-- Hoogle documentation, generated by Haddock -- See Hoogle, http://www.haskell.org/hoogle/ -- | A compatibility layer for base -- -- Provides functions available in later versions of base to a -- wider range of compilers, without requiring you to use CPP pragmas in -- your code. See the README for what is covered. Also see the -- changelog for recent changes. -- -- Note that base-compat does not add any orphan instances. -- There is a separate package, base-orphans, for that. -- -- In addition, base-compat does not backport any data types or -- type classes. See this section of the README for more -- info. -- -- base-compat is designed to have zero dependencies. For a -- version of base-compat that depends on compatibility -- libraries for a wider support window, see the -- base-compat-batteries package. Most of the modules in -- this library have the same names as in base-compat-batteries -- to make it easier to switch between the two. There also exist versions -- of each module with the suffix .Repl, which are distinct from -- anything in base-compat-batteries, to allow for easier use in -- GHCi. @package base-compat @version 0.12.0 module Control.Concurrent.Compat -- | Fork a thread and call the supplied function when the thread is about -- to terminate, with an exception or a returned value. The function is -- called with asynchronous exceptions masked. -- --

--   forkFinally action and_then =
--     mask $ \restore ->
--       forkIO $ try (restore action) >>= and_then
--

-- -- This function is useful for informing the parent when a child -- terminates, for example. forkFinally :: IO a -> (Either SomeException a -> IO ()) -> IO ThreadId -- | Like forkIOWithUnmask, but the child thread is a bound thread, -- as with forkOS. forkOSWithUnmask :: ((forall a. () => IO a -> IO a) -> IO ()) -> IO ThreadId -- | Reexports Control.Concurrent.Compat from a globally unique -- namespace. module Control.Concurrent.Compat.Repl module Control.Concurrent.MVar.Compat -- | Like withMVar, but the IO action in the second -- argument is executed with asynchronous exceptions masked. withMVarMasked :: MVar a -> (a -> IO b) -> IO b -- | Reexports Control.Concurrent.MVar.Compat from a globally unique -- namespace. module Control.Concurrent.MVar.Compat.Repl module Control.Exception.Compat -- | Throw an exception. Exceptions may be thrown from purely functional -- code, but may only be caught within the IO monad. throw :: forall (r :: RuntimeRep) (a :: TYPE r) e. Exception e => e -> a -- | Reexports Control.Exception.Compat from a globally unique -- namespace. module Control.Exception.Compat.Repl module Control.Monad.Compat -- | 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) otherwise. For example: -- --

--   >>> 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)
--

guard :: Alternative f => Bool -> f () -- | 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. -- -- 'join bss' can be understood as the do -- expression -- --

--   do bs <- bss
--      bs
--

-- --

Examples

-- -- A common use of join is to run an IO computation -- returned from an STM transaction, since STM transactions -- can't perform IO directly. Recall that -- --

--   atomically :: STM a -> IO a
--

-- -- is used to run STM transactions atomically. So, by specializing -- the types of atomically and join to -- --

--   atomically :: STM (IO b) -> IO (IO b)
--   join       :: IO (IO b)  -> IO b
--

-- -- we can compose them as -- --

--   join . atomically :: STM (IO b) -> IO b
--

-- -- to run an STM transaction and the IO action it returns. join :: Monad m => m (m a) -> m a -- | 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: -- --

Left identity return a >>= k = k -- a
Right identity m >>= return = -- m
Associativity m >>= (\x -> k x -- >>= h) = (m >>= k) >>= -- h

-- -- Furthermore, the Monad and Applicative operations should -- relate as follows: -- --

```
pure = return
```

m1 <*> m2 = m1 >>= (x1 -> m2
--   >>= (x2 -> return (x1 x2)))

-- -- The above laws imply: -- --

```
fmap f xs = xs >>= return .
--   f
```
```
(>>) = (*>)
```

-- -- 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. class Applicative m => Monad (m :: Type -> Type) -- | Sequentially compose two actions, passing any value produced by the -- first as an argument to the second. -- -- 'as >>= bs' can be understood as the do -- expression -- --

--   do a <- as
--      bs a
--

(>>=) :: Monad m => m a -> (a -> m b) -> m b -- | Sequentially compose two actions, discarding any value produced by the -- first, like sequencing operators (such as the semicolon) in imperative -- languages. -- -- 'as >> bs' can be understood as the do -- expression -- --

--   do as
--      bs
--

(>>) :: Monad m => m a -> m b -> m b -- | Inject a value into the monadic type. return :: Monad m => a -> m a infixl 1 >>= infixl 1 >> -- | A type f is a Functor if it provides a function fmap -- which, given any types a and b lets you apply any -- function from (a -> b) to turn an f a into an -- f b, preserving the structure of f. Furthermore -- f needs to adhere to the following: -- --

Identity fmap id == id
Composition fmap (f . g) == fmap f . -- fmap g

-- -- Note, that the second law follows from the free theorem of the type -- fmap and the first law, so you need only check that the former -- condition holds. class Functor (f :: Type -> Type) -- | Using ApplicativeDo: 'fmap f as' can be -- understood as the do expression -- --

--   do a <- as
--      pure (f a)
--

-- -- with an inferred Functor constraint. fmap :: Functor f => (a -> b) -> f a -> f b -- | Replace all locations in the input with the same value. The default -- definition is fmap . const, but this may be -- overridden with a more efficient version. -- -- Using ApplicativeDo: 'a <$ bs' can be -- understood as the do expression -- --

--   do bs
--      pure a
--

-- -- with an inferred Functor constraint. (<$) :: Functor f => a -> f b -> f a infixl 4 <$ -- | When a value is bound in do-notation, the pattern on the left -- hand side of <- might not match. In this case, this class -- provides a function to recover. -- -- A Monad without a MonadFail instance may only be used in -- conjunction with pattern that always match, such as newtypes, tuples, -- data types with only a single data constructor, and irrefutable -- patterns (~pat). -- -- Instances of MonadFail should satisfy the following law: -- fail s should be a left zero for >>=, -- --

--   fail s >>= f  =  fail s
--

-- -- If your Monad is also MonadPlus, a popular definition is -- --

--   fail _ = mzero
--

class Monad m => MonadFail (m :: Type -> Type) fail :: MonadFail m => String -> m a -- | 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_. mapM :: (Traversable t, Monad m) => (a -> m b) -> t a -> m (t b) -- | Evaluate each monadic action in the structure from left to right, and -- collect the results. For a version that ignores the results see -- sequence_. sequence :: (Traversable t, Monad m) => t (m a) -> m (t a) -- | Direct MonadPlus equivalent of filter. -- --

Examples

-- -- The filter function is just mfilter specialized to the -- list monad: -- --

--   filter = ( mfilter :: (a -> Bool) -> [a] -> [a] )
--

-- -- An example using mfilter with the Maybe monad: -- --

--   >>> mfilter odd (Just 1)
--   Just 1
--   >>> mfilter odd (Just 2)
--   Nothing
--

mfilter :: MonadPlus m => (a -> Bool) -> m a -> m a -- | Strict version of <$>. (<$!>) :: Monad m => (a -> b) -> m a -> m b infixl 4 <$!> -- | The reverse of when. unless :: Applicative f => Bool -> f () -> f () -- | Like replicateM, but discards the result. replicateM_ :: Applicative m => Int -> m a -> m () -- | replicateM n act performs the action n times, -- gathering the results. -- -- Using ApplicativeDo: 'replicateM 5 as' can be -- understood as the do expression -- --

--   do a1 <- as
--      a2 <- as
--      a3 <- as
--      a4 <- as
--      a5 <- as
--      pure [a1,a2,a3,a4,a5]
--

-- -- Note the Applicative constraint. replicateM :: Applicative m => Int -> m a -> m [a] -- | Like foldM, but discards the result. foldM_ :: (Foldable t, Monad m) => (b -> a -> m b) -> b -> t a -> m () -- | 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. -- -- Note: foldM is the same as foldlM foldM :: (Foldable t, Monad m) => (b -> a -> m b) -> b -> t a -> m b -- | zipWithM_ is the extension of zipWithM which ignores the -- final result. zipWithM_ :: Applicative m => (a -> b -> m c) -> [a] -> [b] -> m () -- | The zipWithM function generalizes zipWith to arbitrary -- applicative functors. zipWithM :: Applicative m => (a -> b -> m c) -> [a] -> [b] -> m [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 monad. mapAndUnzipM :: Applicative m => (a -> m (b, c)) -> [a] -> m ([b], [c]) -- | Repeat an action indefinitely. -- -- Using ApplicativeDo: 'forever as' can be -- understood as the pseudo-do expression -- --

--   do as
--      as
--      ..
--

-- -- with as repeating. -- --

Examples

-- -- A common use of forever is to process input from network -- sockets, Handles, and channels (e.g. MVar and -- Chan). -- -- For example, here is how we might implement an echo server, -- using forever both to listen for client connections on a -- network socket and to echo client input on client connection handles: -- --

