError comp exposes IO errors which occur within a
computation, and which are not fully handled.
Non-I/O exceptions are not caught by this variant; to catch all
exceptions, use try from Control.Exception.
Since: base-4.4.0.0
data IOErrorType #
An abstract type that contains a value for each variant of IOError.
Instances
| Eq IOErrorType | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
| Show IOErrorType | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception Methods showsPrec :: Int -> IOErrorType -> ShowS # show :: IOErrorType -> String # showList :: [IOErrorType] -> ShowS # | |
File and directory names are values of type String, whose precise
meaning is operating system dependent. Files can be opened, yielding a
handle which can then be used to operate on the contents of that file.
data IOException #
Exceptions that occur in the IO monad.
An IOException records a more specific error type, a descriptive
string and maybe the handle that was used when the error was
flagged.
Instances
| Eq IOException | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
| Show IOException | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception Methods showsPrec :: Int -> IOException -> ShowS # show :: IOException -> String # showList :: [IOException] -> ShowS # | |
| Exception IOException | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception Methods toException :: IOException -> SomeException # fromException :: SomeException -> Maybe IOException # displayException :: IOException -> String # | |
| Error IOException | |
Defined in Control.Monad.Trans.Error | |
type IOError = IOException #
class (Typeable e, Show e) => Exception e where #
Any type that you wish to throw or catch as an exception must be an
instance of the Exception class. The simplest case is a new exception
type directly below the root:
data MyException = ThisException | ThatException
deriving Show
instance Exception MyExceptionThe default method definitions in the Exception class do what we need
in this case. You can now throw and catch ThisException and
ThatException as exceptions:
*Main> throw ThisException `catch` \e -> putStrLn ("Caught " ++ show (e :: MyException))
Caught ThisException
In more complicated examples, you may wish to define a whole hierarchy of exceptions:
---------------------------------------------------------------------
-- Make the root exception type for all the exceptions in a compiler
data SomeCompilerException = forall e . Exception e => SomeCompilerException e
instance Show SomeCompilerException where
show (SomeCompilerException e) = show e
instance Exception SomeCompilerException
compilerExceptionToException :: Exception e => e -> SomeException
compilerExceptionToException = toException . SomeCompilerException
compilerExceptionFromException :: Exception e => SomeException -> Maybe e
compilerExceptionFromException x = do
SomeCompilerException a <- fromException x
cast a
---------------------------------------------------------------------
-- Make a subhierarchy for exceptions in the frontend of the compiler
data SomeFrontendException = forall e . Exception e => SomeFrontendException e
instance Show SomeFrontendException where
show (SomeFrontendException e) = show e
instance Exception SomeFrontendException where
toException = compilerExceptionToException
fromException = compilerExceptionFromException
frontendExceptionToException :: Exception e => e -> SomeException
frontendExceptionToException = toException . SomeFrontendException
frontendExceptionFromException :: Exception e => SomeException -> Maybe e
frontendExceptionFromException x = do
SomeFrontendException a <- fromException x
cast a
---------------------------------------------------------------------
-- Make an exception type for a particular frontend compiler exception
data MismatchedParentheses = MismatchedParentheses
deriving Show
instance Exception MismatchedParentheses where
toException = frontendExceptionToException
fromException = frontendExceptionFromExceptionWe can now catch a MismatchedParentheses exception as
MismatchedParentheses, SomeFrontendException or
SomeCompilerException, but not other types, e.g. IOException:
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: MismatchedParentheses))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: SomeFrontendException))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: SomeCompilerException))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: IOException))
*** Exception: MismatchedParentheses
Methods
toException :: e -> SomeException #
fromException :: SomeException -> Maybe e #
displayException :: e -> String #
Render this exception value in a human-friendly manner.
Default implementation: show
Since: base-4.8.0.0
Instances
minimumBy :: Foldable t => (a -> a -> Ordering) -> t a -> a #
The least element of a non-empty structure with respect to the given comparison function.
maximumBy :: Foldable t => (a -> a -> Ordering) -> t a -> a #
The largest element of a non-empty structure with respect to the given comparison function.
all :: Foldable t => (a -> Bool) -> t a -> Bool #
Determines whether all elements of the structure satisfy the predicate.
any :: Foldable t => (a -> Bool) -> t a -> Bool #
Determines whether any element of the structure satisfies the predicate.
concatMap :: Foldable t => (a -> [b]) -> t a -> [b] #
Map a function over all the elements of a container and concatenate the resulting lists.
asum :: (Foldable t, Alternative f) => t (f a) -> f a #
sequence_ :: (Foldable t, Monad m) => t (m a) -> m () #
Evaluate each monadic action in the structure from left to right,
and ignore the results. For a version that doesn't ignore the
results see sequence.
As of base 4.8.0.0, sequence_ is just sequenceA_, specialized
to Monad.
sequenceA_ :: (Foldable t, Applicative f) => t (f a) -> f () #
Evaluate each action in the structure from left to right, and
ignore the results. For a version that doesn't ignore the results
see sequenceA.
for_ :: (Foldable t, Applicative f) => t a -> (a -> f b) -> f () #
traverse_ :: (Foldable t, Applicative f) => (a -> f b) -> t a -> f () #
Map each element of a structure to an action, evaluate these
actions from left to right, and ignore the results. For a version
that doesn't ignore the results see traverse.
unfoldr :: (b -> Maybe (a, b)) -> b -> [a] #
The unfoldr function is a `dual' to foldr: while foldr
reduces a list to a summary value, unfoldr builds a list from
a seed value. The function takes the element and returns Nothing
if it is done producing the list or returns Just (a,b), in which
case, a is a prepended to the list and b is used as the next
element in a recursive call. For example,
iterate f == unfoldr (\x -> Just (x, f x))
In some cases, unfoldr can undo a foldr operation:
unfoldr f' (foldr f z xs) == xs
if the following holds:
f' (f x y) = Just (x,y) f' z = Nothing
A simple use of unfoldr:
>>>unfoldr (\b -> if b == 0 then Nothing else Just (b, b-1)) 10[10,9,8,7,6,5,4,3,2,1]
sortOn :: Ord b => (a -> b) -> [a] -> [a] #
Sort a list by comparing the results of a key function applied to each
element. sortOn f is equivalent to sortBy (comparing f), but has the
performance advantage of only evaluating f once for each element in the
input list. This is called the decorate-sort-undecorate paradigm, or
Schwartzian transform.
Elements are arranged from from lowest to highest, keeping duplicates in the order they appeared in the input.
>>>sortOn fst [(2, "world"), (4, "!"), (1, "Hello")][(1,"Hello"),(2,"world"),(4,"!")]
Since: base-4.8.0.0
The sort function implements a stable sorting algorithm.
It is a special case of sortBy, which allows the programmer to supply
their own comparison function.
Elements are arranged from from lowest to highest, keeping duplicates in the order they appeared in the input.
>>>sort [1,6,4,3,2,5][1,2,3,4,5,6]
permutations :: [a] -> [[a]] #
The permutations function returns the list of all permutations of the argument.
>>>permutations "abc"["abc","bac","cba","bca","cab","acb"]
subsequences :: [a] -> [[a]] #
The subsequences function returns the list of all subsequences of the argument.
>>>subsequences "abc"["","a","b","ab","c","ac","bc","abc"]
group :: Eq a => [a] -> [[a]] #
The group function takes a list and returns a list of lists such
that the concatenation of the result is equal to the argument. Moreover,
each sublist in the result contains only equal elements. For example,
>>>group "Mississippi"["M","i","ss","i","ss","i","pp","i"]
It is a special case of groupBy, which allows the programmer to supply
their own equality test.
deleteFirstsBy :: (a -> a -> Bool) -> [a] -> [a] -> [a] #
The deleteFirstsBy function takes a predicate and two lists and
returns the first list with the first occurrence of each element of
the second list removed.
zipWith7 :: (a -> b -> c -> d -> e -> f -> g -> h) -> [a] -> [b] -> [c] -> [d] -> [e] -> [f] -> [g] -> [h] #
genericReplicate :: Integral i => i -> a -> [a] #
The genericReplicate function is an overloaded version of replicate,
which accepts any Integral value as the number of repetitions to make.
genericIndex :: Integral i => [a] -> i -> a #
The genericIndex function is an overloaded version of !!, which
accepts any Integral value as the index.
genericSplitAt :: Integral i => i -> [a] -> ([a], [a]) #
The genericSplitAt function is an overloaded version of splitAt, which
accepts any Integral value as the position at which to split.
genericDrop :: Integral i => i -> [a] -> [a] #
The genericDrop function is an overloaded version of drop, which
accepts any Integral value as the number of elements to drop.
genericTake :: Integral i => i -> [a] -> [a] #
The genericTake function is an overloaded version of take, which
accepts any Integral value as the number of elements to take.
genericLength :: Num i => [a] -> i #
The genericLength function is an overloaded version of length. In
particular, instead of returning an Int, it returns any type which is
an instance of Num. It is, however, less efficient than length.
insert :: Ord a => a -> [a] -> [a] #
The insert function takes an element and a list and inserts the
element into the list at the first position where it is less
than or equal to the next element. In particular, if the list
is sorted before the call, the result will also be sorted.
It is a special case of insertBy, which allows the programmer to
supply their own comparison function.
>>>insert 4 [1,2,3,5,6,7][1,2,3,4,5,6,7]
partition :: (a -> Bool) -> [a] -> ([a], [a]) #
The partition function takes a predicate a list and returns
the pair of lists of elements which do and do not satisfy the
predicate, respectively; i.e.,
partition p xs == (filter p xs, filter (not . p) xs)
>>>partition (`elem` "aeiou") "Hello World!"("eoo","Hll Wrld!")
The transpose function transposes the rows and columns of its argument.
For example,
>>>transpose [[1,2,3],[4,5,6]][[1,4],[2,5],[3,6]]
If some of the rows are shorter than the following rows, their elements are skipped:
>>>transpose [[10,11],[20],[],[30,31,32]][[10,20,30],[11,31],[32]]
intersperse :: a -> [a] -> [a] #
The intersperse function takes an element and a list and
`intersperses' that element between the elements of the list.
For example,
>>>intersperse ',' "abcde""a,b,c,d,e"
intersectBy :: (a -> a -> Bool) -> [a] -> [a] -> [a] #
The intersectBy function is the non-overloaded version of intersect.
intersect :: Eq a => [a] -> [a] -> [a] #
The intersect function takes the list intersection of two lists.
For example,
>>>[1,2,3,4] `intersect` [2,4,6,8][2,4]
If the first list contains duplicates, so will the result.
>>>[1,2,2,3,4] `intersect` [6,4,4,2][2,2,4]
It is a special case of intersectBy, which allows the programmer to
supply their own equality test. If the element is found in both the first
and the second list, the element from the first list will be used.
union :: Eq a => [a] -> [a] -> [a] #
The union function returns the list union of the two lists.
For example,
>>>"dog" `union` "cow""dogcw"
Duplicates, and elements of the first list, are removed from the
the second list, but if the first list contains duplicates, so will
the result.
It is a special case of unionBy, which allows the programmer to supply
their own equality test.
(\\) :: Eq a => [a] -> [a] -> [a] infix 5 #
The \\ function is list difference (non-associative).
In the result of xs \\ ys, the first occurrence of each element of
ys in turn (if any) has been removed from xs. Thus
(xs ++ ys) \\ xs == ys.
>>>"Hello World!" \\ "ell W""Hoorld!"
It is a special case of deleteFirstsBy, which allows the programmer
to supply their own equality test.
O(n^2). The nub function removes duplicate elements from a list.
In particular, it keeps only the first occurrence of each element.
(The name nub means `essence'.)
It is a special case of nubBy, which allows the programmer to supply
their own equality test.
>>>nub [1,2,3,4,3,2,1,2,4,3,5][1,2,3,4,5]
isSuffixOf :: Eq a => [a] -> [a] -> Bool #
The isSuffixOf function takes two lists and returns True iff
the first list is a suffix of the second. The second list must be
finite.
>>>"ld!" `isSuffixOf` "Hello World!"True
>>>"World" `isSuffixOf` "Hello World!"False
isPrefixOf :: Eq a => [a] -> [a] -> Bool #
The isPrefixOf function takes two lists and returns True
iff the first list is a prefix of the second.
>>>"Hello" `isPrefixOf` "Hello World!"True
>>>"Hello" `isPrefixOf` "Wello Horld!"False
findIndices :: (a -> Bool) -> [a] -> [Int] #
The findIndices function extends findIndex, by returning the
indices of all elements satisfying the predicate, in ascending order.
>>>findIndices (`elem` "aeiou") "Hello World!"[1,4,7]
elemIndices :: Eq a => a -> [a] -> [Int] #
The elemIndices function extends elemIndex, by returning the
indices of all elements equal to the query element, in ascending order.
>>>elemIndices 'o' "Hello World"[4,7]
stripPrefix :: Eq a => [a] -> [a] -> Maybe [a] #
The stripPrefix function drops the given prefix from a list.
It returns Nothing if the list did not start with the prefix
given, or Just the list after the prefix, if it does.
>>>stripPrefix "foo" "foobar"Just "bar"
>>>stripPrefix "foo" "foo"Just ""
>>>stripPrefix "foo" "barfoo"Nothing
>>>stripPrefix "foo" "barfoobaz"Nothing
dropWhileEnd :: (a -> Bool) -> [a] -> [a] #
The dropWhileEnd function drops the largest suffix of a list
in which the given predicate holds for all elements. For example:
>>>dropWhileEnd isSpace "foo\n""foo"
>>>dropWhileEnd isSpace "foo bar""foo bar"
dropWhileEnd isSpace ("foo\n" ++ undefined) == "foo" ++ undefinedSince: base-4.5.0.0
partitionEithers :: [Either a b] -> ([a], [b]) #
Partitions a list of Either into two lists.
All the Left elements are extracted, in order, to the first
component of the output. Similarly the Right elements are extracted
to the second component of the output.