--   echoServer :: Socket -> IO ()
--   echoServer socket = forever $ do
--     client <- accept socket
--     forkFinally (echo client) (\_ -> hClose client)
--     where
--       echo :: Handle -> IO ()
--       echo client = forever $
--         hGetLine client >>= hPutStrLn client
--

forever :: Applicative f => f a -> f b -- | Right-to-left composition of Kleisli arrows. -- (>=>), with the arguments flipped. -- -- Note how this operator resembles function composition -- (.): -- --

--   (.)   ::            (b ->   c) -> (a ->   b) -> a ->   c
--   (<=<) :: Monad m => (b -> m c) -> (a -> m b) -> a -> m c
--

(<=<) :: Monad m => (b -> m c) -> (a -> m b) -> a -> m c infixr 1 <=< -- | Left-to-right composition of Kleisli arrows. -- -- '(bs >=> cs) a' can be understood as the -- do expression -- --

--   do b <- bs a
--      cs b
--

(>=>) :: Monad m => (a -> m b) -> (b -> m c) -> a -> m c infixr 1 >=> -- | This generalizes the list-based filter function. filterM :: Applicative m => (a -> m Bool) -> [a] -> m [a] -- | forM is mapM with its arguments flipped. For a version -- that ignores the results see forM_. forM :: (Traversable t, Monad m) => t a -> (a -> m b) -> m (t b) -- | The sum of a collection of actions, generalizing concat. As of -- base 4.8.0.0, msum is just asum, specialized to -- MonadPlus. msum :: (Foldable t, MonadPlus m) => t (m a) -> m a -- | 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. sequence_ :: (Foldable t, Monad m) => t (m a) -> m () -- | forM_ is mapM_ with its arguments flipped. For a version -- that doesn't ignore the results see forM. -- -- As of base 4.8.0.0, forM_ is just for_, specialized to -- Monad. forM_ :: (Foldable t, Monad m) => t a -> (a -> m b) -> m () -- | Map each element of a structure to a monadic action, evaluate these -- actions from left to right, and ignore the results. For a version that -- doesn't ignore the results see mapM. -- -- As of base 4.8.0.0, mapM_ is just traverse_, specialized -- to Monad. mapM_ :: (Foldable t, Monad m) => (a -> m b) -> t a -> m () -- | void value discards or ignores the result of -- evaluation, such as the return value of an IO action. -- -- Using ApplicativeDo: 'void as' can be -- understood as the do expression -- --

--   do as
--      pure ()
--

-- -- with an inferred Functor constraint. -- --

Examples

-- -- Replace the contents of a Maybe Int with unit: -- --

--   >>> void Nothing
--   Nothing
--   
--   >>> void (Just 3)
--   Just ()
--

-- -- Replace the contents of an Either Int -- Int with unit, resulting in an Either -- 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
--

void :: Functor f => f a -> f () -- | In many situations, the liftM operations can be replaced by -- uses of ap, which promotes function application. -- --

--   return f `ap` x1 `ap` ... `ap` xn
--

-- -- is equivalent to -- --

--   liftMn f x1 x2 ... xn
--

ap :: Monad m => m (a -> b) -> m a -> m b -- | Promote a function to a monad, scanning the monadic arguments from -- left to right (cf. liftM2). 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. For example, -- --

--   liftM2 (+) [0,1] [0,2] = [0,2,1,3]
--   liftM2 (+) (Just 1) Nothing = Nothing
--

liftM2 :: Monad m => (a1 -> a2 -> r) -> m a1 -> m a2 -> m r -- | Promote a function to a monad. liftM :: Monad m => (a1 -> r) -> m a1 -> m r -- | 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. when :: Applicative f => Bool -> f () -> f () -- | Same as >>=, but with the arguments interchanged. (=<<) :: Monad m => (a -> m b) -> m a -> m b infixr 1 =<< -- | Monads that also support choice and failure. class (Alternative m, Monad m) => MonadPlus (m :: Type -> Type) -- | The identity of mplus. It should also satisfy the equations -- --

--   mzero >>= f  =  mzero
--   v >> mzero   =  mzero
--

-- -- The default definition is -- --

--   mzero = empty
--

mzero :: MonadPlus m => m a -- | An associative operation. The default definition is -- --

--   mplus = (<|>)
--

mplus :: MonadPlus m => m a -> m a -> m a -- | 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: -- --

Left identity return a >>= k = k -- a
Right identity m >>= return = -- m
Associativity m >>= (\x -> k x -- >>= h) = (m >>= k) >>= -- h

-- -- Furthermore, the Monad and Applicative operations should -- relate as follows: -- --

```
pure = return
```

m1 <*> m2 = m1 >>= (x1 -> m2
--   >>= (x2 -> return (x1 x2)))

-- -- The above laws imply: -- --

```
fmap f xs = xs >>= return .
--   f
```
```
(>>) = (*>)
```

-- -- 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. class Applicative m => Monad (m :: Type -> Type) -- | When a value is bound in do-notation, the pattern on the left -- hand side of <- might not match. In this case, this class -- provides a function to recover. -- -- A Monad without a MonadFail instance may only be used in -- conjunction with pattern that always match, such as newtypes, tuples, -- data types with only a single data constructor, and irrefutable -- patterns (~pat). -- -- Instances of MonadFail should satisfy the following law: -- fail s should be a left zero for >>=, -- --

--   fail s >>= f  =  fail s
--

-- -- If your Monad is also MonadPlus, a popular definition is -- --

--   fail _ = mzero
--

class Monad m => MonadFail (m :: Type -> Type) fail :: MonadFail m => String -> m a -- | Monads that also support choice and failure. class (Alternative m, Monad m) => MonadPlus (m :: Type -> Type) -- | The identity of mplus. It should also satisfy the equations -- --

--   mzero >>= f  =  mzero
--   v >> mzero   =  mzero
--

-- -- The default definition is -- --

--   mzero = empty
--

mzero :: MonadPlus m => m a -- | An associative operation. The default definition is -- --

--   mplus = (<|>)
--

mplus :: MonadPlus m => m a -> m a -> m a -- | Reexports Control.Monad.Compat from a globally unique -- namespace. module Control.Monad.Compat.Repl module Control.Monad.Fail.Compat -- | Reexports Control.Monad.Fail.Compat from a globally unique -- namespace. module Control.Monad.Fail.Compat.Repl module Control.Monad.IO.Class.Compat -- | Reexports Control.Monad.IO.Class.Compat from a globally unique -- namespace. module Control.Monad.IO.Class.Compat.Repl module Control.Monad.ST.Lazy.Unsafe.Compat unsafeInterleaveST :: ST s a -> ST s a unsafeIOToST :: IO a -> ST s a -- | Reexports Control.Monad.ST.Lazy.Unsafe.Compat from a globally -- unique namespace. module Control.Monad.ST.Lazy.Unsafe.Compat.Repl module Control.Monad.ST.Unsafe.Compat -- | unsafeInterleaveST allows an ST computation to be -- deferred lazily. When passed a value of type ST a, the -- ST computation will only be performed when the value of the -- a is demanded. unsafeInterleaveST :: ST s a -> ST s a -- | Convert an IO action to an ST action. This relies on -- IO and ST having the same representation modulo the -- constraint on the state thread type parameter. unsafeIOToST :: IO a -> ST s a -- | Convert an ST action to an IO action. This relies on -- IO and ST having the same representation modulo the -- constraint on the state thread type parameter. -- -- For an example demonstrating why this is unsafe, see -- https://mail.haskell.org/pipermail/haskell-cafe/2009-April/060719.html unsafeSTToIO :: ST s a -> IO a -- | Reexports Control.Monad.ST.Unsafe.Compat from a globally unique -- namespace. module Control.Monad.ST.Unsafe.Compat.Repl module Data.Bifoldable.Compat -- | Reexports Data.Bifoldable.Compat from a globally unique -- namespace. module Data.Bifoldable.Compat.Repl module Data.Bifunctor.Compat -- | Reexports Data.Bifunctor.Compat from a globally unique -- namespace. module Data.Bifunctor.Compat.Repl module Data.Bitraversable.Compat -- | Reexports Data.Bitraversable.Compat from a globally unique -- namespace. module Data.Bitraversable.Compat.Repl module Data.Bits.Compat -- | Default implementation for bit. -- -- Note that: bitDefault i = 1 shiftL i bitDefault :: (Bits a, Num a) => Int -> a -- | Default implementation for testBit. -- -- Note that: testBitDefault x i = (x .&. bit i) /= 0 testBitDefault :: (Bits a, Num a) => a -> Int -> Bool -- | Default implementation for popCount. -- -- This implementation is intentionally naive. Instances are expected to -- provide an optimized implementation for their size. popCountDefault :: (Bits a, Num a) => a -> Int -- | Attempt to convert an Integral type a to an -- Integral type b using the size of the types as -- measured by Bits methods. -- -- A simpler version of this function is: -- --

--   toIntegral :: (Integral a, Integral b) => a -> Maybe b
--   toIntegral x
--     | toInteger x == y = Just (fromInteger y)
--     | otherwise        = Nothing
--     where
--       y = toInteger x
--

-- -- This version requires going through Integer, which can be -- inefficient. However, toIntegralSized is optimized to allow -- GHC to statically determine the relative type sizes (as measured by -- bitSizeMaybe and isSigned) and avoid going through -- Integer for many types. (The implementation uses -- fromIntegral, which is itself optimized with rules for -- base types but may go through Integer for some type -- pairs.) toIntegralSized :: (Integral a, Integral b, Bits a, Bits b) => a -> Maybe b -- | Reexports Data.Bits.Compat from a globally unique namespace. module Data.Bits.Compat.Repl module Data.Bool.Compat -- | Case analysis for the Bool type. bool x y p -- evaluates to x 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 p and if p then y else -- x are equivalent: -- --

--   >>> let p = True; x = "bar"; y = "foo"
--   
--   >>> bool x y p == if p then y else x
--   True
--   
--   >>> let p = False
--   
--   >>> bool x y p == if p then y else x
--   True
--

bool :: a -> a -> Bool -> a -- | Reexports Data.Bool.Compat from a globally unique namespace. module Data.Bool.Compat.Repl module Data.Complex.Compat -- | Reexports Data.Complex.Compat from a globally unique namespace. module Data.Complex.Compat.Repl module Data.Either.Compat -- | Return True if the given value is a Left-value, -- False otherwise. -- --

Examples

-- -- Basic usage: -- --

--   >>> isLeft (Left "foo")
--   True
--   
--   >>> isLeft (Right 3)
--   False
--

-- -- Assuming a Left value signifies some sort of error, we can use -- isLeft to write a very simple error-reporting function that -- does absolutely nothing in the case of success, and outputs "ERROR" if -- any error occurred. -- -- This example shows how isLeft might be used to avoid pattern -- matching when one does not care about the value contained in the -- constructor: -- --

--   >>> import Control.Monad ( when )
--   
--   >>> let report e = when (isLeft e) $ putStrLn "ERROR"
--   
--   >>> report (Right 1)
--   
--   >>> report (Left "parse error")
--   ERROR
--

isLeft :: Either a b -> Bool -- | Return True if the given value is a Right-value, -- False otherwise. -- --

Examples

-- -- Basic usage: -- --

--   >>> isRight (Left "foo")
--   False
--   
--   >>> isRight (Right 3)
--   True
--

-- -- Assuming a Left value signifies some sort of error, we can use -- isRight to write a very simple reporting function that only -- outputs "SUCCESS" when a computation has succeeded. -- -- This example shows how isRight might be used to avoid pattern -- matching when one does not care about the value contained in the -- constructor: -- --

--   >>> import Control.Monad ( when )
--   
--   >>> let report e = when (isRight e) $ putStrLn "SUCCESS"
--   
--   >>> report (Left "parse error")
--   
--   >>> report (Right 1)
--   SUCCESS
--

isRight :: Either a b -> Bool -- | Return the contents of a Left-value or a default value -- otherwise. -- --

Examples

-- -- Basic usage: -- --

--   >>> fromLeft 1 (Left 3)
--   3
--   
--   >>> fromLeft 1 (Right "foo")
--   1
--

fromLeft :: a -> Either a b -> a -- | Return the contents of a Right-value or a default value -- otherwise. -- --

Examples

-- -- Basic usage: -- --

--   >>> fromRight 1 (Right 3)
--   3
--   
--   >>> fromRight 1 (Left "foo")
--   1
--

fromRight :: b -> Either a b -> b -- | Reexports Data.Either.Compat from a globally unique namespace. module Data.Either.Compat.Repl module Data.Foldable.Compat -- | Reexports Data.Foldable.Compat from a globally unique -- namespace. module Data.Foldable.Compat.Repl module Data.Function.Compat -- | & is a reverse application operator. This provides -- notational convenience. Its precedence is one higher than that of the -- forward application operator $, which allows & to be -- nested in $. -- --

--   >>> 5 & (+1) & show
--   "6"
--

(&) :: a -> (a -> b) -> b infixl 1 & -- | Reexports Data.Function.Compat from a globally unique -- namespace. module Data.Function.Compat.Repl module Data.Functor.Compat -- | A type f is a Functor if it provides a function fmap -- which, given any types a and b lets you apply any -- function from (a -> b) to turn an f a into an -- f b, preserving the structure of f. Furthermore -- f needs to adhere to the following: -- --

Identity fmap id == id
Composition fmap (f . g) == fmap f . -- fmap g

--   do a <- as
--      pure (f a)
--

--   do bs
--      pure a
--

-- -- with an inferred Functor constraint. (<$) :: Functor f => a -> f b -> f a infixl 4 <$ -- | Flipped version of <$. -- -- Using ApplicativeDo: 'as $> b' can be -- understood as the do expression -- --

--   do as
--      pure b
--

-- -- with an inferred Functor constraint. -- --

Examples

-- -- Replace the contents of a Maybe Int with a -- constant String: -- --

--   >>> Nothing $> "foo"
--   Nothing
--   
--   >>> Just 90210 $> "foo"
--   Just "foo"
--

-- -- Replace the contents of an Either Int -- Int with a constant String, resulting in an -- Either Int String: -- --

--   >>> Left 8675309 $> "foo"
--   Left 8675309
--   
--   >>> Right 8675309 $> "foo"
--   Right "foo"
--

-- -- Replace each element of a list with a constant String: -- --

--   >>> [1,2,3] $> "foo"
--   ["foo","foo","foo"]
--

-- -- Replace the second element of a pair with a constant String: -- --

--   >>> (1,2) $> "foo"
--   (1,"foo")
--

($>) :: Functor f => f a -> b -> f b infixl 4 $> -- | void value discards or ignores the result of -- evaluation, such as the return value of an IO action. -- -- Using ApplicativeDo: 'void as' can be -- understood as the do expression -- --

--   do as
--      pure ()
--

-- -- with an inferred Functor constraint. -- --

Examples

-- -- Replace the contents of a Maybe Int with unit: -- --

--   >>> void Nothing
--   Nothing
--   
--   >>> void (Just 3)
--   Just ()
--

-- -- Replace the contents of an Either Int -- Int with unit, resulting in an Either -- 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
--

void :: Functor f => f a -> f () -- | Flipped version of <$>. -- --

--   (<&>) = flip fmap
--

-- --

Examples

-- -- Apply (+1) to a list, a Just and a Right: -- --

--   >>> Just 2 <&> (+1)
--   Just 3
--

-- --

--   >>> [1,2,3] <&> (+1)
--   [2,3,4]
--

-- --

--   >>> Right 3 <&> (+1)
--   Right 4
--

(<&>) :: Functor f => f a -> (a -> b) -> f b infixl 1 <&> -- | Reexports Data.Functor.Compat from a globally unique namespace. module Data.Functor.Compat.Repl module Data.Functor.Compose.Compat -- | Reexports Data.Functor.Compose.Compat from a globally unique -- namespace. module Data.Functor.Compose.Compat.Repl module Data.Functor.Const.Compat -- | The Const functor. newtype Const a (b :: k) Const :: a -> Const a (b :: k) [getConst] :: Const a (b :: k) -> a -- | Reexports Data.Functor.Const.Compat from a globally unique -- namespace. module Data.Functor.Const.Compat.Repl module Data.Functor.Contravariant.Compat -- | Reexports Data.Functor.Contravariant.Compat from a globally -- unique namespace. module Data.Functor.Contravariant.Compat.Repl module Data.Functor.Identity.Compat -- | Reexports Data.Functor.Identity.Compat from a globally unique -- namespace. module Data.Functor.Identity.Compat.Repl module Data.Functor.Product.Compat -- | Reexports Data.Functor.Product.Compat from a globally unique -- namespace. module Data.Functor.Product.Compat.Repl module Data.Functor.Sum.Compat -- | Reexports Data.Functor.Sum.Compat from a globally unique -- namespace. module Data.Functor.Sum.Compat.Repl module Data.IORef.Compat -- | Strict version of modifyIORef modifyIORef' :: IORef a -> (a -> a) -> IO () -- | Strict version of atomicModifyIORef. This forces both the value -- stored in the IORef and the value returned. The new value is -- installed in the IORef before the returned value is forced. So -- --

--   atomicModifyIORef' ref (x -> (x+1, undefined))
--

-- -- will increment the IORef and then throw an exception in the -- calling thread. atomicModifyIORef' :: IORef a -> (a -> (a, b)) -> IO b -- | Variant of writeIORef with the "barrier to reordering" property -- that atomicModifyIORef has. atomicWriteIORef :: IORef a -> a -> IO () -- | Reexports Data.IORef.Compat from a globally unique namespace. module Data.IORef.Compat.Repl module Data.List.Compat -- | Produce singleton list. -- --

--   >>> singleton True
--   [True]
--

-- -- Since: 4.14.0.0 singleton :: a -> [a] -- | Reexports Data.List.Compat from a globally unique namespace. module Data.List.Compat.Repl -- | This backports the modern Data.Semigroup interface back to -- base-4.9/GHC 8.0. module Data.List.NonEmpty.Compat -- | Non-empty (and non-strict) list type. data NonEmpty a (:|) :: a -> [a] -> NonEmpty a infixr 5 :| -- | Map a function over a NonEmpty stream. map :: (a -> b) -> NonEmpty a -> NonEmpty b -- | 'intersperse x xs' alternates elements of the list with copies of -- x. -- --