Examples
Basic usage:
>>>let list = [ Left "foo", Right 3, Left "bar", Right 7, Left "baz" ]>>>partitionEithers list(["foo","bar","baz"],[3,7])
The pair returned by partitionEithers x(:lefts x, rights x)
>>>let list = [ Left "foo", Right 3, Left "bar", Right 7, Left "baz" ]>>>partitionEithers list == (lefts list, rights list)True
either :: (a -> c) -> (b -> c) -> Either a b -> c #
Case analysis for the Either type.
If the value is Left aa;
if it is Right bb.
Examples
We create two values of type Either String IntLeft constructor and another using the Right constructor. Then
we apply "either" the length function (if we have a String)
or the "times-two" function (if we have an Int):
>>>let s = Left "foo" :: Either String Int>>>let n = Right 3 :: Either String Int>>>either length (*2) s3>>>either length (*2) n6
comparing :: Ord a => (b -> a) -> b -> b -> Ordering #
comparing p x y = compare (p x) (p y)
Useful combinator for use in conjunction with the xxxBy family
of functions from Data.List, for example:
... sortBy (comparing fst) ...
The Down type allows you to reverse sort order conveniently. A value of type
Down aa (represented as Down aa has an Ordthen sortWith by Down x
Since: base-4.6.0.0
Constructors
| Down a |
Instances
| Monad Down | Since: base-4.11.0.0 |
| Functor Down | Since: base-4.11.0.0 |
| Applicative Down | Since: base-4.11.0.0 |
| Eq a => Eq (Down a) | |
| Num a => Num (Down a) | Since: base-4.11.0.0 |
| Ord a => Ord (Down a) | Since: base-4.6.0.0 |
| Read a => Read (Down a) | Since: base-4.7.0.0 |
| Show a => Show (Down a) | Since: base-4.7.0.0 |
| Semigroup a => Semigroup (Down a) | Since: base-4.11.0.0 |
| Monoid a => Monoid (Down a) | Since: base-4.11.0.0 |
The member functions of this class facilitate writing values of primitive types to raw memory (which may have been allocated with the above mentioned routines) and reading values from blocks of raw memory. The class, furthermore, includes support for computing the storage requirements and alignment restrictions of storable types.
Memory addresses are represented as values of type Ptr aa which is an instance of class Storable. The type argument to
Ptr helps provide some valuable type safety in FFI code (you can't
mix pointers of different types without an explicit cast), while
helping the Haskell type system figure out which marshalling method is
needed for a given pointer.
All marshalling between Haskell and a foreign language ultimately
boils down to translating Haskell data structures into the binary
representation of a corresponding data structure of the foreign
language and vice versa. To code this marshalling in Haskell, it is
necessary to manipulate primitive data types stored in unstructured
memory blocks. The class Storable facilitates this manipulation on
all types for which it is instantiated, which are the standard basic
types of Haskell, the fixed size Int types (Int8, Int16,
Int32, Int64), the fixed size Word types (Word8, Word16,
Word32, Word64), StablePtr, all types from Foreign.C.Types,
as well as Ptr.
Minimal complete definition
sizeOf, alignment, (peek | peekElemOff | peekByteOff), (poke | pokeElemOff | pokeByteOff)
Instances
The lex function reads a single lexeme from the input, discarding
initial white space, and returning the characters that constitute the
lexeme. If the input string contains only white space, lex returns a
single successful `lexeme' consisting of the empty string. (Thus
lex "" = [("","")]lex fails (i.e. returns []).
This lexer is not completely faithful to the Haskell lexical syntax in the following respects:
- Qualified names are not handled properly
- Octal and hexadecimal numerics are not recognized as a single token
- Comments are not treated properly
Case analysis for the Bool type. bool x y px
when p is False, and evaluates to y when p is True.
This is equivalent to if p then y else x; that is, one can
think of it as an if-then-else construct with its arguments
reordered.
Examples
Basic usage:
>>>bool "foo" "bar" True"bar">>>bool "foo" "bar" False"foo"
Confirm that bool x y pif p then y else x are
equivalent:
>>>let p = True; x = "bar"; y = "foo">>>bool x y p == if p then y else xTrue>>>let p = False>>>bool x y p == if p then y else xTrue
Since: base-4.7.0.0
void :: Functor f => f a -> f () #
void valueIO action.
Examples
Replace the contents of a Maybe Int
>>>void NothingNothing>>>void (Just 3)Just ()
Replace the contents of an Either Int IntEither Int '()'
>>>void (Left 8675309)Left 8675309>>>void (Right 8675309)Right ()
Replace every element of a list with unit:
>>>void [1,2,3][(),(),()]
Replace the second element of a pair with unit:
>>>void (1,2)(1,())
Discard the result of an IO action:
>>>mapM print [1,2]1 2 [(),()]>>>void $ mapM print [1,2]1 2
(<$>) :: Functor f => (a -> b) -> f a -> f b infixl 4 #
An infix synonym for fmap.
The name of this operator is an allusion to $.
Note the similarities between their types:
($) :: (a -> b) -> a -> b (<$>) :: Functor f => (a -> b) -> f a -> f b
Whereas $ is function application, <$> is function
application lifted over a Functor.
Examples
Convert from a Maybe IntMaybe Stringshow:
>>>show <$> NothingNothing>>>show <$> Just 3Just "3"
Convert from an Either Int IntEither IntString using show:
>>>show <$> Left 17Left 17>>>show <$> Right 17Right "17"
Double each element of a list:
>>>(*2) <$> [1,2,3][2,4,6]
Apply even to the second element of a pair:
>>>even <$> (2,2)(2,True)
lcm :: Integral a => a -> a -> a #
lcm x yx and y divide.
gcd :: Integral a => a -> a -> a #
gcd x yx and y of which
every common factor of x and y is also a factor; for example
gcd 4 2 = 2gcd (-4) 6 = 2gcd 0 44. gcd 0 00.
(That is, the common divisor that is "greatest" in the divisibility
preordering.)
Note: Since for signed fixed-width integer types, abs minBound < 0minBound0 or minBound
(^^) :: (Fractional a, Integral b) => a -> b -> a infixr 8 #
raise a number to an integral power
showString :: String -> ShowS #
utility function converting a String to a show function that
simply prepends the string unchanged.
utility function converting a Char to a show function that
simply prepends the character unchanged.
unzip :: [(a, b)] -> ([a], [b]) #
unzip transforms a list of pairs into a list of first components
and a list of second components.
(!!) :: [a] -> Int -> a infixl 9 #
List index (subscript) operator, starting from 0.
It is an instance of the more general genericIndex,
which takes an index of any integral type.
lookup :: Eq a => a -> [(a, b)] -> Maybe b #
lookup key assocs looks up a key in an association list.
break :: (a -> Bool) -> [a] -> ([a], [a]) #
break, applied to a predicate p and a list xs, returns a tuple where
first element is longest prefix (possibly empty) of xs of elements that
do not satisfy p and second element is the remainder of the list:
break (> 3) [1,2,3,4,1,2,3,4] == ([1,2,3],[4,1,2,3,4]) break (< 9) [1,2,3] == ([],[1,2,3]) break (> 9) [1,2,3] == ([1,2,3],[])
span :: (a -> Bool) -> [a] -> ([a], [a]) #
span, applied to a predicate p and a list xs, returns a tuple where
first element is longest prefix (possibly empty) of xs of elements that
satisfy p and second element is the remainder of the list:
span (< 3) [1,2,3,4,1,2,3,4] == ([1,2],[3,4,1,2,3,4]) span (< 9) [1,2,3] == ([1,2,3],[]) span (< 0) [1,2,3] == ([],[1,2,3])
splitAt :: Int -> [a] -> ([a], [a]) #
splitAt n xs returns a tuple where first element is xs prefix of
length n and second element is the remainder of the list:
splitAt 6 "Hello World!" == ("Hello ","World!")
splitAt 3 [1,2,3,4,5] == ([1,2,3],[4,5])
splitAt 1 [1,2,3] == ([1],[2,3])
splitAt 3 [1,2,3] == ([1,2,3],[])
splitAt 4 [1,2,3] == ([1,2,3],[])
splitAt 0 [1,2,3] == ([],[1,2,3])
splitAt (-1) [1,2,3] == ([],[1,2,3])It is equivalent to ( when take n xs, drop n xs)n is not _|_
(splitAt _|_ xs = _|_).
splitAt is an instance of the more general genericSplitAt,
in which n may be of any integral type.
drop n xs returns the suffix of xs
after the first n elements, or [] if n > :length xs
drop 6 "Hello World!" == "World!" drop 3 [1,2,3,4,5] == [4,5] drop 3 [1,2] == [] drop 3 [] == [] drop (-1) [1,2] == [1,2] drop 0 [1,2] == [1,2]
It is an instance of the more general genericDrop,
in which n may be of any integral type.
take n, applied to a list xs, returns the prefix of xs
of length n, or xs itself if n > :length xs
take 5 "Hello World!" == "Hello" take 3 [1,2,3,4,5] == [1,2,3] take 3 [1,2] == [1,2] take 3 [] == [] take (-1) [1,2] == [] take 0 [1,2] == []
It is an instance of the more general genericTake,
in which n may be of any integral type.
takeWhile :: (a -> Bool) -> [a] -> [a] #
takeWhile, applied to a predicate p and a list xs, returns the
longest prefix (possibly empty) of xs of elements that satisfy p:
takeWhile (< 3) [1,2,3,4,1,2,3,4] == [1,2] takeWhile (< 9) [1,2,3] == [1,2,3] takeWhile (< 0) [1,2,3] == []
cycle ties a finite list into a circular one, or equivalently,
the infinite repetition of the original list. It is the identity
on infinite lists.
replicate :: Int -> a -> [a] #
replicate n x is a list of length n with x the value of
every element.
It is an instance of the more general genericReplicate,
in which n may be of any integral type.
iterate' :: (a -> a) -> a -> [a] #
'iterate\'' is the strict version of iterate.
It ensures that the result of each application of force to weak head normal form before proceeding.
Return all the elements of a list except the last one. The list must be non-empty.
mapMaybe :: (a -> Maybe b) -> [a] -> [b] #
The mapMaybe function is a version of map which can throw
out elements. In particular, the functional argument returns
something of type Maybe bNothing, no element
is added on to the result list. If it is Just bb is
included in the result list.
Examples
Using mapMaybe f xcatMaybes $ map f x
>>>import Text.Read ( readMaybe )>>>let readMaybeInt = readMaybe :: String -> Maybe Int>>>mapMaybe readMaybeInt ["1", "Foo", "3"][1,3]>>>catMaybes $ map readMaybeInt ["1", "Foo", "3"][1,3]
If we map the Just constructor, the entire list should be returned:
>>>mapMaybe Just [1,2,3][1,2,3]
catMaybes :: [Maybe a] -> [a] #
The catMaybes function takes a list of Maybes and returns
a list of all the Just values.
Examples
Basic usage:
>>>catMaybes [Just 1, Nothing, Just 3][1,3]
When constructing a list of Maybe values, catMaybes can be used
to return all of the "success" results (if the list is the result
of a map, then mapMaybe would be more appropriate):
>>>import Text.Read ( readMaybe )>>>[readMaybe x :: Maybe Int | x <- ["1", "Foo", "3"] ][Just 1,Nothing,Just 3]>>>catMaybes $ [readMaybe x :: Maybe Int | x <- ["1", "Foo", "3"] ][1,3]
listToMaybe :: [a] -> Maybe a #
The listToMaybe function returns Nothing on an empty list
or Just aa is the first element of the list.
Examples
Basic usage:
>>>listToMaybe []Nothing
>>>listToMaybe [9]Just 9
>>>listToMaybe [1,2,3]Just 1
Composing maybeToList with listToMaybe should be the identity
on singleton/empty lists:
>>>maybeToList $ listToMaybe [5][5]>>>maybeToList $ listToMaybe [][]
But not on lists with more than one element:
>>>maybeToList $ listToMaybe [1,2,3][1]
maybeToList :: Maybe a -> [a] #
The maybeToList function returns an empty list when given
Nothing or a singleton list when not given Nothing.
Examples
Basic usage:
>>>maybeToList (Just 7)[7]
>>>maybeToList Nothing[]
One can use maybeToList to avoid pattern matching when combined
with a function that (safely) works on lists:
>>>import Text.Read ( readMaybe )>>>sum $ maybeToList (readMaybe "3")3>>>sum $ maybeToList (readMaybe "")0
fromMaybe :: a -> Maybe a -> a #
The fromMaybe function takes a default value and and Maybe
value. If the Maybe is Nothing, it returns the default values;
otherwise, it returns the value contained in the Maybe.
Examples
Basic usage:
>>>fromMaybe "" (Just "Hello, World!")"Hello, World!"
>>>fromMaybe "" Nothing""
Read an integer from a string using readMaybe. If we fail to
parse an integer, we want to return 0 by default:
>>>import Text.Read ( readMaybe )>>>fromMaybe 0 (readMaybe "5")5>>>fromMaybe 0 (readMaybe "")0
maybe :: b -> (a -> b) -> Maybe a -> b #
The maybe function takes a default value, a function, and a Maybe
value. If the Maybe value is Nothing, the function returns the
default value. Otherwise, it applies the function to the value inside
the Just and returns the result.
Examples
Basic usage:
>>>maybe False odd (Just 3)True
>>>maybe False odd NothingFalse
Read an integer from a string using readMaybe. If we succeed,
return twice the integer; that is, apply (*2) to it. If instead
we fail to parse an integer, return 0 by default:
>>>import Text.Read ( readMaybe )>>>maybe 0 (*2) (readMaybe "5")10>>>maybe 0 (*2) (readMaybe "")0
Apply show to a Maybe Int. If we have Just n, we want to show
the underlying Int n. But if we have Nothing, we return the
empty string instead of (for example) "Nothing":
>>>maybe "" show (Just 5)"5">>>maybe "" show Nothing""
uncurry :: (a -> b -> c) -> (a, b) -> c #
uncurry converts a curried function to a function on pairs.
Examples
>>>uncurry (+) (1,2)3
>>>uncurry ($) (show, 1)"1"
>>>map (uncurry max) [(1,2), (3,4), (6,8)][2,4,8]
until :: (a -> Bool) -> (a -> a) -> a -> a #
until p ff until p holds.