--   intersperse 0 (1 :| [2,3]) == 1 :| [0,2,0,3]
--

intersperse :: a -> NonEmpty a -> NonEmpty a -- | scanl is similar to foldl, but returns a stream of -- successive reduced values from the left: -- --

--   scanl f z [x1, x2, ...] == z :| [z `f` x1, (z `f` x1) `f` x2, ...]
--

-- -- Note that -- --

--   last (scanl f z xs) == foldl f z xs.
--

scanl :: Foldable f => (b -> a -> b) -> b -> f a -> NonEmpty b -- | scanr is the right-to-left dual of scanl. Note that -- --

--   head (scanr f z xs) == foldr f z xs.
--

scanr :: Foldable f => (a -> b -> b) -> b -> f a -> NonEmpty b -- | scanl1 is a variant of scanl that has no starting value -- argument: -- --

--   scanl1 f [x1, x2, ...] == x1 :| [x1 `f` x2, x1 `f` (x2 `f` x3), ...]
--

scanl1 :: (a -> a -> a) -> NonEmpty a -> NonEmpty a -- | scanr1 is a variant of scanr that has no starting value -- argument. scanr1 :: (a -> a -> a) -> NonEmpty a -> NonEmpty a -- | transpose for NonEmpty, behaves the same as -- transpose The rows/columns need not be the same length, in -- which case > transpose . transpose /= id transpose :: NonEmpty (NonEmpty a) -> NonEmpty (NonEmpty a) -- | sortBy for NonEmpty, behaves the same as sortBy sortBy :: (a -> a -> Ordering) -> NonEmpty a -> NonEmpty a -- | sortWith for NonEmpty, behaves the same as: -- --

--   sortBy . comparing
--

sortWith :: Ord o => (a -> o) -> NonEmpty a -> NonEmpty a -- | Number of elements in NonEmpty list. length :: NonEmpty a -> Int -- | Extract the first element of the stream. head :: NonEmpty a -> a -- | Extract the possibly-empty tail of the stream. tail :: NonEmpty a -> [a] -- | Extract the last element of the stream. last :: NonEmpty a -> a -- | Extract everything except the last element of the stream. init :: NonEmpty a -> [a] -- | Construct a NonEmpty list from a single element. -- -- Since: 4.15 singleton :: a -> NonEmpty a -- | Prepend an element to the stream. (<|) :: a -> NonEmpty a -> NonEmpty a infixr 5 <| -- | Synonym for <|. cons :: a -> NonEmpty a -> NonEmpty a -- | uncons produces the first element of the stream, and a stream -- of the remaining elements, if any. uncons :: NonEmpty a -> (a, Maybe (NonEmpty a)) -- | The unfoldr function is analogous to Data.List's -- unfoldr operation. unfoldr :: (a -> (b, Maybe a)) -> a -> NonEmpty b -- | Sort a stream. sort :: Ord a => NonEmpty a -> NonEmpty a -- | reverse a finite NonEmpty stream. reverse :: NonEmpty a -> NonEmpty a -- | The inits function takes a stream xs and returns all -- the finite prefixes of xs. inits :: Foldable f => f a -> NonEmpty [a] -- | The tails function takes a stream xs and returns all -- the suffixes of xs. tails :: Foldable f => f a -> NonEmpty [a] -- | iterate f x produces the infinite sequence of repeated -- applications of f to x. -- --

--   iterate f x = x :| [f x, f (f x), ..]
--

iterate :: (a -> a) -> a -> NonEmpty a -- | repeat x returns a constant stream, where all elements -- are equal to x. repeat :: a -> NonEmpty a -- | cycle xs returns the infinite repetition of -- xs: -- --

--   cycle (1 :| [2,3]) = 1 :| [2,3,1,2,3,...]
--

cycle :: NonEmpty a -> NonEmpty a -- | unfold produces a new stream by repeatedly applying the -- unfolding function to the seed value to produce an element of type -- b and a new seed value. When the unfolding function returns -- Nothing instead of a new seed value, the stream ends. unfold :: (a -> (b, Maybe a)) -> a -> NonEmpty b -- | insert x xs inserts x into the last position -- in xs where it is still less than or equal to the next -- element. In particular, if the list is sorted beforehand, the result -- will also be sorted. insert :: (Foldable f, Ord a) => a -> f a -> NonEmpty a -- | some1 x sequences x one or more times. some1 :: Alternative f => f a -> f (NonEmpty a) -- | take n xs returns the first n elements of -- xs. take :: Int -> NonEmpty a -> [a] -- | drop n xs drops the first n elements off the -- front of the sequence xs. drop :: Int -> NonEmpty a -> [a] -- | splitAt n xs returns a pair consisting of the prefix -- of xs of length n and the remaining stream -- immediately following this prefix. -- --

--   'splitAt' n xs == ('take' n xs, 'drop' n xs)
--   xs == ys ++ zs where (ys, zs) = 'splitAt' n xs
--

splitAt :: Int -> NonEmpty a -> ([a], [a]) -- | takeWhile p xs returns the longest prefix of the -- stream xs for which the predicate p holds. takeWhile :: (a -> Bool) -> NonEmpty a -> [a] -- | dropWhile p xs returns the suffix remaining after -- takeWhile p xs. dropWhile :: (a -> Bool) -> NonEmpty a -> [a] -- | span p xs returns the longest prefix of xs -- that satisfies p, together with the remainder of the stream. -- --

--   'span' p xs == ('takeWhile' p xs, 'dropWhile' p xs)
--   xs == ys ++ zs where (ys, zs) = 'span' p xs
--

span :: (a -> Bool) -> NonEmpty a -> ([a], [a]) -- | The break p function is equivalent to span -- (not . p). break :: (a -> Bool) -> NonEmpty a -> ([a], [a]) -- | filter p xs removes any elements from xs that -- do not satisfy p. filter :: (a -> Bool) -> NonEmpty a -> [a] -- | The partition function takes a predicate p and a -- stream xs, and returns a pair of lists. The first list -- corresponds to the elements of xs for which p holds; -- the second corresponds to the elements of xs for which -- p does not hold. -- --

--   'partition' p xs = ('filter' p xs, 'filter' (not . p) xs)
--

partition :: (a -> Bool) -> NonEmpty a -> ([a], [a]) -- | The group function takes a stream and returns a list of streams -- such that flattening the resulting list is equal to the argument. -- Moreover, each stream in the resulting list contains only equal -- elements. For example, in list notation: -- --

--   'group' $ 'cycle' "Mississippi"
--     = "M" : "i" : "ss" : "i" : "ss" : "i" : "pp" : "i" : "M" : "i" : ...
--

group :: (Foldable f, Eq a) => f a -> [NonEmpty a] -- | groupBy operates like group, but uses the provided -- equality predicate instead of ==. groupBy :: Foldable f => (a -> a -> Bool) -> f a -> [NonEmpty a] -- | groupWith operates like group, but uses the provided -- projection when comparing for equality groupWith :: (Foldable f, Eq b) => (a -> b) -> f a -> [NonEmpty a] -- | groupAllWith operates like groupWith, but sorts the list -- first so that each equivalence class has, at most, one list in the -- output groupAllWith :: Ord b => (a -> b) -> [a] -> [NonEmpty a] -- | group1 operates like group, but uses the knowledge that -- its input is non-empty to produce guaranteed non-empty output. group1 :: Eq a => NonEmpty a -> NonEmpty (NonEmpty a) -- | groupBy1 is to group1 as groupBy is to -- group. groupBy1 :: (a -> a -> Bool) -> NonEmpty a -> NonEmpty (NonEmpty a) -- | groupWith1 is to group1 as groupWith is to -- group groupWith1 :: Eq b => (a -> b) -> NonEmpty a -> NonEmpty (NonEmpty a) -- | groupAllWith1 is to groupWith1 as groupAllWith is -- to groupWith groupAllWith1 :: Ord b => (a -> b) -> NonEmpty a -> NonEmpty (NonEmpty a) -- | The isPrefixOf function returns True if the first -- argument is a prefix of the second. isPrefixOf :: Eq a => [a] -> NonEmpty a -> Bool -- | 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 -- inequality test. nub :: Eq a => NonEmpty a -> NonEmpty a -- | The nubBy function behaves just like nub, except it uses -- a user-supplied equality predicate instead of the overloaded == -- function. nubBy :: (a -> a -> Bool) -> NonEmpty a -> NonEmpty a -- | xs !! n returns the element of the stream xs at -- index n. Note that the head of the stream has index 0. -- -- Beware: a negative or out-of-bounds index will cause an error. (!!) :: NonEmpty a -> Int -> a infixl 9 !! -- | The zip function takes two streams and returns a stream of -- corresponding pairs. zip :: NonEmpty a -> NonEmpty b -> NonEmpty (a, b) -- | The zipWith function generalizes zip. Rather than -- tupling the elements, the elements are combined using the function -- passed as the first argument. zipWith :: (a -> b -> c) -> NonEmpty a -> NonEmpty b -> NonEmpty c -- | The unzip function is the inverse of the zip function. unzip :: Functor f => f (a, b) -> (f a, f b) -- | Converts a normal list to a NonEmpty stream. -- -- Raises an error if given an empty list. fromList :: [a] -> NonEmpty a -- | Convert a stream to a normal list efficiently. toList :: NonEmpty a -> [a] -- | nonEmpty efficiently turns a normal list into a NonEmpty -- stream, producing Nothing if the input is empty. nonEmpty :: [a] -> Maybe (NonEmpty a) -- | Compute n-ary logic exclusive OR operation on NonEmpty list. xor :: NonEmpty Bool -> Bool -- | Reexports Data.List.NonEmpty.Compat from a globally unique -- namespace. module Data.List.NonEmpty.Compat.Repl module Data.Monoid.Compat -- | The class of monoids (types with an associative binary operation that -- has an identity). Instances should satisfy the following: -- --