($!) :: (a -> b) -> a -> b infixr 0 #
Strict (call-by-value) application operator. It takes a function and an argument, evaluates the argument to weak head normal form (WHNF), then calls the function with that value.
flip :: (a -> b -> c) -> b -> a -> c #
flip ff.
>>>flip (++) "hello" "world""worldhello"
const x is a unary function which evaluates to x for all inputs.
>>>const 42 "hello"42
>>>map (const 42) [0..3][42,42,42,42]
liftM5 :: Monad m => (a1 -> a2 -> a3 -> a4 -> a5 -> r) -> m a1 -> m a2 -> m a3 -> m a4 -> m a5 -> m r #
Promote a function to a monad, scanning the monadic arguments from
left to right (cf. liftM2).
liftM4 :: Monad m => (a1 -> a2 -> a3 -> a4 -> r) -> m a1 -> m a2 -> m a3 -> m a4 -> m r #
Promote a function to a monad, scanning the monadic arguments from
left to right (cf. liftM2).
liftM3 :: Monad m => (a1 -> a2 -> a3 -> r) -> m a1 -> m a2 -> m a3 -> m r #
Promote a function to a monad, scanning the monadic arguments from
left to right (cf. liftM2).
liftM2 :: Monad m => (a1 -> a2 -> r) -> m a1 -> m a2 -> m r #
Promote a function to a monad, scanning the monadic arguments from left to right. For example,
liftM2 (+) [0,1] [0,2] = [0,2,1,3] liftM2 (+) (Just 1) Nothing = Nothing
when :: Applicative f => Bool -> f () -> f () #
Conditional execution of Applicative expressions. For example,
when debug (putStrLn "Debugging")
will output the string Debugging if the Boolean value debug
is True, and otherwise do nothing.
(=<<) :: Monad m => (a -> m b) -> m a -> m b infixr 1 #
Same as >>=, but with the arguments interchanged.
(<|>) :: Alternative f => f a -> f a -> f a infixl 3 #
An associative binary operation
class (Alternative m, Monad m) => MonadPlus (m :: * -> *) where #
Monads that also support choice and failure.
Methods
The identity of mplus. It should also satisfy the equations
mzero >>= f = mzero v >> mzero = mzero
The default definition is
mzero = empty
An associative operation. The default definition is
mplus = (<|>)
Instances
| MonadPlus [] | Since: base-2.1 |
| MonadPlus Maybe | Since: base-2.1 |
| MonadPlus IO | Since: base-4.9.0.0 |
| MonadPlus Option | Since: base-4.9.0.0 |
| MonadPlus ReadP | Since: base-2.1 |
| MonadPlus Vector | |
| MonadPlus Seq | |
| MonadPlus SmallArray | |
Defined in Data.Primitive.SmallArray | |
| MonadPlus Array | |
| MonadPlus P | Since: base-2.1 |
Defined in Text.ParserCombinators.ReadP | |
| MonadPlus (U1 :: * -> *) | Since: base-4.9.0.0 |
| (ArrowApply a, ArrowPlus a) => MonadPlus (ArrowMonad a) | Since: base-4.6.0.0 |
Defined in Control.Arrow | |
| MonadPlus f => MonadPlus (Rec1 f) | Since: base-4.9.0.0 |
| (Monad m, Error e) => MonadPlus (ErrorT e m) | |
| (MonadPlus f, MonadPlus g) => MonadPlus (f :*: g) | Since: base-4.9.0.0 |
| (MonadPlus f, MonadPlus g) => MonadPlus (Product f g) | Since: base-4.9.0.0 |
| MonadPlus f => MonadPlus (M1 i c f) | Since: base-4.9.0.0 |
undefined :: HasCallStack => a #
error :: HasCallStack => [Char] -> a #
error stops execution and displays an error message.
data SomeException #
The SomeException type is the root of the exception type hierarchy.
When an exception of type e is thrown, behind the scenes it is
encapsulated in a SomeException.
Instances
| Show SomeException | Since: base-3.0 |
Defined in GHC.Exception Methods showsPrec :: Int -> SomeException -> ShowS # show :: SomeException -> String # showList :: [SomeException] -> ShowS # | |
| Exception SomeException | Since: base-3.0 |
Defined in GHC.Exception Methods toException :: SomeException -> SomeException # fromException :: SomeException -> Maybe SomeException # displayException :: SomeException -> String # | |
getContents :: MonadIO m => m LText #
Since: basic-prelude-0.7.0
decodeUtf8 :: ByteString -> Text #
Note that this is not the standard Data.Text.Encoding.decodeUtf8. That
function will throw impure exceptions on any decoding errors. This function
instead uses decodeLenient.
fpToString :: FilePath -> String #
Since 0.3.13
fpFromText :: Text -> FilePath #
Since 0.3.13
fpToText :: FilePath -> Text #
This function assumes file paths are encoded in UTF8. If it
cannot decode the FilePath, the result is just an approximation.
Since 0.3.13
ltextToString :: LText -> String #
textToString :: Text -> String #
appendFile :: MonadIO m => FilePath -> Text -> m () #
Write Text to the end of a file.
Since: basic-prelude-0.7.0
writeFile :: MonadIO m => FilePath -> Text -> m () #
Write Text to a file. The file is truncated to zero length before writing begins.
Since: basic-prelude-0.7.0
readFile :: MonadIO m => FilePath -> m Text #
Read a file and return the contents of the file as Text. The entire file is read strictly.
Since: basic-prelude-0.7.0
readIO :: (MonadIO m, Read a) => Text -> m a #
The readIO function is similar to read except that it signals parse failure to the IO monad instead of terminating the program.
Since: basic-prelude-0.7.0
intercalate :: Monoid w => w -> [w] -> w #
intercalate = mconcat .: intersperse
terror :: HasCallStack => Text -> a #
error applied to Text
Since 0.4.1
type LByteString = ByteString #
Boxed vectors, supporting efficient slicing.
Instances
| Monad Vector | |
| Functor Vector | |
| Applicative Vector | |
| Foldable Vector | |
Defined in Data.Vector Methods fold :: Monoid m => Vector m -> m # foldMap :: Monoid m => (a -> m) -> Vector a -> m # foldr :: (a -> b -> b) -> b -> Vector a -> b # foldr' :: (a -> b -> b) -> b -> Vector a -> b # foldl :: (b -> a -> b) -> b -> Vector a -> b # foldl' :: (b -> a -> b) -> b -> Vector a -> b # foldr1 :: (a -> a -> a) -> Vector a -> a # foldl1 :: (a -> a -> a) -> Vector a -> a # elem :: Eq a => a -> Vector a -> Bool # maximum :: Ord a => Vector a -> a # minimum :: Ord a => Vector a -> a # | |
| Traversable Vector | |
| Eq1 Vector | |
| Ord1 Vector | |
Defined in Data.Vector | |
| Read1 Vector | |
Defined in Data.Vector | |
| Show1 Vector | |
| MonadZip Vector | |
| Alternative Vector | |
| MonadPlus Vector | |
| Vector Vector a | |
Defined in Data.Vector Methods basicUnsafeFreeze :: PrimMonad m => Mutable Vector (PrimState m) a -> m (Vector a) # basicUnsafeThaw :: PrimMonad m => Vector a -> m (Mutable Vector (PrimState m) a) # basicLength :: Vector a -> Int # basicUnsafeSlice :: Int -> Int -> Vector a -> Vector a # basicUnsafeIndexM :: Monad m => Vector a -> Int -> m a # basicUnsafeCopy :: PrimMonad m => Mutable Vector (PrimState m) a -> Vector a -> m () # | |
| IsList (Vector a) | |
| Eq a => Eq (Vector a) | |
| Data a => Data (Vector a) | |
Defined in Data.Vector Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Vector a -> c (Vector a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Vector a) # toConstr :: Vector a -> Constr # dataTypeOf :: Vector a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Vector a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Vector a)) # gmapT :: (forall b. Data b => b -> b) -> Vector a -> Vector a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Vector a -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Vector a -> r # gmapQ :: (forall d. Data d => d -> u) -> Vector a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Vector a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Vector a -> m (Vector a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Vector a -> m (Vector a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Vector a -> m (Vector a) # | |
| Ord a => Ord (Vector a) | |
Defined in Data.Vector | |
| Read a => Read (Vector a) | |
| Show a => Show (Vector a) | |
| Semigroup (Vector a) | |
| Monoid (Vector a) | |
| NFData a => NFData (Vector a) | |
Defined in Data.Vector | |
| type Mutable Vector | |
Defined in Data.Vector | |
| type Item (Vector a) | |
Defined in Data.Vector | |
class (Vector Vector a, MVector MVector a) => Unbox a #
Instances
A map from keys to values. A map cannot contain duplicate keys; each key can map to at most one value.
Instances
| Eq2 HashMap | |
| Ord2 HashMap | |
Defined in Data.HashMap.Base | |
| Show2 HashMap | |
| Hashable2 HashMap | |
Defined in Data.HashMap.Base | |
| Functor (HashMap k) | |
| Foldable (HashMap k) | |
Defined in Data.HashMap.Base Methods fold :: Monoid m => HashMap k m -> m # foldMap :: Monoid m => (a -> m) -> HashMap k a -> m # foldr :: (a -> b -> b) -> b -> HashMap k a -> b # foldr' :: (a -> b -> b) -> b -> HashMap k a -> b # foldl :: (b -> a -> b) -> b -> HashMap k a -> b # foldl' :: (b -> a -> b) -> b -> HashMap k a -> b # foldr1 :: (a -> a -> a) -> HashMap k a -> a # foldl1 :: (a -> a -> a) -> HashMap k a -> a # toList :: HashMap k a -> [a] # length :: HashMap k a -> Int # elem :: Eq a => a -> HashMap k a -> Bool # maximum :: Ord a => HashMap k a -> a # minimum :: Ord a => HashMap k a -> a # | |
| Traversable (HashMap k) | |
Defined in Data.HashMap.Base | |
| Eq k => Eq1 (HashMap k) | |
| Ord k => Ord1 (HashMap k) | |
Defined in Data.HashMap.Base | |
| (Eq k, Hashable k, Read k) => Read1 (HashMap k) | |
Defined in Data.HashMap.Base | |
| Show k => Show1 (HashMap k) | |
| Hashable k => Hashable1 (HashMap k) | |
Defined in Data.HashMap.Base | |
| (Eq k, Hashable k) => IsList (HashMap k v) | |
| (Eq k, Eq v) => Eq (HashMap k v) | |
| (Data k, Data v, Eq k, Hashable k) => Data (HashMap k v) | |
Defined in Data.HashMap.Base Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HashMap k v -> c (HashMap k v) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (HashMap k v) # toConstr :: HashMap k v -> Constr # dataTypeOf :: HashMap k v -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (HashMap k v)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (HashMap k v)) # gmapT :: (forall b. Data b => b -> b) -> HashMap k v -> HashMap k v # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HashMap k v -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HashMap k v -> r # gmapQ :: (forall d. Data d => d -> u) -> HashMap k v -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> HashMap k v -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> HashMap k v -> m (HashMap k v) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> HashMap k v -> m (HashMap k v) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> HashMap k v -> m (HashMap k v) # | |
| (Ord k, Ord v) => Ord (HashMap k v) | The order is total. Note: Because the hash is not guaranteed to be stable across library
versions, OSes, or architectures, neither is an actual order of elements in
|
Defined in Data.HashMap.Base | |
| (Eq k, Hashable k, Read k, Read e) => Read (HashMap k e) | |
| (Show k, Show v) => Show (HashMap k v) | |
| (Eq k, Hashable k) => Semigroup (HashMap k v) | |
| (Eq k, Hashable k) => Monoid (HashMap k v) | |
| (Hashable k, Hashable v) => Hashable (HashMap k v) | |
Defined in Data.HashMap.Base | |
| (NFData k, NFData v) => NFData (HashMap k v) | |
Defined in Data.HashMap.Base | |
| type Item (HashMap k v) | |
Defined in Data.HashMap.Base | |
A set of values. A set cannot contain duplicate values.
Instances
| Foldable HashSet | |
Defined in Data.HashSet Methods fold :: Monoid m => HashSet m -> m # foldMap :: Monoid m => (a -> m) -> HashSet a -> m # foldr :: (a -> b -> b) -> b -> HashSet a -> b # foldr' :: (a -> b -> b) -> b -> HashSet a -> b # foldl :: (b -> a -> b) -> b -> HashSet a -> b # foldl' :: (b -> a -> b) -> b -> HashSet a -> b # foldr1 :: (a -> a -> a) -> HashSet a -> a # foldl1 :: (a -> a -> a) -> HashSet a -> a # elem :: Eq a => a -> HashSet a -> Bool # maximum :: Ord a => HashSet a -> a # minimum :: Ord a => HashSet a -> a # | |
| Eq1 HashSet | |
| Ord1 HashSet | |
Defined in Data.HashSet | |
| Show1 HashSet | |
| Hashable1 HashSet | |
Defined in Data.HashSet | |
| (Eq a, Hashable a) => IsList (HashSet a) | |
| Eq a => Eq (HashSet a) | |
| (Data a, Eq a, Hashable a) => Data (HashSet a) | |
Defined in Data.HashSet Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HashSet a -> c (HashSet a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (HashSet a) # toConstr :: HashSet a -> Constr # dataTypeOf :: HashSet a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (HashSet a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (HashSet a)) # gmapT :: (forall b. Data b => b -> b) -> HashSet a -> HashSet a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HashSet a -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HashSet a -> r # gmapQ :: (forall d. Data d => d -> u) -> HashSet a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> HashSet a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> HashSet a -> m (HashSet a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> HashSet a -> m (HashSet a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> HashSet a -> m (HashSet a) # | |
| Ord a => Ord (HashSet a) | |
| (Eq a, Hashable a, Read a) => Read (HashSet a) | |
| Show a => Show (HashSet a) | |
| (Hashable a, Eq a) => Semigroup (HashSet a) | |
| (Hashable a, Eq a) => Monoid (HashSet a) | |
| Hashable a => Hashable (HashSet a) | |
Defined in Data.HashSet | |
| NFData a => NFData (HashSet a) | |
Defined in Data.HashSet | |
| type Item (HashSet a) | |
Defined in Data.HashSet | |
A space efficient, packed, unboxed Unicode text type.
encodeUtf8 :: Text -> ByteString #
Encode text using UTF-8 encoding.
The class of types that can be converted to a hash value.
Minimal implementation: hashWithSalt.
Methods
hashWithSalt :: Int -> a -> Int infixl 0 #
Return a hash value for the argument, using the given salt.
The general contract of hashWithSalt is:
- If two values are equal according to the
==method, then applying thehashWithSaltmethod on each of the two values must produce the same integer result if the same salt is used in each case. - It is not required that if two values are unequal
according to the
==method, then applying thehashWithSaltmethod on each of the two values must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal values may improve the performance of hashing-based data structures. - This method can be used to compute different hash values for
the same input by providing a different salt in each
application of the method. This implies that any instance
that defines
hashWithSaltmust make use of the salt in its implementation.
Like hashWithSalt, but no salt is used. The default
implementation uses hashWithSalt with some default salt.
Instances might want to implement this method to provide a more
efficient implementation than the default implementation.
Instances
(<.>) :: FilePath -> String -> FilePath infixr 7 #
Add an extension, even if there is already one there, equivalent to addExtension.
"/directory/path" <.> "ext" == "/directory/path.ext" "/directory/path" <.> ".ext" == "/directory/path.ext"
(</>) :: FilePath -> FilePath -> FilePath infixr 5 #
Combine two paths with a path separator.
If the second path starts with a path separator or a drive letter, then it returns the second.
The intention is that readFile (dir will access the same file as
</> file)setCurrentDirectory dir; readFile file.
Posix: "/directory" </> "file.ext" == "/directory/file.ext"
Windows: "/directory" </> "file.ext" == "/directory\\file.ext"
"directory" </> "/file.ext" == "/file.ext"
Valid x => (takeDirectory x </> takeFileName x) `equalFilePath` xCombined:
Posix: "/" </> "test" == "/test" Posix: "home" </> "bob" == "home/bob" Posix: "x:" </> "foo" == "x:/foo" Windows: "C:\\foo" </> "bar" == "C:\\foo\\bar" Windows: "home" </> "bob" == "home\\bob"
Not combined:
Posix: "home" </> "/bob" == "/bob" Windows: "home" </> "C:\\bob" == "C:\\bob"
Not combined (tricky):
On Windows, if a filepath starts with a single slash, it is relative to the
root of the current drive. In [1], this is (confusingly) referred to as an
absolute path.
The current behavior of </> is to never combine these forms.
Windows: "home" </> "/bob" == "/bob" Windows: "home" </> "\\bob" == "\\bob" Windows: "C:\\home" </> "\\bob" == "\\bob"
On Windows, from [1]: "If a file name begins with only a disk designator
but not the backslash after the colon, it is interpreted as a relative path
to the current directory on the drive with the specified letter."
The current behavior of </> is to never combine these forms.
Windows: "D:\\foo" </> "C:bar" == "C:bar" Windows: "C:\\foo" </> "C:bar" == "C:bar"
A set of values a.
Instances
| Foldable Set | |
Defined in Data.Set.Internal Methods fold :: Monoid m => Set m -> m # foldMap :: Monoid m => (a -> m) -> Set a -> m # foldr :: (a -> b -> b) -> b -> Set a -> b # foldr' :: (a -> b -> b) -> b -> Set a -> b # foldl :: (b -> a -> b) -> b -> Set a -> b # foldl' :: (b -> a -> b) -> b -> Set a -> b # foldr1 :: (a -> a -> a) -> Set a -> a # foldl1 :: (a -> a -> a) -> Set a -> a # elem :: Eq a => a -> Set a -> Bool # maximum :: Ord a => Set a -> a # | |
| Eq1 Set | Since: containers-0.5.9 |
| Ord1 Set | Since: containers-0.5.9 |
Defined in Data.Set.Internal | |
| Show1 Set | Since: containers-0.5.9 |
| Ord a => IsList (Set a) | Since: containers-0.5.6.2 |
| Eq a => Eq (Set a) | |
| (Data a, Ord a) => Data (Set a) | |
Defined in Data.Set.Internal Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Set a -> c (Set a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Set a) # dataTypeOf :: Set a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Set a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Set a)) # gmapT :: (forall b. Data b => b -> b) -> Set a -> Set a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Set a -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Set a -> r # gmapQ :: (forall d. Data d => d -> u) -> Set a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Set a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Set a -> m (Set a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Set a -> m (Set a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Set a -> m (Set a) # | |
| Ord a => Ord (Set a) | |
| (Read a, Ord a) => Read (Set a) | |
| Show a => Show (Set a) | |
| Ord a => Semigroup (Set a) | Since: containers-0.5.7 |
| Ord a => Monoid (Set a) | |
| NFData a => NFData (Set a) | |
Defined in Data.Set.Internal | |
| type Item (Set a) | |
Defined in Data.Set.Internal | |
General-purpose finite sequences.
Instances
| Monad Seq | |
| Functor Seq | |
| MonadFix Seq | Since: containers-0.5.11 |
Defined in Data.Sequence.Internal | |
| Applicative Seq | Since: containers-0.5.4 |
| Foldable Seq | |
Defined in Data.Sequence.Internal Methods fold :: Monoid m => Seq m -> m # foldMap :: Monoid m => (a -> m) -> Seq a -> m # foldr :: (a -> b -> b) -> b -> Seq a -> b # foldr' :: (a -> b -> b) -> b -> Seq a -> b # foldl :: (b -> a -> b) -> b -> Seq a -> b # foldl' :: (b -> a -> b) -> b -> Seq a -> b # foldr1 :: (a -> a -> a) -> Seq a -> a # foldl1 :: (a -> a -> a) -> Seq a -> a # elem :: Eq a => a -> Seq a -> Bool # maximum :: Ord a => Seq a -> a # | |
| Traversable Seq | |
| Eq1 Seq | Since: containers-0.5.9 |
| Ord1 Seq | Since: containers-0.5.9 |
Defined in Data.Sequence.Internal | |
| Read1 Seq | Since: containers-0.5.9 |
Defined in Data.Sequence.Internal | |
| Show1 Seq | Since: containers-0.5.9 |
| MonadZip Seq |
|
| Alternative Seq | Since: containers-0.5.4 |
| MonadPlus Seq | |
| UnzipWith Seq | |
Defined in Data.Sequence.Internal Methods unzipWith' :: (x -> (a, b)) -> Seq x -> (Seq a, Seq b) | |
| IsList (Seq a) | |
| Eq a => Eq (Seq a) | |
| Data a => Data (Seq a) | |
Defined in Data.Sequence.Internal Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Seq a -> c (Seq a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Seq a) # dataTypeOf :: Seq a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Seq a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Seq a)) # gmapT :: (forall b. Data b => b -> b) -> Seq a -> Seq a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Seq a -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Seq a -> r # gmapQ :: (forall d. Data d => d -> u) -> Seq a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Seq a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Seq a -> m (Seq a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Seq a -> m (Seq a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Seq a -> m (Seq a) # | |
| Ord a => Ord (Seq a) | |
| Read a => Read (Seq a) | |
| Show a => Show (Seq a) | |
| a ~ Char => IsString (Seq a) | Since: containers-0.5.7 |
Defined in Data.Sequence.Internal Methods fromString :: String -> Seq a # | |
| Semigroup (Seq a) | Since: containers-0.5.7 |
| Monoid (Seq a) | |
| NFData a => NFData (Seq a) | |
Defined in Data.Sequence.Internal | |
| type Item (Seq a) | |
Defined in Data.Sequence.Internal | |
A Map from keys k to values a.
Instances
| Eq2 Map | Since: containers-0.5.9 |
| Ord2 Map | Since: containers-0.5.9 |
Defined in Data.Map.Internal | |
| Show2 Map | Since: containers-0.5.9 |
| Functor (Map k) | |
| Foldable (Map k) | |
Defined in Data.Map.Internal Methods fold :: Monoid m => Map k m -> m # foldMap :: Monoid m => (a -> m) -> Map k a -> m # foldr :: (a -> b -> b) -> b -> Map k a -> b # foldr' :: (a -> b -> b) -> b -> Map k a -> b # foldl :: (b -> a -> b) -> b -> Map k a -> b # foldl' :: (b -> a -> b) -> b -> Map k a -> b # foldr1 :: (a -> a -> a) -> Map k a -> a # foldl1 :: (a -> a -> a) -> Map k a -> a # elem :: Eq a => a -> Map k a -> Bool # maximum :: Ord a => Map k a -> a # minimum :: Ord a => Map k a -> a # | |
| Traversable (Map k) | |
| Eq k => Eq1 (Map k) | Since: containers-0.5.9 |
| Ord k => Ord1 (Map k) | Since: containers-0.5.9 |
Defined in Data.Map.Internal | |
| (Ord k, Read k) => Read1 (Map k) | Since: containers-0.5.9 |
Defined in Data.Map.Internal | |
| Show k => Show1 (Map k) | Since: containers-0.5.9 |
| Ord k => IsList (Map k v) | Since: containers-0.5.6.2 |
| (Eq k, Eq a) => Eq (Map k a) | |
| (Data k, Data a, Ord k) => Data (Map k a) | |
Defined in Data.Map.Internal Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Map k a -> c (Map k a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Map k a) # toConstr :: Map k a -> Constr # dataTypeOf :: Map k a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Map k a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Map k a)) # gmapT :: (forall b. Data b => b -> b) -> Map k a -> Map k a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Map k a -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Map k a -> r # gmapQ :: (forall d. Data d => d -> u) -> Map k a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Map k a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Map k a -> m (Map k a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Map k a -> m (Map k a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Map k a -> m (Map k a) # | |
| (Ord k, Ord v) => Ord (Map k v) | |
| (Ord k, Read k, Read e) => Read (Map k e) | |
| (Show k, Show a) => Show (Map k a) | |
| Ord k => Semigroup (Map k v) | |
| Ord k => Monoid (Map k v) | |
| (NFData k, NFData a) => NFData (Map k a) | |
Defined in Data.Map.Internal | |
| type Item (Map k v) | |
Defined in Data.Map.Internal | |
A set of integers.
Instances
| IsList IntSet | Since: containers-0.5.6.2 |
| Eq IntSet | |
| Data IntSet | |
Defined in Data.IntSet.Internal Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> IntSet -> c IntSet # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c IntSet # toConstr :: IntSet -> Constr # dataTypeOf :: IntSet -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c IntSet) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c IntSet) # gmapT :: (forall b. Data b => b -> b) -> IntSet -> IntSet # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> IntSet -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> IntSet -> r # gmapQ :: (forall d. Data d => d -> u) -> IntSet -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> IntSet -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> IntSet -> m IntSet # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> IntSet -> m IntSet # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> IntSet -> m IntSet # | |
| Ord IntSet | |
| Read IntSet | |
| Show IntSet | |
| Semigroup IntSet | Since: containers-0.5.7 |
| Monoid IntSet | |
| NFData IntSet | |
Defined in Data.IntSet.Internal | |
| type Item IntSet | |
Defined in Data.IntSet.Internal | |
A map of integers to values a.
Instances
| Functor IntMap | |
| Foldable IntMap | |
Defined in Data.IntMap.Internal Methods fold :: Monoid m => IntMap m -> m # foldMap :: Monoid m => (a -> m) -> IntMap a -> m # foldr :: (a -> b -> b) -> b -> IntMap a -> b # foldr' :: (a -> b -> b) -> b -> IntMap a -> b # foldl :: (b -> a -> b) -> b -> IntMap a -> b # foldl' :: (b -> a -> b) -> b -> IntMap a -> b # foldr1 :: (a -> a -> a) -> IntMap a -> a # foldl1 :: (a -> a -> a) -> IntMap a -> a # elem :: Eq a => a -> IntMap a -> Bool # maximum :: Ord a => IntMap a -> a # minimum :: Ord a => IntMap a -> a # | |
| Traversable IntMap | |
| Eq1 IntMap | Since: containers-0.5.9 |
| Ord1 IntMap | Since: containers-0.5.9 |
Defined in Data.IntMap.Internal | |
| Read1 IntMap | Since: containers-0.5.9 |
Defined in Data.IntMap.Internal | |
| Show1 IntMap | Since: containers-0.5.9 |
| IsList (IntMap a) | Since: containers-0.5.6.2 |
| Eq a => Eq (IntMap a) | |
| Data a => Data (IntMap a) | |
Defined in Data.IntMap.Internal Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> IntMap a -> c (IntMap a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (IntMap a) # toConstr :: IntMap a -> Constr # dataTypeOf :: IntMap a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (IntMap a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (IntMap a)) # gmapT :: (forall b. Data b => b -> b) -> IntMap a -> IntMap a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> IntMap a -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> IntMap a -> r # gmapQ :: (forall d. Data d => d -> u) -> IntMap a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> IntMap a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> IntMap a -> m (IntMap a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> IntMap a -> m (IntMap a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> IntMap a -> m (IntMap a) # | |
| Ord a => Ord (IntMap a) | |
Defined in Data.IntMap.Internal | |
| Read e => Read (IntMap e) | |
| Show a => Show (IntMap a) | |
| Semigroup (IntMap a) | Since: containers-0.5.7 |
| Monoid (IntMap a) | |
| NFData a => NFData (IntMap a) | |
Defined in Data.IntMap.Internal | |
| type Item (IntMap a) | |
Defined in Data.IntMap.Internal | |
data ByteString #
A space-efficient representation of a Word8 vector, supporting many
efficient operations.
A ByteString contains 8-bit bytes, or by using the operations from
Data.ByteString.Char8 it can be interpreted as containing 8-bit
characters.
Instances
The identity function which requires the inner argument to be (). Useful for functions
with overloaded return types.
\(x :: Maybe ()) -> unit x == x
lift :: (MonadTrans t, Monad m) => m a -> t m a #
Lift a computation from the argument monad to the constructed monad.
askOracleWith :: (RuleResult q ~ a, ShakeValue q, ShakeValue a) => q -> a -> Action a #
Depreciated: Replace askOracleWith q aaskOracle qRuleResult type family now fixes the result type.