Right identity x <> mempty = -- x
Left identity mempty <> x = -- x
Associativity x <> (y <> z) = -- (x <> y) <> z (Semigroup -- law)
Concatenation 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. class Semigroup a => Monoid a -- | Identity of mappend -- --

--   >>> "Hello world" <> mempty
--   "Hello world"
--

mempty :: Monoid a => a -- | An associative operation -- -- NOTE: This method is redundant and has the default -- implementation mappend = (<>) since -- base-4.11.0.0. Should it be implemented manually, since -- mappend is a synonym for (<>), it is expected that -- the two functions are defined the same way. In a future GHC release -- mappend will be removed from Monoid. mappend :: Monoid a => a -> a -> a -- | 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. -- --

--   >>> mconcat ["Hello", " ", "Haskell", "!"]
--   "Hello Haskell!"
--

mconcat :: Monoid a => [a] -> a -- | Maybe monoid returning the leftmost non-Nothing value. -- -- First a is isomorphic to Alt Maybe -- a, but precedes it historically. -- --

--   >>> getFirst (First (Just "hello") <> First Nothing <> First (Just "world"))
--   Just "hello"
--

-- -- Use of this type is discouraged. Note the following equivalence: -- --

--   Data.Monoid.First x === Maybe (Data.Semigroup.First x)
--

-- -- In addition to being equivalent in the structural sense, the two also -- have Monoid instances that behave the same. This type will be -- marked deprecated in GHC 8.8, and removed in GHC 8.10. Users are -- advised to use the variant from Data.Semigroup and wrap it in -- Maybe. newtype First a First :: Maybe a -> First a [getFirst] :: First a -> Maybe a -- | Maybe monoid returning the rightmost non-Nothing value. -- -- Last a is isomorphic to Dual (First -- a), and thus to Dual (Alt Maybe a) -- --

--   >>> getLast (Last (Just "hello") <> Last Nothing <> Last (Just "world"))
--   Just "world"
--

-- -- Use of this type is discouraged. Note the following equivalence: -- --

--   Data.Monoid.Last x === Maybe (Data.Semigroup.Last x)
--

-- -- In addition to being equivalent in the structural sense, the two also -- have Monoid instances that behave the same. This type will be -- marked deprecated in GHC 8.8, and removed in GHC 8.10. Users are -- advised to use the variant from Data.Semigroup and wrap it in -- Maybe. newtype Last a Last :: Maybe a -> Last a [getLast] :: Last a -> Maybe a -- | This data type witnesses the lifting of a Monoid into an -- Applicative pointwise. newtype Ap (f :: k -> Type) (a :: k) Ap :: f a -> Ap (f :: k -> Type) (a :: k) [getAp] :: Ap (f :: k -> Type) (a :: k) -> f a -- | The dual of a Monoid, obtained by swapping the arguments of -- mappend. -- --

--   >>> getDual (mappend (Dual "Hello") (Dual "World"))
--   "WorldHello"
--

newtype Dual a Dual :: a -> Dual a [getDual] :: Dual a -> a -- | The monoid of endomorphisms under composition. -- --

--   >>> let computation = Endo ("Hello, " ++) <> Endo (++ "!")
--   
--   >>> appEndo computation "Haskell"
--   "Hello, Haskell!"
--

newtype Endo a Endo :: (a -> a) -> Endo a [appEndo] :: Endo a -> a -> a -- | Boolean monoid under conjunction (&&). -- --

--   >>> getAll (All True <> mempty <> All False)
--   False
--

-- --

--   >>> getAll (mconcat (map (\x -> All (even x)) [2,4,6,7,8]))
--   False
--

newtype All All :: Bool -> All [getAll] :: All -> Bool -- | Boolean monoid under disjunction (||). -- --

--   >>> getAny (Any True <> mempty <> Any False)
--   True
--

-- --

--   >>> getAny (mconcat (map (\x -> Any (even x)) [2,4,6,7,8]))
--   True
--

newtype Any Any :: Bool -> Any [getAny] :: Any -> Bool -- | Monoid under addition. -- --

--   >>> getSum (Sum 1 <> Sum 2 <> mempty)
--   3
--

newtype Sum a Sum :: a -> Sum a [getSum] :: Sum a -> a -- | Monoid under multiplication. -- --

--   >>> getProduct (Product 3 <> Product 4 <> mempty)
--   12
--

newtype Product a Product :: a -> Product a [getProduct] :: Product a -> a -- | Monoid under <|>. -- --

--   >>> getAlt (Alt (Just 12) <> Alt (Just 24))
--   Just 12
--

-- --

--   >>> getAlt $ Alt Nothing <> Alt (Just 24)
--   Just 24
--

newtype Alt (f :: k -> Type) (a :: k) Alt :: f a -> Alt (f :: k -> Type) (a :: k) [getAlt] :: Alt (f :: k -> Type) (a :: k) -> f a -- | An associative operation. -- --

--   >>> [1,2,3] <> [4,5,6]
--   [1,2,3,4,5,6]
--

(<>) :: Semigroup a => a -> a -> a infixr 6 <> -- | Reexports Data.Monoid.Compat from a globally unique namespace. module Data.Monoid.Compat.Repl module Data.Proxy.Compat -- | asProxyTypeOf is a type-restricted version of const. It -- is usually used as an infix operator, and its typing forces its first -- argument (which is usually overloaded) to have the same type as the -- tag of the second. -- --

--   >>> import Data.Word
--   
--   >>> :type asProxyTypeOf 123 (Proxy :: Proxy Word8)
--   asProxyTypeOf 123 (Proxy :: Proxy Word8) :: Word8
--

-- -- Note the lower-case proxy in the definition. This allows any -- type constructor with just one argument to be passed to the function, -- for example we could also write -- --

--   >>> import Data.Word
--   
--   >>> :type asProxyTypeOf 123 (Just (undefined :: Word8))
--   asProxyTypeOf 123 (Just (undefined :: Word8)) :: Word8
--

asProxyTypeOf :: a -> proxy a -> a -- | Reexports Data.Proxy.Compat from a globally unique namespace. module Data.Proxy.Compat.Repl module Data.Ratio.Compat -- | Reexports Data.Ratio.Compat from a globally unique namespace. module Data.Ratio.Compat.Repl module Data.STRef.Compat -- | Strict version of modifySTRef modifySTRef' :: STRef s a -> (a -> a) -> ST s () -- | Reexports Data.STRef.Compat from a globally unique namespace. module Data.STRef.Compat.Repl -- | This backports the modern Data.Semigroup interface back to -- base-4.9/GHC 8.0. module Data.Semigroup.Compat -- | The class of semigroups (types with an associative binary operation). -- -- Instances should satisfy the following: -- --

Associativity x <> (y <> z) = -- (x <> y) <> z

class Semigroup a -- | An associative operation. -- --

--   >>> [1,2,3] <> [4,5,6]
--   [1,2,3,4,5,6]
--

(<>) :: Semigroup a => a -> a -> a -- | Reduce a non-empty list with <> -- -- The default definition should be sufficient, but this can be -- overridden for efficiency. -- --

--   >>> import Data.List.NonEmpty
--   
--   >>> sconcat $ "Hello" :| [" ", "Haskell", "!"]
--   "Hello Haskell!"
--

sconcat :: Semigroup a => NonEmpty a -> a -- | Repeat a value n times. -- -- Given that this works on a Semigroup it is allowed to fail if -- you request 0 or fewer repetitions, and the default definition will do -- so. -- -- By making this a member of the class, idempotent semigroups and -- monoids can upgrade this to execute in <math> by picking -- stimes = stimesIdempotent or stimes = -- stimesIdempotentMonoid respectively. -- --