(*>) :: FilePattern -> (FilePath -> Action ()) -> Rules () infix 1 #
Deprecated: Alias for %>. Note that *> clashes with a Prelude operator in GHC 7.10.
(?>>) :: (FilePath -> Maybe [FilePath]) -> ([FilePath] -> Action ()) -> Rules () infix 1 #
Deprecated: Alias for &?>.
shakeOptDescrs :: [OptDescr (Either String (ShakeOptions -> ShakeOptions))] #
A list of command line options that can be used to modify ShakeOptions. Each option returns
either an error message (invalid argument to the flag) or a function that changes some fields
in ShakeOptions. The command line flags are make compatible where possbile, but additional
flags have been added for the extra options Shake supports.
shakeArgsOptionsWith :: ShakeOptions -> [OptDescr (Either String a)] -> (ShakeOptions -> [a] -> [String] -> IO (Maybe (ShakeOptions, Rules ()))) -> IO () #
Like shakeArgsWith, but also lets you manipulate the ShakeOptions.
shakeArgsWith :: ShakeOptions -> [OptDescr (Either String a)] -> ([a] -> [String] -> IO (Maybe (Rules ()))) -> IO () #
A version of shakeArgs with more flexible handling of command line arguments.
The caller of shakeArgsWith can add additional flags (the second argument) and chose how to convert
the flags/arguments into rules (the third argument). Given:
shakeArgsWith opts flags (\flagValues argValues -> result)
optsis the initialShakeOptionsvalue, which may have some fields overriden by command line flags. This argument is usuallyshakeOptions, perhaps with a few fields overriden.flagsis a list of flag descriptions, which either produce aStringcontaining an error message (typically for flags with invalid arguments, .e.g.Left"could not parse as int"flagValues. If you have no custom flags, pass[].flagValuesis a list of custom flags that the user supplied. Ifflags == []then this list will be[].argValuesis a list of non-flag arguments, which are often treated as files and passed towant.resultshould produce aNothingto indicate that no building needs to take place, or aJustproviding the rules that should be used.
As an example of a build system that can use either gcc or distcc for compiling:
import System.Console.GetOpt data Flags = DistCC deriving Eq flags = [Option "" ["distcc"] (NoArg $ Right DistCC) "Run distributed."] main =shakeArgsWithshakeOptionsflags $ \flags targets -> return $ Just $ do if null targets thenwant["result.exe"] elsewanttargets let compiler = if DistCC `elem` flags then "distcc" else "gcc" "*.o"%>\out -> doneed...cmdcompiler ... ...
Now you can pass --distcc to use the distcc compiler.
shakeArgs :: ShakeOptions -> Rules () -> IO () #
Run a build system using command line arguments for configuration.
The available flags are those from shakeOptDescrs, along with a few additional
make compatible flags that are not represented in ShakeOptions, such as --print-directory.
If there are no file arguments then the Rules are used directly, otherwise the file arguments
are wanted (after calling withoutActions). As an example:
main =shakeArgsshakeOptions{shakeFiles= "_make",shakeProgress=progressSimple} $ dophony"clean" $removeFilesAfter"_make" ["//*"]want["_make/neil.txt","_make/emily.txt"] "_make/*.txt"%>\out -> ... build action here ...
This build system will default to building neil.txt and emily.txt, while showing progress messages,
and putting the Shake files in locations such as _make/.database. Some example command line flags:
main --no-progresswill turn off progress messages.main -j6will build on 6 threads.main --helpwill display a list of supported flags.main cleanwill not build anything, but will remove the_makedirectory, including the anyshakeFiles.main _make/henry.txtwill not buildneil.txtoremily.txt, but will instead buildhenry.txt.
cmd_ :: (CmdArguments args, Unit args) => args :-> Action () #
cmd :: CmdArguments args => args :-> Action r #
Execute a system command. Before running cmd make sure you need any files
that are used by the command.
Stringarguments are treated as whitespace separated arguments.[String]arguments are treated as literal arguments.CmdOptionarguments are used as options.
As some examples, here are some calls, and the resulting command string:
cmd_"git log --pretty=" "oneline" -- git log --pretty= onelinecmd_"git log --pretty=" ["oneline"] -- git log --pretty= onelinecmd_"git log" ("--pretty=" ++ "oneline") -- git log --pretty=onelinecmd_"git log" ("--pretty=" ++ "one line") -- git log --pretty=one linecmd_"git log" ["--pretty=" ++ "one line"] -- git log "--pretty=one line"
More examples, including return values, see this translation of the examples given for the command function:
cmd_"gcc -c myfile.c" -- compile a file, throwing an exception on failureExitc <-cmd"gcc -c" [myfile] -- run a command, recording the exit code (Exitc,Stderrerr) <-cmd"gcc -c myfile.c" -- run a command, recording the exit code and error outputStdoutout <-cmd"gcc -MM myfile.c" -- run a command, recording the outputcmd(Cwd"generated") "gcc -c" [myfile] ::Action() -- run a command in a directory
When passing file arguments we use [myfile] so that if the myfile variable contains spaces they are properly escaped.
If you use cmd inside a do block and do not use the result, you may get a compile-time error about being
unable to deduce CmdResult. To avoid this error, use cmd_.
The cmd function can also be run in the IO monad, but then Traced is ignored and command lines are not echoed.
As an example:
cmd(Cwd"generated")Shell"gcc -c myfile.c" :: IO ()
command :: CmdResult r => [CmdOption] -> String -> [String] -> Action r #
Execute a system command. Before running command make sure you need any files
that are used by the command.
This function takes a list of options (often just [], see CmdOption for the available
options), the name of the executable (either a full name, or a program on the $PATH) and
a list of arguments. The result is often (), but can be a tuple containg any of Stdout,
Stderr and Exit. Some examples:
command_[] "gcc" ["-c","myfile.c"] -- compile a file, throwing an exception on failureExitc <-command[] "gcc" ["-c",myfile] -- run a command, recording the exit code (Exitc,Stderrerr) <-command[] "gcc" ["-c","myfile.c"] -- run a command, recording the exit code and error outputStdoutout <-command[] "gcc" ["-MM","myfile.c"] -- run a command, recording the outputcommand_[Cwd"generated"] "gcc" ["-c",myfile] -- run a command in a directory
Unless you retrieve the ExitCode using Exit, any ExitFailure will throw an error, including
the Stderr in the exception message. If you capture the Stdout or Stderr, that stream will not be echoed to the console,
unless you use the option EchoStdout or EchoStderr.
If you use command inside a do block and do not use the result, you may get a compile-time error about being
unable to deduce CmdResult. To avoid this error, use command_.
By default the stderr stream will be captured for use in error messages, and also echoed. To only echo
pass WithStderr Falsegcc)
to detect they are running in a terminal.
addEnv :: MonadIO m => [(String, String)] -> m CmdOption #
Deprecated: Use AddEnv. This function will be removed in a future version.
Add a single variable to the environment. For example:
opt <-addEnv[("CFLAGS","-O2")]cmdopt "gcc -c main.c"
Would add the environment variable $CFLAGS with value -O2. If the variable $CFLAGS
was already defined it would be overwritten. If you wish to modify $PATH see addPath.
addPath :: MonadIO m => [String] -> [String] -> m CmdOption #
Deprecated: Use AddPath. This function will be removed in a future version.
Add a prefix and suffix to the $PATH environment variable. For example:
opt <-addPath["/usr/special"] []cmdopt "userbinary --version"
Would prepend /usr/special to the current $PATH, and the command would pick
/usr/special/userbinary, if it exists. To add other variables see addEnv.
Collect the stdout of the process.
If used, the stdout will not be echoed to the terminal, unless you include EchoStdout.
The value type may be either String, or either lazy or strict ByteString.
Constructors
| Stdout | |
Fields
| |
Collect the stderr of the process.
If used, the stderr will not be echoed to the terminal, unless you include EchoStderr.
The value type may be either String, or either lazy or strict ByteString.
Constructors
| Stderr | |
Fields
| |
Collect the stdout and stderr of the process.
If used, the stderr and stdout will not be echoed to the terminal, unless you include EchoStdout and EchoStderr.
The value type may be either String, or either lazy or strict ByteString.
Constructors
| Stdouterr | |
Fields
| |
Collect the ExitCode of the process.
If you do not collect the exit code, any ExitFailure will cause an exception.
Instances
| CmdResult Exit | |
Defined in Development.Shake.Command | |
Collect the ProcessHandle of the process.
If you do collect the process handle, the command will run asyncronously and the call to cmd / command
will return as soon as the process is spawned. Any Stdout / Stderr captures will return empty strings.
Constructors
| Process | |
Fields | |
Instances
| CmdResult Process | |
Defined in Development.Shake.Command | |
Collect the time taken to execute the process. Can be used in conjunction with CmdLine to
write helper functions that print out the time of a result.
timer :: (CmdResultr, MonadIO m) => (forall r .CmdResultr => m r) -> m r timer act = do (CmdTimet,CmdLinex, r) <- act liftIO $ putStrLn $ "Command " ++ x ++ " took " ++ show t ++ " seconds" return r run :: IO () run = timer $cmd"ghc --version"
Constructors
| CmdTime | |
Fields | |
Instances
| CmdResult CmdTime | |
Defined in Development.Shake.Command | |
Collect the command line used for the process. This command line will be approximate - suitable for user diagnostics, but not for direct execution.
Constructors
| CmdLine | |
Fields | |
Instances
| CmdResult CmdLine | |
Defined in Development.Shake.Command | |
The allowable String-like values that can be captured.
Minimal complete definition
cmdString
Instances
| CmdString () | |
Defined in Development.Shake.Command Methods cmdString :: (Str, Str -> ()) | |
| CmdString String | |
Defined in Development.Shake.Command | |
| CmdString ByteString | |
Defined in Development.Shake.Command Methods cmdString :: (Str, Str -> ByteString) | |
| CmdString ByteString | |
Defined in Development.Shake.Command Methods cmdString :: (Str, Str -> ByteString) | |
A class for specifying what results you want to collect from a process.
Values are formed of Stdout, Stderr, Exit and tuples of those.
Minimal complete definition
cmdResult
Instances
newCache :: (Eq k, Hashable k) => (k -> Action v) -> Rules (k -> Action v) #
Given an action on a key, produce a cached version that will execute the action at most once per key per run.
Using the cached result will still result include any dependencies that the action requires.
Each call to newCache creates a separate cache that is independent of all other calls to newCache.
The operations will not be cached between runs and nothing will be persisted to the Shake database.
This function is useful when creating files that store intermediate values, to avoid the overhead of repeatedly reading from disk, particularly if the file requires expensive parsing. As an example:
digits <-newCache$ \file -> do src <- readFile' file return $ length $ filter isDigit src "*.digits"%>\x -> do v1 <- digits (dropExtensionx) v2 <- digits (dropExtensionx)writeFile'x $ show (v1,v2)
To create the result MyFile.txt.digits the file MyFile.txt will be read and counted, but only at most
once per execution.
withResources :: [(Resource, Int)] -> Action a -> Action a #
Run an action which uses part of several finite resources. Acquires the resources in a stable
order, to prevent deadlock. If all rules requiring more than one resource acquire those
resources with a single call to withResources, resources will not deadlock.
newThrottle :: String -> Int -> Double -> Rules Resource #
Create a throttled resource, given a name (for error messages) and a number of resources (the Int) that can be
used per time period (the Double in seconds). Shake will ensure that actions using the same throttled resource
do not exceed the limits. As an example, let us assume that making more than 1 request every 5 seconds to
Google results in our client being blacklisted, we can write:
google <-newThrottle"Google" 1 5 "*.url"%>\out -> dowithResourcegoogle 1 $cmd"wget" ["https://google.com?q=" ++takeBaseNameout] "-O" [out]
Now we will wait at least 5 seconds after querying Google before performing another query. If Google change the rules to
allow 12 requests per minute we can instead use newThrottle "Google" 12 60
In the original example we never make a fresh request until 5 seconds after the previous request has completed. If we instead want to throttle requests since the previous request started we can write:
google <-newThrottle"Google" 1 5 "*.url"%>\out -> dowithResourcegoogle 1 $ return ()cmd"wget" ["https://google.com?q=" ++takeBaseNameout] "-O" [out]
However, the rule may not continue running immediately after withResource completes, so while
we will never exceed an average of 1 request every 5 seconds, we may end up running an unbounded number of
requests simultaneously. If this limitation causes a problem in practice it can be fixed.
newResource :: String -> Int -> Rules Resource #
Create a finite resource, given a name (for error messages) and a quantity of the resource that exists. Shake will ensure that actions using the same finite resource do not execute in parallel. As an example, only one set of calls to the Excel API can occur at one time, therefore Excel is a finite resource of quantity 1. You can write:
shakeshakeOptions{shakeThreads=2} $ dowant["a.xls","b.xls"] excel <-newResource"Excel" 1 "*.xls"%>\out ->withResourceexcel 1 $cmd"excel" out ...
Now the two calls to excel will not happen in parallel.
As another example, calls to compilers are usually CPU bound but calls to linkers are usually disk bound. Running 8 linkers will often cause an 8 CPU system to grid to a halt. We can limit ourselves to 4 linkers with:
disk <-newResource"Disk" 4want[show i<.>"exe" | i <- [1..100]] "*.exe"%>\out ->withResourcedisk 1 $cmd"ld -o" [out] ... "*.o"%>\out ->cmd"cl -o" [out] ...
par :: Action a -> Action b -> Action (a, b) #
Execute two operations in parallel, based on parallel.
withTempDirWithin :: FilePath -> (FilePath -> Action a) -> Action a #
Like withTempDir but using a custom temporary directory.
withTempDir :: (FilePath -> Action a) -> Action a #
Create a temporary directory inside the system temporary directory. The directory will be deleted after the action completes. As an example:
withTempDir$ \mydir -> doputNormal$ "Temp directory is " ++ mydirwriteFile'(mydir </> "test.txt") "writing out a temp file"
withTempFileWithin :: FilePath -> (FilePath -> Action a) -> Action a #
Like withTempFile but using a custom temporary directory.
withTempFile :: (FilePath -> Action a) -> Action a #
Create a temporary file in the temporary directory. The file will be deleted
after the action completes (provided the file is not still open).
The FilePath will not have any file extension, will exist, and will be zero bytes long.
If you require a file with a specific name, use withTempDir.
writeFileChanged :: MonadIO m => FilePath -> String -> m () #
Write a file, but only if the contents would change.
writeFileLines :: MonadIO m => FilePath -> [String] -> m () #
A version of writeFile' which writes out a list of lines.
readFileLines :: FilePath -> Action [String] #
A version of readFile' which also splits the result into lines.
The argument file will be tracked as a dependency.
readFile' :: FilePath -> Action String #
Read a file, after calling need. The argument file will be tracked as a dependency.
copyFileChanged :: FilePath -> FilePath -> Action () #
copyFileChanged old new copies the existing file from old to new, if the contents have changed.
The old file will be tracked as a dependency.
Also creates the new directory if necessary.
copyFile' :: FilePath -> FilePath -> Action () #
copyFile' old new copies the existing file from old to new.
The old file will be tracked as a dependency.
Also creates the new directory if necessary.
addShakeExtra :: Typeable a => a -> HashMap TypeRep Dynamic -> HashMap TypeRep Dynamic #
Add a properly structued value to shakeExtra which can be retrieved with getShakeExtra.
getShakeExtraRules :: Typeable a => Rules (Maybe a) #
A version of getShakeExtra in Rules.
getShakeExtra :: Typeable a => Action (Maybe a) #
Get an item from shakeExtra, using the requested type as the key. Fails
if the value found at this key does not match the requested type.
getHashedShakeVersion :: [FilePath] -> IO String #
Get a checksum of a list of files, suitable for using as shakeVersion.
This will trigger a rebuild when the Shake rules defined in any of the files are changed.
For example:
main = do
ver <- getHashedShakeVersion ["Shakefile.hs"]
shakeArgs shakeOptions{shakeVersion = ver} ...
To automatically detect the name of the current file, turn on the TemplateHaskell
extension and write $(LitE . StringL . loc_filename <$> location).
This feature can be turned off during development by passing
the flag --no-rule-version or setting shakeVersionIgnore to True.
shake :: ShakeOptions -> Rules () -> IO () #
Main entry point for running Shake build systems. For an example see the top of the module Development.Shake.
Use ShakeOptions to specify how the system runs, and Rules to specify what to build. The function will throw
an exception if the build fails.
To use command line flags to modify ShakeOptions see shakeArgs.
removeFilesAfter :: FilePath -> [FilePattern] -> Action () #
Remove files, like removeFiles, but executed after the build completes successfully.
Useful for implementing clean actions that delete files Shake may have open for building.
removeFiles :: FilePath -> [FilePattern] -> IO () #
Remove all files and directories that match any of the patterns within a directory. Some examples:
removeFiles"output" ["//*"] -- delete everything inside 'output'removeFiles"output" ["//"] -- delete 'output' itselfremoveFiles"." ["//*.hi","//*.o"] -- delete all '.hi' and '.o' files
If the argument directory is missing no error is raised. This function will follow symlinks, so should be used with care.
This function is often useful when writing a clean action for your build system,
often as a phony rule.
getDirectoryFilesIO :: FilePath -> [FilePattern] -> IO [FilePath] #
A version of getDirectoryFiles that is in IO, and thus untracked.
getDirectoryDirs :: FilePath -> Action [FilePath] #
Get the directories in a directory, not including . or ...
All directories are relative to the argument directory.
The result itself is tracked as a dependency, but the directories in the result are not.
If the list of directories changes in subsequent builds any rule calling it will rerun.
getDirectoryFiles :: FilePath -> [FilePattern] -> Action [FilePath] #
Get the files anywhere under a directory that match any of a set of patterns.
For the interpretation of the patterns see ?==. All results will be
relative to the directory argument.
The result itself is tracked as a dependency, but the files in the result are not.
If the list of files changes in subsequent builds any rule calling it will rerun.
Some examples:
getDirectoryFiles "Config" ["//*.xml"]
-- All .xml files anywhere under the Config directory
-- If Config/foo/bar.xml exists it will return ["foo/bar.xml"]
getDirectoryFiles "Modules" ["*.hs","*.lhs"]
-- All .hs or .lhs in the Modules directory
-- If Modules/foo.hs and Modules/foo.lhs exist, it will return ["foo.hs","foo.lhs"]If you require a qualified file name it is often easier to use "" as the FilePath argument,
for example the following two expressions are equivalent:
fmap (map ("Config" </>)) (getDirectoryFiles "Config" ["//*.xml"])
getDirectoryFiles "" ["Config//*.xml"]If the first argument directory does not exist it will raise an error.
If foo does not exist, then the first of these error, but the second will not.
getDirectoryFiles "foo" ["//*"] -- error getDirectoryFiles "" ["foo//*"] -- returns []
This function is tracked and serves as a dependency. If a rule calls
getDirectoryFiles "" ["*.c"] and someone adds foo.c to the
directory, that rule will rebuild. If someone changes one of the .c files,
but the list of .c files doesn't change, then it will not rebuild.
As a consequence of being tracked, if the contents change during the build
(e.g. you are generating .c files in this directory) then the build not reach
a stable point, which is an error - detected by running with --lint.
You should normally only call this function returning source files.
For an untracked variant see getDirectoryFilesIO.
getDirectoryContents :: FilePath -> Action [FilePath] #
Get the contents of a directory. The result will be sorted, and will not contain
the entries . or .. (unlike the standard Haskell version).
The resulting paths will be relative to the first argument.
The result itself is tracked as a dependency, but the files in the result are not.
If the list of files changes in subsequent builds any rule calling it will rerun.
It is usually simpler to call either getDirectoryFiles or getDirectoryDirs.
getEnvWithDefault :: String -> String -> Action String #
getEnvWithDefault def varvar, or the
default value def if it is not set. Similar to getEnv.
flags <- getEnvWithDefault "-Wall" "CFLAGS"
cmd "gcc -c" [out] flags
getEnv :: String -> Action (Maybe String) #
Return Just the value of the environment variable, or Nothing
if the variable is not set. The environment variable is tracked as a
dependency, and if it changes the rule will rerun in subsequent builds.
This function is a tracked version of getEnv / lookupEnv from the base library.
flags <- getEnv "CFLAGS"
cmd "gcc -c" [out] (maybe [] words flags)
doesDirectoryExist :: FilePath -> Action Bool #
Returns True if the directory exists. The existence of the directory is tracked as a
dependency, and if the directory is created or delete the rule will rerun in subsequent builds.
You should not call doesDirectoryExist on directories which can be created by the build system.
doesFileExist :: FilePath -> Action Bool #
Returns True if the file exists. The existence of the file is tracked as a
dependency, and if the file is created or deleted the rule will rerun in subsequent builds.
You should not call doesFileExist on files which can be created by the build system.
(&?>) :: (FilePath -> Maybe [FilePath]) -> ([FilePath] -> Action ()) -> Rules () infix 1 #
Define a rule for building multiple files at the same time, a more powerful
and more dangerous version of &%>. Think of it as the AND (&&) equivalent of ?>.
Given an application test &?> ..., test should return Just if the rule applies, and should
return the list of files that will be produced. This list must include the file passed as an argument and should
obey the invariant:
forAll $ \x ys -> test x == Just ys ==> x `elem` ys && all ((== Just ys) . test) ys
As an example of a function satisfying the invariaint:
test x |takeExtensionx `elem` [".hi",".o"] = Just [dropExtensionx<.>"hi",dropExtensionx<.>"o"] test _ = Nothing
Regardless of whether Foo.hi or Foo.o is passed, the function always returns [Foo.hi, Foo.o].
(&%>) :: [FilePattern] -> ([FilePath] -> Action ()) -> Rules () infix 1 #
Define a rule for building multiple files at the same time.
Think of it as the AND (&&) equivalent of %>.
As an example, a single invocation of GHC produces both .hi and .o files:
["*.o","*.hi"]&%>\[o,hi] -> do let hs = o-<.>"hs"need... -- all files the .hs importcmd"ghc -c" [hs]
However, in practice, it's usually easier to define rules with %> and make the .hi depend
on the .o. When defining rules that build multiple files, all the FilePattern values must
have the same sequence of // and * wildcards in the same order.
This function will create directories for the result files, if necessary.
orderOnly :: [FilePath] -> Action () #
Define order-only dependencies, these are dependencies that will always be built before continuing, but which aren't dependencies of this action. Mostly useful for defining generated dependencies you think might be real dependencies. If they turn out to be real dependencies, you should add an explicit dependency afterwards.
"source.o" %> \out -> do
orderOnly ["header.h"]
cmd_ "gcc -c source.c -o source.o -MMD -MF source.m"
neededMakefileDependencies "source.m"
If header.h is included by source.c then the call to needMakefileDependencies will cause
it to be added as a real dependency. If it isn't, then the rule won't rebuild if it changes.
(%>) :: FilePattern -> (FilePath -> Action ()) -> Rules () infix 1 #
Define a rule that matches a FilePattern, see ?== for the pattern rules.
Patterns with no wildcards have higher priority than those with wildcards, and no file
required by the system may be matched by more than one pattern at the same priority
(see priority and alternatives to modify this behaviour).
This function will create the directory for the result file, if necessary.
"*.asm.o"%>\out -> do let src =dropExtensionoutneed[src]cmd"as" [src] "-o" [out]
To define a build system for multiple compiled languages, we recommend using .asm.o,
.cpp.o, .hs.o, to indicate which language produces an object file.
I.e., the file foo.cpp produces object file foo.cpp.o.
Note that matching is case-sensitive, even on Windows.
If the Action completes successfully the file is considered up-to-date, even if the file
has not changed.
(?>) :: (FilePath -> Bool) -> (FilePath -> Action ()) -> Rules () infix 1 #
Define a rule to build files. If the first argument returns True for a given file,
the second argument will be used to build it. Usually %> is sufficient, but ?> gives
additional power. For any file used by the build system, only one rule should return True.
This function will create the directory for the result file, if necessary.
(all isUpper .takeBaseName)?>\out -> do let src =replaceBaseNameout $ map toLower $ takeBaseName outwriteFile'out . map toUpper =<<readFile'src
If the Action completes successfully the file is considered up-to-date, even if the file
has not changed.
(~>) :: String -> Action () -> Rules () infix 1 #
Infix operator alias for phony, for sake of consistency with normal
rules.
phony :: String -> Action () -> Rules () #
Declare a Make-style phony action. A phony target does not name
a file (despite living in the same namespace as file rules);
rather, it names some action to be executed when explicitly
requested. You can demand phony rules using want. (And need,
although that's not recommended.)
Phony actions are intended to define recipes that can be executed
by the user. If you need a phony action in a rule then every
execution where that rule is required will rerun both the rule and
the phony action. However, note that phony actions are never
executed more than once in a single build run.
In make, the .PHONY attribute on non-file-producing rules has a
similar effect. However, while in make it is acceptable to omit
the .PHONY attribute as long as you don't create the file in
question, a Shake rule which behaves this way will fail lint.
Use a phony rule! For file-producing rules which should be
rerun every execution of Shake, see alwaysRerun.
want :: [FilePath] -> Rules () #
Require that the argument files are built by the rules, used to specify the target.
main =shakeshakeOptions$ dowant["Main.exe"] ...
This program will build Main.exe, given sufficient rules. All arguments to all want calls
may be built in parallel, in any order.
This function is defined in terms of action and need, use action if you need more complex
targets than want allows.
trackAllow :: [FilePattern] -> Action () #
Allow accessing a file in this rule, ignoring any trackRead / trackWrite calls matching
the pattern.
trackWrite :: [FilePath] -> Action () #
Track that a file was written by the action preceeding it. If shakeLint is activated
then these files must either be the target of this rule, or never referred to by the build system.
Calls to trackWrite are automatically inserted in LintFSATrace mode.
trackRead :: [FilePath] -> Action () #
Track that a file was read by the action preceeding it. If shakeLint is activated
then these files must be dependencies of this rule. Calls to trackRead are
automatically inserted in LintFSATrace mode.
needHasChanged :: [FilePath] -> Action [FilePath] #
Like need but returns a list of rebuild dependencies this build.
The following example writes a list of changed dependencies to a file as its action.
"target"%>\out -> do let sourceList = ["source1", "source2"] rebuildList <-needHasChangedsourceListwriteFileLinesout rebuildList
This function can be used to alter the action depending on which dependency needed to be rebuild.
Note that a rule can be run even if no dependency has changed, for example
because of shakeRebuild or because the target has changed or been deleted.
To detect the latter case you may wish to use resultHasChanged.
need :: [FilePath] -> Action () #
Add a dependency on the file arguments, ensuring they are built before continuing.
The file arguments may be built in parallel, in any order. This function is particularly
necessary when calling cmd or command. As an example:
"//*.rot13"%>\out -> do let src =dropExtensionoutneed[src]cmd"rot13" [src] "-o" [out]
Usually need [foo,bar] is preferable to need [foo] >> need [bar] as the former allows greater
parallelism, while the latter requires foo to finish building before starting to build bar.
This function should not be called with wildcards (e.g. *.txt - use getDirectoryFiles to expand them),
environment variables (e.g. $HOME - use getEnv to expand them) or directories (directories cannot be
tracked directly - track files within the directory instead).
resultHasChanged :: FilePath -> Action Bool #
Has a file changed. This function will only give the correct answer if called in the rule
producing the file, before the rule has modified the file in question.
Best avoided, but sometimes necessary in conjunction with needHasChanged to cause rebuilds
to happen if the result is deleted or modified.
askOracle :: (RuleResult q ~ a, ShakeValue q, ShakeValue a) => q -> Action a #
Get information previously added with addOracle or addOracleCache.
The question/answer types must match those provided previously.
addOracleCache :: (RuleResult q ~ a, ShakeValue q, ShakeValue a) => (q -> Action a) -> Rules (q -> Action a) #
A combination of addOracle and newCache - an action that only runs when its dependencies change,
whose result is stored in the database.
- Does the information need recomputing every time? e.g. looking up stuff in the environment?