--   >>> stimes 4 [1]
--   [1,1,1,1]
--

stimes :: (Semigroup a, Integral b) => b -> a -> a infixr 6 <> -- | This is a valid definition of stimes for a Monoid. -- -- Unlike the default definition of stimes, it is defined for 0 -- and so it should be preferred where possible. stimesMonoid :: (Integral b, Monoid a) => b -> a -> a -- | This is a valid definition of stimes for an idempotent -- Semigroup. -- -- When x <> x = x, this definition should be preferred, -- because it works in <math> rather than <math>. stimesIdempotent :: Integral b => b -> a -> a -- | This is a valid definition of stimes for an idempotent -- Monoid. -- -- When mappend x x = x, this definition should be preferred, -- because it works in <math> rather than <math> stimesIdempotentMonoid :: (Integral b, Monoid a) => b -> a -> a -- | Repeat a value n times. -- --

--   mtimesDefault n a = a <> a <> ... <> a  -- using <> (n-1) times
--

-- -- Implemented using stimes and mempty. -- -- This is a suitable definition for an mtimes member of -- Monoid. mtimesDefault :: (Integral b, Monoid a) => b -> a -> a newtype Min a Min :: a -> Min a [getMin] :: Min a -> a newtype Max a Max :: a -> Max a [getMax] :: Max a -> a -- | Use Option (First a) to get the behavior of -- First from Data.Monoid. newtype First a First :: a -> First a [getFirst] :: First a -> a -- | Use Option (Last a) to get the behavior of -- Last from Data.Monoid newtype Last a Last :: a -> Last a [getLast] :: Last a -> a -- | Provide a Semigroup for an arbitrary Monoid. -- -- NOTE: This is not needed anymore since Semigroup became -- a superclass of Monoid in base-4.11 and this newtype be -- deprecated at some point in the future. newtype WrappedMonoid m WrapMonoid :: m -> WrappedMonoid m [unwrapMonoid] :: WrappedMonoid m -> m -- | The dual of a Monoid, obtained by swapping the arguments of -- mappend. -- --

--   >>> getDual (mappend (Dual "Hello") (Dual "World"))
--   "WorldHello"
--

newtype Dual a Dual :: a -> Dual a [getDual] :: Dual a -> a -- | The monoid of endomorphisms under composition. -- --

--   >>> let computation = Endo ("Hello, " ++) <> Endo (++ "!")
--   
--   >>> appEndo computation "Haskell"
--   "Hello, Haskell!"
--

newtype Endo a Endo :: (a -> a) -> Endo a [appEndo] :: Endo a -> a -> a -- | Boolean monoid under conjunction (&&). -- --

--   >>> getAll (All True <> mempty <> All False)
--   False
--

-- --

--   >>> getAll (mconcat (map (\x -> All (even x)) [2,4,6,7,8]))
--   False
--

newtype All All :: Bool -> All [getAll] :: All -> Bool -- | Boolean monoid under disjunction (||). -- --

--   >>> getAny (Any True <> mempty <> Any False)
--   True
--

-- --

--   >>> getAny (mconcat (map (\x -> Any (even x)) [2,4,6,7,8]))
--   True
--

newtype Any Any :: Bool -> Any [getAny] :: Any -> Bool -- | Monoid under addition. -- --

--   >>> getSum (Sum 1 <> Sum 2 <> mempty)
--   3
--

newtype Sum a Sum :: a -> Sum a [getSum] :: Sum a -> a -- | Monoid under multiplication. -- --

--   >>> getProduct (Product 3 <> Product 4 <> mempty)
--   12
--

newtype Product a Product :: a -> Product a [getProduct] :: Product a -> a -- | This lets you use a difference list of a Semigroup as a -- Monoid. diff :: Semigroup m => m -> Endo m -- | A generalization of cycle to an arbitrary Semigroup. May -- fail to terminate for some values in some semigroups. cycle1 :: Semigroup m => m -> m -- | Arg isn't itself a Semigroup in its own right, but it -- can be placed inside Min and Max to compute an arg min -- or arg max. data Arg a b Arg :: a -> b -> Arg a b type ArgMin a b = Min Arg a b type ArgMax a b = Max Arg a b -- | Reexports Data.Semigroup.Compat from a globally unique -- namespace. module Data.Semigroup.Compat.Repl module Data.String.Compat -- | A String is a list of characters. String constants in Haskell -- are values of type String. -- -- See Data.List for operations on lists. type String = [Char] -- | lines breaks a string up into a list of strings at newline -- characters. The resulting strings do not contain newlines. -- -- Note that after splitting the string at newline characters, the last -- part of the string is considered a line even if it doesn't end with a -- newline. For example, -- --

--   >>> lines ""
--   []
--

-- --

--   >>> lines "\n"
--   [""]
--

-- --

--   >>> lines "one"
--   ["one"]
--

-- --

--   >>> lines "one\n"
--   ["one"]
--

-- --

--   >>> lines "one\n\n"
--   ["one",""]
--

-- --

--   >>> lines "one\ntwo"
--   ["one","two"]
--

-- --

--   >>> lines "one\ntwo\n"
--   ["one","two"]
--

-- -- Thus lines s contains at least as many elements as -- newlines in s. lines :: String -> [String] -- | words breaks a string up into a list of words, which were -- delimited by white space. -- --

--   >>> words "Lorem ipsum\ndolor"
--   ["Lorem","ipsum","dolor"]
--

words :: String -> [String] -- | unlines is an inverse operation to lines. It joins -- lines, after appending a terminating newline to each. -- --

--   >>> unlines ["Hello", "World", "!"]
--   "Hello\nWorld\n!\n"
--

unlines :: [String] -> String -- | unwords is an inverse operation to words. It joins words -- with separating spaces. -- --

--   >>> unwords ["Lorem", "ipsum", "dolor"]
--   "Lorem ipsum dolor"
--

unwords :: [String] -> String -- | Reexports Data.String.Compat from a globally unique namespace. module Data.String.Compat.Repl module Data.Type.Coercion.Compat -- | Generalized form of type-safe cast using representational equality gcoerceWith :: forall k (a :: k) (b :: k) r. Coercion a b -> (Coercible a b => r) -> r -- | Reexports Data.Type.Coercion.Compat from a globally unique -- namespace. module Data.Type.Coercion.Compat.Repl module Data.Type.Equality.Compat -- | Reexports Data.Type.Equality.Compat from a globally unique -- namespace. module Data.Type.Equality.Compat.Repl module Data.Version.Compat -- | Construct tag-less Version makeVersion :: [Int] -> Version -- | Reexports Data.Version.Compat from a globally unique namespace. module Data.Version.Compat.Repl module Data.Void.Compat -- | Reexports Data.Void.Compat from a globally unique namespace. module Data.Void.Compat.Repl module Data.Word.Compat -- | Reverse order of bytes in Word16. byteSwap16 :: Word16 -> Word16 -- | Reverse order of bytes in Word32. byteSwap32 :: Word32 -> Word32 -- | Reverse order of bytes in Word64. byteSwap64 :: Word64 -> Word64 -- | Reexports Data.Word.Compat from a globally unique namespace. module Data.Word.Compat.Repl module Debug.Trace.Compat -- | Like trace but returns the message instead of a third value. -- --

--   >>> traceId "hello"
--   "hello
--   hello"
--

traceId :: String -> String -- | Like traceShow but returns the shown value instead of a third -- value. -- --

--   >>> traceShowId (1+2+3, "hello" ++ "world")
--   (6,"helloworld")
--   (6,"helloworld")
--

traceShowId :: Show a => a -> a -- | Like trace but returning unit in an arbitrary -- Applicative context. Allows for convenient use in do-notation. -- -- Note that the application of traceM is not an action in the -- Applicative context, as traceIO is in the IO -- type. While the fresh bindings in the following example will force the -- traceM expressions to be reduced every time the -- do-block is executed, traceM "not crashed" would -- only be reduced once, and the message would only be printed once. If -- your monad is in MonadIO, liftIO . -- traceIO may be a better option. -- --

--   >>> :{
--   do
--       x <- Just 3
--       traceM ("x: " ++ show x)
--       y <- pure 12
--       traceM ("y: " ++ show y)
--       pure (x*2 + y)
--   :}
--   x: 3
--   y: 12
--   Just 18
--

traceM :: Applicative f => String -> f () -- | Like traceM, but uses show on the argument to convert it -- to a String. -- --