If so, use
addOracleinstead. - Is the action mostly deserisalising some file? If so, use
newCache. - Is the operation expensive computation from other results? If so, use
addOracleCache.
An alternative to using addOracleCache is introducing an intermediate file containing the result,
which requires less storage in the Shake database and can be inspected by existing file-system viewing
tools.
addOracle :: (RuleResult q ~ a, ShakeValue q, ShakeValue a) => (q -> Action a) -> Rules (q -> Action a) #
Add extra information which rules can depend on.
An oracle is a function from a question type q, to an answer type a.
As an example, we can define an oracle allowing you to depend on the current version of GHC:
newtype GhcVersion = GhcVersion () deriving (Show,Typeable,Eq,Hashable,Binary,NFData)
type instance RuleResult GhcVersion = String
rules = do
addOracle $ \(GhcVersion _) -> fmap fromStdout $ cmd "ghc --numeric-version" :: Action String
... rules ...
If a rule calls askOracle (GhcVersion ())
- We define
GhcVersionwith anewtypearound(), allowing the use ofGeneralizedNewtypeDeriving. All the necessary type classes are exported from Development.Shake.Classes. - The
type instancerequires the extensionTypeFamilies. - Each call to
addOraclemust use a different type of question. - Actions passed to
addOraclewill be run in every build they are required, even if nothing else changes, so be careful of slow actions. If the result of an oracle does not change it will not invalidate any rules depending on it. To always rerun files rules seealwaysRerun. - If the value returned by
askOracleis ignored thenaskOracleWithmay help avoid ambiguous type messages. Alternatively, use the result ofaddOracle, which isaskOraclerestricted to the correct type.
As a more complex example, consider tracking Haskell package versions:
newtype GhcPkgList = GhcPkgList () deriving (Show,Typeable,Eq,Hashable,Binary,NFData)
type instance RuleResult GhcPkgList = [(String, String)]
newtype GhcPkgVersion = GhcPkgVersion String deriving (Show,Typeable,Eq,Hashable,Binary,NFData)
type instance RuleResult GhcPkgVersion = Maybe String
rules = do
getPkgList <- addOracle $ \GhcPkgList{} -> do
Stdout out <- cmd "ghc-pkg list --simple-output"
return [(reverse b, reverse a) | x <- words out, let (a,_:b) = break (== '-') $ reverse x]
getPkgVersion <- addOracle $ \(GhcPkgVersion pkg) -> do
pkgs <- getPkgList $ GhcPkgList ()
return $ lookup pkg pkgs
"myrule" %> \_ -> do
getPkgVersion $ GhcPkgVersion "shake"
... rule using the shake version ...
Using these definitions, any rule depending on the version of shake
should call getPkgVersion $ GhcPkgVersion "shake" to rebuild when shake is upgraded.
alwaysRerun :: Action () #
Always rerun the associated action. Useful for defining rules that query the environment. For example:
"ghcVersion.txt"%>\out -> doalwaysRerunStdoutstdout <-cmd"ghc --numeric-version"writeFileChangedout stdout
In make, the .PHONY attribute on file-producing rules has a similar effect.
Note that alwaysRerun is applied when a rule is executed. Modifying an existing rule
to insert alwaysRerun will not cause that rule to rerun next time.
batch :: Int -> ((a -> Action ()) -> Rules ()) -> (a -> Action b) -> ([b] -> Action ()) -> Rules () #
Batch different outputs into a single Action, typically useful when a command has a high
startup cost - e.g. apt-get install foo bar baz is a lot cheaper than three separate
calls to apt-get install. As an example, if we have a standard build rule:
"*.out"%>\out -> doneed[out-<.>"in"]cmd"build-multiple" [out-<.>"in"]
Assuming that build-multiple can compile multiple files in a single run,
and that the cost of doing so is a lot less than running each individually,
we can write:
batch3 ("*.out"%>) (\out -> doneed[out-<.>"in"]; return out) (\outs ->cmd"build-multiple" [out-<.>"in" | out <- outs])
In constrast to the normal call, we have specified a maximum batch size of 3,
an action to run on each output individually (typically all the need dependencies),
and an action that runs on multiple files at once. If we were to require lots of
*.out files, they would typically be built in batches of 3.
If Shake ever has nothing else to do it will run batches before they are at the maximum, so you may see much smaller batches, especially at high parallelism settings.
orderOnlyAction :: Action a -> Action a #
Run an action but do not depend on anything the action uses.
A more general version of orderOnly.
parallel :: [Action a] -> Action [a] #
Execute a list of actions in parallel. In most cases need will be more appropriate to benefit from parallelism.
unsafeExtraThread :: Action a -> Action a #
Run an action without counting to the thread limit, typically used for actions that execute
on remote machines using barely any local CPU resources.
Unsafe as it allows the shakeThreads limit to be exceeded.
You cannot depend on a rule (e.g. need) while the extra thread is executing.
If the rule blocks (e.g. calls withResource) then the extra thread may be used by some other action.
Only really suitable for calling cmd / command.
withResource :: Resource -> Int -> Action a -> Action a #
Run an action which uses part of a finite resource. For more details see Resource.
You cannot depend on a rule (e.g. need) while a resource is held.
traced :: String -> IO a -> Action a #
Write an action to the trace list, along with the start/end time of running the IO action.
The cmd and command functions automatically call traced.
The trace list is used for profile reports (see shakeReport).
By default traced prints some useful extra context about what
Shake is building, e.g.:
# traced message (for myobject.o)
To suppress the output of traced (for example you want more control
over the message using putNormal), use the quietly combinator.
quietly :: Action a -> Action a #
Run an action with Quiet verbosity, in particular messages produced by traced
(including from cmd or command) will not be printed to the screen.
Will not update the shakeVerbosity returned by getShakeOptions and will
not turn off any Diagnostic tracing.
withVerbosity :: Verbosity -> Action a -> Action a #
Run an action with a particular verbosity level.
Will not update the shakeVerbosity returned by getShakeOptions and will
not have any impact on Diagnostic tracing.
getVerbosity :: Action Verbosity #
Get the current verbosity level, originally set by shakeVerbosity. If you
want to output information to the console, you are recommended to use
putLoud / putNormal / putQuiet, which ensures multiple messages are
not interleaved. The verbosity can be modified locally by withVerbosity.
putQuiet :: String -> Action () #
Write an important message to the output, only supressed when shakeVerbosity is Silent.
The output will not be interleaved with any other Shake messages (other than those generated by system commands).
putNormal :: String -> Action () #
Write a normal priority message to the output, only supressed when shakeVerbosity is Quiet or Silent.
The output will not be interleaved with any other Shake messages (other than those generated by system commands).
putLoud :: String -> Action () #
Write an unimportant message to the output, only shown when shakeVerbosity is higher than normal (Loud or above).
The output will not be interleaved with any other Shake messages (other than those generated by system commands).
runAfter :: IO () -> Action () #
Specify an action to be run after the database has been closed, if building completes successfully.
getProgress :: Action Progress #
Get the current Progress structure, as would be returned by shakeProgress.
getShakeOptions :: Action ShakeOptions #
Get the initial ShakeOptions, these will not change during the build process.
actionFinally :: Action a -> IO b -> Action a #
actionOnException :: Action a -> IO b -> Action a #
withoutActions :: Rules () -> Rules () #
Remove all actions specified in a set of rules, usually used for implementing command line specification of what to build.
action :: Action a -> Rules () #
Run an action, usually used for specifying top-level requirements.
main =shakeshakeOptions$ doaction$ do b <-doesFileExist"file.src" when b $need["file.out"]
This action builds file.out, but only if file.src exists. The action
will be run in every build execution (unless withoutActions is used), so only cheap
operations should be performed. All arguments to action may be run in parallel, in any order.
For the standard requirement of only needing a fixed list of files in the action,
see want.
alternatives :: Rules () -> Rules () #
Change the matching behaviour of rules so rules do not have to be disjoint, but are instead matched in order. Only recommended for small blocks containing a handful of rules.
alternatives$ do "hello.*" %> \out ->writeFile'out "hello.*" "*.txt" %> \out ->writeFile'out "*.txt"
In this example hello.txt will match the first rule, instead of raising an error about ambiguity.
Inside alternatives the priority of each rule is not used to determine which rule matches,
but the resulting match uses that priority compared to the rules outside the alternatives block.
priority :: Double -> Rules () -> Rules () #
Change the priority of a given set of rules, where higher priorities take precedence.
All matching rules at a given priority must be disjoint, or an error is raised.
All builtin Shake rules have priority between 0 and 1.
Excessive use of priority is discouraged. As an example:
priority4 $ "hello.*" %> \out ->writeFile'out "hello.*"priority8 $ "*.txt" %> \out ->writeFile'out "*.txt"
In this example hello.txt will match the second rule, instead of raising an error about ambiguity.
The priority function obeys the invariants:
priorityp1 (priorityp2 r1) ===priorityp1 r1priorityp1 (r1 >> r2) ===priorityp1 r1 >>priorityp1 r2
getShakeOptionsRules :: Rules ShakeOptions #
Get the ShakeOptions that were used.
Define a set of rules. Rules can be created with calls to functions such as %> or action.
Rules are combined with either the Monoid instance, or (more commonly) the Monad instance and do notation.
To define your own custom types of rule, see Development.Shake.Rule.
type family RuleResult key :: * #
Instances
| type RuleResult FileQ | |
Defined in Development.Shake.Internal.Rules.File type RuleResult FileQ = FileR | |
| type RuleResult DoesDirectoryExistQ | |
Defined in Development.Shake.Internal.Rules.Directory type RuleResult DoesDirectoryExistQ = DoesDirectoryExistA | |
| type RuleResult DoesFileExistQ | |
Defined in Development.Shake.Internal.Rules.Directory type RuleResult DoesFileExistQ = DoesFileExistA | |
| type RuleResult GetDirectoryContentsQ | |
Defined in Development.Shake.Internal.Rules.Directory type RuleResult GetDirectoryContentsQ = GetDirectoryA | |
| type RuleResult GetDirectoryDirsQ | |
Defined in Development.Shake.Internal.Rules.Directory type RuleResult GetDirectoryDirsQ = GetDirectoryA | |
| type RuleResult GetDirectoryFilesQ | |
Defined in Development.Shake.Internal.Rules.Directory type RuleResult GetDirectoryFilesQ = GetDirectoryA | |
| type RuleResult GetEnvQ | |
Defined in Development.Shake.Internal.Rules.Directory type RuleResult GetEnvQ = GetEnvA | |
| type RuleResult FilesQ | |
Defined in Development.Shake.Internal.Rules.Files type RuleResult FilesQ = FilesA | |
| type RuleResult AlwaysRerunQ | |
Defined in Development.Shake.Internal.Rules.Rerun type RuleResult AlwaysRerunQ = () | |
| type RuleResult (OracleQ a) | |
Defined in Development.Shake.Internal.Rules.Oracle | |
The Action monad, use liftIO to raise IO actions into it, and need to execute files.
Action values are used by addUserRule and action. The Action monad tracks the dependencies of a rule.
To raise an exception call error, fail or liftIO . throwIO
Instances
| Monad Action | |
| Functor Action | |
| MonadFail Action | |
Defined in Development.Shake.Internal.Core.Types | |
| Applicative Action | |
| MonadIO Action | |
Defined in Development.Shake.Internal.Core.Types | |
| CmdResult r => CmdArguments (Action r) | |
Defined in Development.Shake.Command Methods cmdArguments :: CmdArgument -> Action r # | |
shakeOptions :: ShakeOptions #
The default set of ShakeOptions.
The current assumptions made by the build system, used by shakeRebuild. These options
allow the end user to specify that any rules run are either to be treated as clean, or as
dirty, regardless of what the build system thinks.
These assumptions only operate on files reached by the current action commands. Any
other files in the database are left unchanged.
Constructors
| RebuildNow | Assume these files are dirty and require rebuilding. for benchmarking rebuild speed and for rebuilding if untracked dependencies have changed. This flag is safe, but may cause more rebuilding than necessary. |
| RebuildNormal | Useful to reset the rebuild status to how it was before, equivalent to passing no |
| RebuildLater | This assumption is unsafe, and may lead to incorrect build results in this run. Assume these files are clean in this run, but test them normally in future runs. |
Instances
| Bounded Rebuild | |
| Enum Rebuild | |
| Eq Rebuild | |
| Data Rebuild | |
Defined in Development.Shake.Internal.Options Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Rebuild -> c Rebuild # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Rebuild # toConstr :: Rebuild -> Constr # dataTypeOf :: Rebuild -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Rebuild) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Rebuild) # gmapT :: (forall b. Data b => b -> b) -> Rebuild -> Rebuild # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Rebuild -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Rebuild -> r # gmapQ :: (forall d. Data d => d -> u) -> Rebuild -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Rebuild -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Rebuild -> m Rebuild # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Rebuild -> m Rebuild # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Rebuild -> m Rebuild # | |
| Ord Rebuild | |
Defined in Development.Shake.Internal.Options | |
| Read Rebuild | |
| Show Rebuild | |
Which lint checks to perform, used by shakeLint.
Constructors
| LintBasic | The most basic form of linting. Checks that the current directory does not change and that results do not change after they
are first written. Any calls to |
| LintFSATrace | Track which files are accessed by command line programs using fsatrace. |
Instances
| Bounded Lint | |
| Enum Lint | |
Defined in Development.Shake.Internal.Options | |
| Eq Lint | |
| Data Lint | |
Defined in Development.Shake.Internal.Options Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Lint -> c Lint # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Lint # dataTypeOf :: Lint -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Lint) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Lint) # gmapT :: (forall b. Data b => b -> b) -> Lint -> Lint # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Lint -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Lint -> r # gmapQ :: (forall d. Data d => d -> u) -> Lint -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Lint -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Lint -> m Lint # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Lint -> m Lint # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Lint -> m Lint # | |
| Ord Lint | |
| Read Lint | |
| Show Lint | |
How should you determine if a file has changed, used by shakeChange. The most common values are
ChangeModtime (the default, very fast, touch causes files to rebuild) and ChangeModtimeAndDigestInput
(slightly slower, touch and switching git branches does not cause input files to rebuild).
Constructors
| ChangeModtime | Compare equality of modification timestamps, a file has changed if its last modified time changes.
A |
| ChangeDigest | Compare equality of file contents digests, a file has changed if its digest changes.
A |
| ChangeModtimeAndDigest | A file is rebuilt if both its modification time and digest have changed. For efficiency reasons, the modification time is checked first, and if that has changed, the digest is checked. |
| ChangeModtimeAndDigestInput | Use |
| ChangeModtimeOrDigest | A file is rebuilt if either its modification time or its digest has changed. A |
Instances
| Bounded Change | |
| Enum Change | |
Defined in Development.Shake.Internal.Options | |
| Eq Change | |
| Data Change | |
Defined in Development.Shake.Internal.Options Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Change -> c Change # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Change # toConstr :: Change -> Constr # dataTypeOf :: Change -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Change) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Change) # gmapT :: (forall b. Data b => b -> b) -> Change -> Change # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Change -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Change -> r # gmapQ :: (forall d. Data d => d -> u) -> Change -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Change -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Change -> m Change # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Change -> m Change # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Change -> m Change # | |
| Ord Change | |
| Read Change | |
| Show Change | |
data ShakeOptions #
Options to control the execution of Shake, usually specified by overriding fields in
shakeOptions:
shakeOptions{shakeThreads=4,shakeReport=["report.html"]}
The Data instance for this type reports the shakeProgress and shakeOutput fields as having the abstract type Hidden,
because Data cannot be defined for functions or TypeReps.
Constructors
| ShakeOptions | |
Fields
| |
Instances
| Data ShakeOptions | |
Defined in Development.Shake.Internal.Options Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> ShakeOptions -> c ShakeOptions # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c ShakeOptions # toConstr :: ShakeOptions -> Constr # dataTypeOf :: ShakeOptions -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c ShakeOptions) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c ShakeOptions) # gmapT :: (forall b. Data b => b -> b) -> ShakeOptions -> ShakeOptions # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> ShakeOptions -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> ShakeOptions -> r # gmapQ :: (forall d. Data d => d -> u) -> ShakeOptions -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> ShakeOptions -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> ShakeOptions -> m ShakeOptions # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> ShakeOptions -> m ShakeOptions # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> ShakeOptions -> m ShakeOptions # | |
| Show ShakeOptions | |
Defined in Development.Shake.Internal.Options Methods showsPrec :: Int -> ShakeOptions -> ShowS # show :: ShakeOptions -> String # showList :: [ShakeOptions] -> ShowS # | |
The verbosity data type, used by shakeVerbosity.
Constructors
| Silent | Don't print any messages. |
| Quiet | Only print essential messages, typically errors. |
| Normal | Print errors and |
| Loud | Print errors and full command lines when running a |
| Chatty | Print errors, full command line and status messages when starting a rule. |
| Diagnostic | Print messages for virtually everything (mostly for debugging). |
Instances
progressSimple :: IO Progress -> IO () #
A simple method for displaying progress messages, suitable for using as shakeProgress.
This function writes the current progress to the titlebar every five seconds using progressTitlebar,
and calls any shake-progress program on the $PATH using progressProgram.
progressProgram :: IO (String -> IO ()) #
Call the program shake-progress if it is on the $PATH. The program is called with
the following arguments:
--title=string- the string passed toprogressProgram.--state=Normal, or one ofNoProgress,Normal, orErrorto indicate what state the progress bar should be in.--value=25- the percent of the build that has completed, if not inNoProgressstate.
The program will not be called consecutively with the same --state and --value options.
Windows 7 or higher users can get taskbar progress notifications by placing the following
program in their $PATH: https://github.com/ndmitchell/shake/releases.
progressTitlebar :: String -> IO () #
Set the title of the current console window to the given text. If the
environment variable $TERM is set to xterm this uses xterm escape sequences.
On Windows, if not detected as an xterm, this function uses the SetConsoleTitle API.
progressDisplay :: Double -> (String -> IO ()) -> IO Progress -> IO () #
Given a sampling interval (in seconds) and a way to display the status message,
produce a function suitable for using as shakeProgress.
This function polls the progress information every n seconds, produces a status
message and displays it using the display function.
Typical status messages will take the form of 1m25s (15%), indicating that the build
is predicted to complete in 1 minute 25 seconds (85 seconds total), and 15% of the necessary build time has elapsed.
This function uses past observations to predict future behaviour, and as such, is only
guessing. The time is likely to go up as well as down, and will be less accurate from a
clean build (as the system has fewer past observations).
The current implementation is to predict the time remaining (based on timeTodo) and the
work already done (timeBuilt). The percentage is then calculated as remaining / (done + remaining),
while time left is calculated by scaling remaining by the observed work rate in this build,
roughly done / time_elapsed.
Information about the current state of the build, obtained by either passing a callback function
to shakeProgress (asynchronous output) or getProgress
(synchronous output). Typically a build system will pass progressDisplay to shakeProgress,
which will poll this value and produce status messages.
Constructors
| Progress | |
Fields
| |
Instances
| Eq Progress | |
| Data Progress | |
Defined in Development.Shake.Internal.Progress Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Progress -> c Progress # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Progress # toConstr :: Progress -> Constr # dataTypeOf :: Progress -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Progress) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Progress) # gmapT :: (forall b. Data b => b -> b) -> Progress -> Progress # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Progress -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Progress -> r # gmapQ :: (forall d. Data d => d -> u) -> Progress -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Progress -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Progress -> m Progress # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Progress -> m Progress # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Progress -> m Progress # | |
| Ord Progress | |
Defined in Development.Shake.Internal.Progress | |
| Read Progress | |
| Show Progress | |
| Semigroup Progress | |
| Monoid Progress | |
newThrottleIO :: String -> Int -> Double -> IO Resource #
A version of newThrottle that runs in IO, and can be called before calling shake.
Most people should use newThrottle instead.
newResourceIO :: String -> Int -> IO Resource #
A version of newResource that runs in IO, and can be called before calling shake.
Most people should use newResource instead.
A type representing an external resource which the build system should respect. There
are two ways to create Resources in Shake:
newResourcecreates a finite resource, stopping too many actions running simultaneously.newThrottlecreates a throttled resource, stopping too many actions running over a short time period.
These resources are used with withResource when defining rules. Typically only
system commands (such as cmd) should be run inside withResource,
not commands such as need.
Be careful that the actions run within withResource do not themselves require further
resources, or you may get a "thread blocked indefinitely in an MVar operation" exception.
If an action requires multiple resources, use withResources to avoid deadlock.
type ShakeValue a = (Show a, Typeable a, Eq a, Hashable a, Binary a, NFData a) #
Define an alias for the six type classes required for things involved in Shake rules.
Using this alias requires the ConstraintKinds extension.
To define your own values meeting the necessary constraints it is convenient to use the extensions
GeneralizedNewtypeDeriving and DeriveDataTypeable to write:
newtype MyType = MyType (String, Bool) deriving (Show, Typeable, Eq, Hashable, Binary, NFData)
Shake needs these instances on keys and values. They are used for:
Showis used to print out keys in errors, profiling, progress messages and diagnostics.Typeableis used because Shake indexes its database by the type of the key and value involved in the rule (overlap is not allowed for type classes and not allowed in Shake either).EqandHashableare used on keys in order to build hash maps from keys to values.Eqis used on values to test if the value has changed or not (this is used to support unchanging rebuilds, where Shake can avoid rerunning rules if it runs a dependency, but it turns out that no changes occurred.) TheHashableinstances are only use at runtime (never serialised to disk), so they do not have to be stable across runs. Hashable on values is not used, and only required for a consistent interface.Binaryis used to serialize keys and values into Shake's build database; this lets Shake cache values across runs and implement unchanging rebuilds.NFDatais used to avoid space and thunk leaks, especially when Shake is parallelized.
filePattern :: FilePattern -> FilePath -> Maybe [String] #
Like ?==, but returns Nothing on if there is no match, otherwise Just with the list
of fragments matching each wildcard. For example:
filePattern"**/*.c" "test.txt" == NothingfilePattern"**/*.c" "foo.c" == Just ["","foo"]filePattern"**/*.c" "bar/baz/foo.c" == Just ["bar/baz/","foo"]
Note that the ** will often contain a trailing /, and even on Windows any
\ separators will be replaced by /.
(?==) :: FilePattern -> FilePath -> Bool #
Match a FilePattern against a FilePath, There are three special forms:
*matches an entire path component, excluding any separators.//matches an arbitrary number of path components, including absolute path prefixes.**as a path component matches an arbitrary number of path components, but not absolute path prefixes. Currently considered experimental.
Some examples:
test.cmatchestest.cand nothing else.*.cmatches all.cfiles in the current directory, sofile.cmatches, butfile.handdir/file.cdon't.//*.cmatches all.cfiles anywhere on the filesystem, sofile.c,dir/file.c,dir1/dir2/file.cand/path/to/file.call match, butfile.handdir/file.hdon't.dir/*/*matches all files one level belowdir, sodir/one/file.canddir/two/file.hmatch, butfile.c,one/dir/file.c,dir/file.handdir/one/two/file.cdon't.
Patterns with constructs such as foo/../bar will never match
normalised FilePath values, so are unlikely to be correct.
(<//>) :: FilePattern -> FilePattern -> FilePattern infixr 5 #
Join two FilePattern values by inserting two / characters between them.
Will first remove any trailing path separators on the first argument, and any leading
separators on the second.
"dir" <//> "*" == "dir//*"
type FilePattern = String #
A type synonym for file patterns, containing // and *. For the syntax
and semantics of FilePattern see ?==.
Most normaliseExd FilePath values are suitable as FilePattern values which match
only that specific file. On Windows \ is treated as equivalent to /.
You can write FilePattern values as a literal string, or build them
up using the operators <.>, </>
and <//>. However, beware that:
- On Windows, use
<.>from Development.Shake.FilePath instead of from System.FilePath - otherwise"//*" <.> exeresults in"//*\\.exe". - If the second argument of
</>has a leading path separator (namely/) then the second argument will be returned.
data ShakeException #
Error representing all expected exceptions thrown by Shake. Problems when executing rules will be raising using this exception type.
Constructors
| ShakeException | |
Fields
| |
Instances
| Show ShakeException | |
Defined in Development.Shake.Internal.Errors Methods showsPrec :: Int -> ShakeException -> ShowS # show :: ShakeException -> String # showList :: [ShakeException] -> ShowS # | |
| Exception ShakeException | |
Defined in Development.Shake.Internal.Errors Methods toException :: ShakeException -> SomeException # | |
Options passed to command or cmd to control how processes are executed.
Constructors
| Cwd FilePath | Change the current directory in the spawned process. By default uses this processes current directory. |
| Env [(String, String)] | Change the environment variables in the spawned process. By default uses this processes environment. |
| AddEnv String String | Add an environment variable in the child process. |
| RemEnv String | Remove an environment variable from the child process. |
| AddPath [String] [String] | Add some items to the prefix and suffix of the |
| Stdin String | Given as the |
| StdinBS ByteString | Given as the |
| FileStdin FilePath | Take the |
| Shell | Pass the command to the shell without escaping - any arguments will be joined with spaces. By default arguments are escaped properly. |
| BinaryPipes | Treat the |
| Traced String | Name to use with |
| Timeout Double | Abort the computation after N seconds, will raise a failure exit code. Calls |
| WithStdout Bool | Should I include the |
| WithStderr Bool | Should I include the |
| EchoStdout Bool | Should I echo the |
| EchoStderr Bool | Should I echo the |
| FileStdout FilePath | Should I put the |
| FileStderr FilePath | Should I put the |
| AutoDeps | Compute dependencies automatically. |
Instances
| Eq CmdOption | |
| Data CmdOption | |
Defined in Development.Shake.Internal.CmdOption Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> CmdOption -> c CmdOption # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c CmdOption # toConstr :: CmdOption -> Constr # dataTypeOf :: CmdOption -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c CmdOption) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c CmdOption) # gmapT :: (forall b. Data b => b -> b) -> CmdOption -> CmdOption # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> CmdOption -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> CmdOption -> r # gmapQ :: (forall d. Data d => d -> u) -> CmdOption -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> CmdOption -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> CmdOption -> m CmdOption # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> CmdOption -> m CmdOption # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> CmdOption -> m CmdOption # | |
| Ord CmdOption | |
Defined in Development.Shake.Internal.CmdOption | |
| Show CmdOption | |
| IsCmdArgument CmdOption | |
Defined in Development.Shake.Command Methods toCmdArgument :: CmdOption -> CmdArgument # | |
| IsCmdArgument [CmdOption] | |
Defined in Development.Shake.Command Methods toCmdArgument :: [CmdOption] -> CmdArgument # | |
getFlag :: String -> Action Bool Source #
Wrapper round getting the environment that returns a bool if env is present.
cmdArgsDir :: FilePath -> String -> [String] -> Action String Source #
Run commands in a dir with return string.
cmdArgsDir_ :: FilePath -> String -> [String] -> Action () Source #
Run commands in a dir with no return.
stackExec_ :: FilePath -> String -> [String] -> Action () Source #
Stack exec command without return.
sshDir :: FilePath -> String -> [String] -> Action String Source #
SSH command in a remote directory.
sshDir_ :: FilePath -> String -> [String] -> Action () Source #
SSH command in a remote directory with no return.
fake :: FilePath -> [FilePattern] -> String -> ([FilePath] -> Action ()) -> Rules () Source #
Use a fake file to keep track of the last time an file-free action ran.
meta :: FilePath -> Action String -> Rules () Source #
Use a meta file to keep track of vitual content.
preprocess :: FilePattern -> FilePath -> Action [(String, String)] -> Rules () Source #
Preprocess a file with m4.
getHashedVersion :: FilePath -> [FilePattern] -> Action String Source #
Build a hash version from a directory and file pattern.
stackRules :: FilePath -> [FilePattern] -> Rules () Source #
Stack rules.
stackTargetRules :: FilePath -> String -> [FilePattern] -> Rules () Source #
Stack rules.
dockerRules :: FilePath -> [FilePattern] -> Rules () Source #
Docker rules.