--   >>> :{
--   do
--       x <- Just 3
--       traceShowM x
--       y <- pure 12
--       traceShowM y
--       pure (x*2 + y)
--   :}
--   3
--   12
--   Just 18
--

traceShowM :: (Show a, Applicative f) => a -> f () -- | Reexports Debug.Trace.Compat from a globally unique namespace. module Debug.Trace.Compat.Repl module Foreign.ForeignPtr.Compat -- | Advances the given address by the given offset in bytes. -- -- The new ForeignPtr shares the finalizer of the original, -- equivalent from a finalization standpoint to just creating another -- reference to the original. That is, the finalizer will not be called -- before the new ForeignPtr is unreachable, nor will it be called -- an additional time due to this call, and the finalizer will be called -- with the same address that it would have had this call not happened, -- *not* the new address. plusForeignPtr :: ForeignPtr a -> Int -> ForeignPtr b -- | Reexports Foreign.ForeignPtr.Compat from a globally unique -- namespace. module Foreign.ForeignPtr.Compat.Repl module Foreign.ForeignPtr.Safe.Compat -- | The type ForeignPtr represents references to objects that are -- maintained in a foreign language, i.e., that are not part of the data -- structures usually managed by the Haskell storage manager. The -- essential difference between ForeignPtrs and vanilla memory -- references of type Ptr a is that the former may be associated -- with finalizers. A finalizer is a routine that is invoked when -- the Haskell storage manager detects that - within the Haskell heap and -- stack - there are no more references left that are pointing to the -- ForeignPtr. Typically, the finalizer will, then, invoke -- routines in the foreign language that free the resources bound by the -- foreign object. -- -- The ForeignPtr is parameterised in the same way as Ptr. -- The type argument of ForeignPtr should normally be an instance -- of class Storable. data ForeignPtr a -- | A finalizer is represented as a pointer to a foreign function that, at -- finalisation time, gets as an argument a plain pointer variant of the -- foreign pointer that the finalizer is associated with. -- -- Note that the foreign function must use the ccall -- calling convention. type FinalizerPtr a = FunPtr Ptr a -> IO () type FinalizerEnvPtr env a = FunPtr Ptr env -> Ptr a -> IO () -- | Turns a plain memory reference into a foreign pointer, and associates -- a finalizer with the reference. The finalizer will be executed after -- the last reference to the foreign object is dropped. There is no -- guarantee of promptness, however the finalizer will be executed before -- the program exits. newForeignPtr :: FinalizerPtr a -> Ptr a -> IO (ForeignPtr a) -- | Turns a plain memory reference into a foreign pointer that may be -- associated with finalizers by using addForeignPtrFinalizer. newForeignPtr_ :: Ptr a -> IO (ForeignPtr a) -- | This function adds a finalizer to the given foreign object. The -- finalizer will run before all other finalizers for the same -- object which have already been registered. addForeignPtrFinalizer :: FinalizerPtr a -> ForeignPtr a -> IO () -- | This variant of newForeignPtr adds a finalizer that expects an -- environment in addition to the finalized pointer. The environment that -- will be passed to the finalizer is fixed by the second argument to -- newForeignPtrEnv. newForeignPtrEnv :: FinalizerEnvPtr env a -> Ptr env -> Ptr a -> IO (ForeignPtr a) -- | Like addForeignPtrFinalizer but the finalizer is passed an -- additional environment parameter. addForeignPtrFinalizerEnv :: FinalizerEnvPtr env a -> Ptr env -> ForeignPtr a -> IO () -- | This is a way to look at the pointer living inside a foreign object. -- This function takes a function which is applied to that pointer. The -- resulting IO action is then executed. The foreign object is -- kept alive at least during the whole action, even if it is not used -- directly inside. Note that it is not safe to return the pointer from -- the action and use it after the action completes. All uses of the -- pointer should be inside the withForeignPtr bracket. The reason -- for this unsafeness is the same as for unsafeForeignPtrToPtr -- below: the finalizer may run earlier than expected, because the -- compiler can only track usage of the ForeignPtr object, not a -- Ptr object made from it. -- -- This function is normally used for marshalling data to or from the -- object pointed to by the ForeignPtr, using the operations from -- the Storable class. withForeignPtr :: ForeignPtr a -> (Ptr a -> IO b) -> IO b -- | Causes the finalizers associated with a foreign pointer to be run -- immediately. finalizeForeignPtr :: ForeignPtr a -> IO () -- | This function ensures that the foreign object in question is alive at -- the given place in the sequence of IO actions. In particular -- withForeignPtr does a touchForeignPtr after it executes -- the user action. -- -- Note that this function should not be used to express dependencies -- between finalizers on ForeignPtrs. For example, if the -- finalizer for a ForeignPtr F1 calls -- touchForeignPtr on a second ForeignPtr F2, then -- the only guarantee is that the finalizer for F2 is never -- started before the finalizer for F1. They might be started -- together if for example both F1 and F2 are otherwise -- unreachable, and in that case the scheduler might end up running the -- finalizer for F2 first. -- -- In general, it is not recommended to use finalizers on separate -- objects with ordering constraints between them. To express the -- ordering robustly requires explicit synchronisation using -- MVars between the finalizers, but even then the runtime -- sometimes runs multiple finalizers sequentially in a single thread -- (for performance reasons), so synchronisation between finalizers could -- result in artificial deadlock. Another alternative is to use explicit -- reference counting. touchForeignPtr :: ForeignPtr a -> IO () -- | This function casts a ForeignPtr parameterised by one type into -- another type. castForeignPtr :: ForeignPtr a -> ForeignPtr b -- | Allocate some memory and return a ForeignPtr to it. The memory -- will be released automatically when the ForeignPtr is -- discarded. -- -- mallocForeignPtr is equivalent to -- --

--   do { p <- malloc; newForeignPtr finalizerFree p }
--

-- -- although it may be implemented differently internally: you may not -- assume that the memory returned by mallocForeignPtr has been -- allocated with malloc. -- -- GHC notes: mallocForeignPtr has a heavily optimised -- implementation in GHC. It uses pinned memory in the garbage collected -- heap, so the ForeignPtr does not require a finalizer to free -- the memory. Use of mallocForeignPtr and associated functions is -- strongly recommended in preference to newForeignPtr with a -- finalizer. mallocForeignPtr :: Storable a => IO (ForeignPtr a) -- | This function is similar to mallocForeignPtr, except that the -- size of the memory required is given explicitly as a number of bytes. mallocForeignPtrBytes :: Int -> IO (ForeignPtr a) -- | This function is similar to mallocArray, but yields a memory -- area that has a finalizer attached that releases the memory area. As -- with mallocForeignPtr, it is not guaranteed that the block of -- memory was allocated by malloc. mallocForeignPtrArray :: Storable a => Int -> IO (ForeignPtr a) -- | This function is similar to mallocArray0, but yields a memory -- area that has a finalizer attached that releases the memory area. As -- with mallocForeignPtr, it is not guaranteed that the block of -- memory was allocated by malloc. mallocForeignPtrArray0 :: Storable a => Int -> IO (ForeignPtr a) -- | Reexports Foreign.ForeignPtr.Safe.Compat from a globally unique -- namespace. module Foreign.ForeignPtr.Safe.Compat.Repl module Foreign.ForeignPtr.Unsafe.Compat -- | This function extracts the pointer component of a foreign pointer. -- This is a potentially dangerous operations, as if the argument to -- unsafeForeignPtrToPtr is the last usage occurrence of the given -- foreign pointer, then its finalizer(s) will be run, which potentially -- invalidates the plain pointer just obtained. Hence, -- touchForeignPtr must be used wherever it has to be guaranteed -- that the pointer lives on - i.e., has another usage occurrence. -- -- To avoid subtle coding errors, hand written marshalling code should -- preferably use withForeignPtr rather than combinations of -- unsafeForeignPtrToPtr and touchForeignPtr. However, the -- latter routines are occasionally preferred in tool generated -- marshalling code. unsafeForeignPtrToPtr :: ForeignPtr a -> Ptr a -- | Reexports Foreign.ForeignPtr.Unsafe.Compat from a globally -- unique namespace. module Foreign.ForeignPtr.Unsafe.Compat.Repl module Foreign.Marshal.Alloc.Compat -- | Like malloc but memory is filled with bytes of value zero. calloc :: Storable a => IO (Ptr a) -- | Llike mallocBytes but memory is filled with bytes of value -- zero. callocBytes :: Int -> IO (Ptr a) -- | Reexports Foreign.Marshal.Alloc.Compat from a globally unique -- namespace. module Foreign.Marshal.Alloc.Compat.Repl module Foreign.Marshal.Array.Compat -- | Like mallocArray, but allocated memory is filled with bytes of -- value zero. callocArray :: Storable a => Int -> IO (Ptr a) -- | Like callocArray0, but allocated memory is filled with bytes of -- value zero. callocArray0 :: Storable a => Int -> IO (Ptr a) -- | Reexports Foreign.Marshal.Array.Compat from a globally unique -- namespace. module Foreign.Marshal.Array.Compat.Repl module Foreign.Marshal.Safe.Compat -- | Reexports Foreign.Marshal.Safe.Compat from a globally unique -- namespace. module Foreign.Marshal.Safe.Compat.Repl module Foreign.Marshal.Unsafe.Compat -- | Sometimes an external entity is a pure function, except that it passes -- arguments and/or results via pointers. The function -- unsafeLocalState permits the packaging of such entities as -- pure functions. -- -- The only IO operations allowed in the IO action passed to -- unsafeLocalState are (a) local allocation (alloca, -- allocaBytes and derived operations such as withArray -- and withCString), and (b) pointer operations -- (Foreign.Storable and Foreign.Ptr) on the pointers -- to local storage, and (c) foreign functions whose only observable -- effect is to read and/or write the locally allocated memory. Passing -- an IO operation that does not obey these rules results in undefined -- behaviour. -- -- It is expected that this operation will be replaced in a future -- revision of Haskell. unsafeLocalState :: IO a -> a -- | Reexports Foreign.Marshal.Unsafe.Compat from a globally unique -- namespace. module Foreign.Marshal.Unsafe.Compat.Repl module Foreign.Marshal.Utils.Compat -- | Fill a given number of bytes in memory area with a byte value. fillBytes :: Ptr a -> Word8 -> Int -> IO () module Foreign.Marshal.Compat -- | Reexports Foreign.Marshal.Compat from a globally unique -- namespace. module Foreign.Marshal.Compat.Repl module Foreign.Compat -- | Reexports Foreign.Compat from a globally unique namespace. module Foreign.Compat.Repl -- | Reexports Foreign.Marshal.Utils.Compat from a globally unique -- namespace. module Foreign.Marshal.Utils.Compat.Repl module Numeric.Natural.Compat -- | Reexports Numeric.Natural.Compat from a globally unique -- namespace. module Numeric.Natural.Compat.Repl module Prelude.Compat -- | Reexports Prelude.Compat from a globally unique namespace. module Prelude.Compat.Repl -- | Miscellaneous information about the system environment. module System.Environment.Compat -- | Computation getArgs returns a list of the program's command -- line arguments (not including the program name). getArgs :: IO [String] -- | Computation getProgName returns the name of the program as it -- was invoked. -- -- However, this is hard-to-impossible to implement on some non-Unix -- OSes, so instead, for maximum portability, we just return the leafname -- of the program as invoked. Even then there are some differences -- between platforms: on Windows, for example, a program invoked as foo -- is probably really FOO.EXE, and that is what -- getProgName will return. getProgName :: IO String -- | Computation getEnv var returns the value of the -- environment variable var. For the inverse, the setEnv -- function can be used. -- -- This computation may fail with: -- --

isDoesNotExistError if the environment variable does not -- exist.

getEnv :: String -> IO String -- | Return the value of the environment variable var, or -- Nothing if there is no such value. -- -- For POSIX users, this is equivalent to getEnv. lookupEnv :: String -> IO (Maybe String) -- | setEnv name value sets the specified environment variable to -- value. -- -- Early versions of this function operated under the mistaken belief -- that setting an environment variable to the empty string on -- Windows removes that environment variable from the environment. For -- the sake of compatibility, it adopted that behavior on POSIX. In -- particular -- --

--   setEnv name ""
--

-- -- has the same effect as -- --

--   unsetEnv name
--

-- -- If you'd like to be able to set environment variables to blank -- strings, use setEnv. -- -- Throws IOException if name is the empty string or -- contains an equals sign. setEnv :: String -> String -> IO () -- | unsetEnv name removes the specified environment variable from -- the environment of the current process. -- -- Throws IOException if name is the empty string or -- contains an equals sign. unsetEnv :: String -> IO () -- | withArgs args act - while executing action -- act, have getArgs return args. withArgs :: [String] -> IO a -> IO a -- | withProgName name act - while executing action -- act, have getProgName return name. withProgName :: String -> IO a -> IO a -- | getEnvironment retrieves the entire environment as a list of -- (key,value) pairs. -- -- If an environment entry does not contain an '=' character, -- the key is the whole entry and the value is the -- empty string. getEnvironment :: IO [(String, String)] -- | Reexports System.Environment.Compat from a globally unique -- namespace. module System.Environment.Compat.Repl module System.Exit.Compat -- | Write given error message to stderr and terminate with -- exitFailure. die :: String -> IO a -- | Reexports System.Exit.Compat from a globally unique namespace. module System.Exit.Compat.Repl module System.IO.Compat -- | The getContents' operation returns all user input as a single -- string, which is fully read before being returned (same as -- hGetContents' stdin). -- -- Since: 4.15.0.0 getContents' :: IO String -- | The hGetContents' operation reads all input on the given handle -- before returning it as a String and closing the handle. -- -- Since: 4.15.0.0 hGetContents' :: Handle -> IO String -- | The readFile' function reads a file and returns the contents of -- the file as a string. The file is fully read before being returned, as -- with getContents'. -- -- Since: 4.15.0.0 readFile' :: FilePath -> IO String -- | Reexports System.IO.Compat from a globally unique namespace. module System.IO.Compat.Repl module System.IO.Error.Compat -- | An error indicating that the operation failed because the resource -- vanished. See resourceVanishedErrorType. isResourceVanishedError :: IOError -> Bool -- | I/O error where the operation failed because the resource vanished. -- This happens when, for example, attempting to write to a closed socket -- or attempting to write to a named pipe that was deleted. resourceVanishedErrorType :: IOErrorType -- | I/O error where the operation failed because the resource vanished. -- See resourceVanishedErrorType. isResourceVanishedErrorType :: IOErrorType -> Bool -- | Reexports System.IO.Error.Compat from a globally unique -- namespace. module System.IO.Error.Compat.Repl module System.IO.Unsafe.Compat -- | A slightly faster version of fixIO that may not be safe to use -- with multiple threads. The unsafety arises when used like this: -- --

--   unsafeFixIO $ \r -> do
--      forkIO (print r)
--      return (...)
--

-- -- In this case, the child thread will receive a NonTermination -- exception instead of waiting for the value of r to be -- computed. unsafeFixIO :: (a -> IO a) -> IO a -- | This version of unsafePerformIO is more efficient because it -- omits the check that the IO is only being performed by a single -- thread. Hence, when you use unsafeDupablePerformIO, there is a -- possibility that the IO action may be performed multiple times (on a -- multiprocessor), and you should therefore ensure that it gives the -- same results each time. It may even happen that one of the duplicated -- IO actions is only run partially, and then interrupted in the middle -- without an exception being raised. Therefore, functions like -- bracket cannot be used safely within -- unsafeDupablePerformIO. unsafeDupablePerformIO :: IO a -> a -- | Reexports System.IO.Unsafe.Compat from a globally unique -- namespace. module System.IO.Unsafe.Compat.Repl module Text.Read.Compat -- | 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 Read instance 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 -- Read will parse only the record-syntax form, and furthermore, -- the fields must be given in the same order as the original -- declaration.
The derived Read instance 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 = 5
--

-- -- Note 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 = readListPrecDefault
--

-- -- Why 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: -- --

--   instance Read T where
--     readPrec     = ...
--     readListPrec = readListPrecDefault
--

class Read 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: -- --

(x,"") is an element of (readsPrec d -- (showsPrec d x "")).

-- -- That is, readsPrec parses the string produced by -- showsPrec, and delivers the value that showsPrec started -- with. readsPrec :: Read a => Int -> ReadS a -- | The method readList is provided to allow the programmer to give -- a specialised way of parsing lists of values. For example, this is -- used by the predefined Read instance of the Char type, -- where values of type String should be are expected to use -- double quotes, rather than square brackets. readList :: Read a => ReadS [a] -- | Proposed replacement for readsPrec using new-style parsers (GHC -- only). readPrec :: Read a => ReadPrec a -- | Proposed replacement for readList using new-style parsers (GHC -- only). The default definition uses readList. Instances that -- define readPrec should also define readListPrec as -- readListPrecDefault. readListPrec :: Read a => ReadPrec [a] -- | A parser for a type a, represented as a function that takes a -- String and returns a list of possible parses as -- (a,String) pairs. -- -- Note that this kind of backtracking parser is very inefficient; -- reading a large structure may be quite slow (cf ReadP). type ReadS a = String -> [(a, String)] -- | equivalent to readsPrec with a precedence of 0. reads :: Read a => ReadS a -- | The read function reads input from a string, which must be -- completely consumed by the input process. read fails with an -- error if the parse is unsuccessful, and it is therefore -- discouraged from being used in real applications. Use readMaybe -- or readEither for safe alternatives. -- --

--   >>> read "123" :: Int
--   123
--

-- --

--   >>> read "hello" :: Int
--   *** Exception: Prelude.read: no parse
--

read :: Read a => String -> a -- | readParen True p parses what p parses, -- but surrounded with parentheses. -- -- readParen False p parses what p -- parses, but optionally surrounded with parentheses. readParen :: Bool -> ReadS a -> ReadS a -- | 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 "" = [("","")].) If there is -- no legal lexeme at the beginning of the input string, 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

lex :: ReadS String data Lexeme -- | Character literal Char :: Char -> Lexeme -- | String literal, with escapes interpreted String :: String -> Lexeme -- | Punctuation or reserved symbol, e.g. (, :: Punc :: String -> Lexeme -- | Haskell identifier, e.g. foo, Baz Ident :: String -> Lexeme -- | Haskell symbol, e.g. >>, :% Symbol :: String -> Lexeme Number :: Number -> Lexeme EOF :: Lexeme -- | Parse a single lexeme lexP :: ReadPrec Lexeme -- | (parens p) parses "P", "(P0)", "((P0))", etc, where -- p parses "P" in the current precedence context and parses -- "P0" in precedence context zero parens :: ReadPrec a -> ReadPrec a -- | A possible replacement definition for the readList method (GHC -- only). This is only needed for GHC, and even then only for Read -- instances where readListPrec isn't defined as -- readListPrecDefault. readListDefault :: Read a => ReadS [a] -- | A possible replacement definition for the readListPrec method, -- defined using readPrec (GHC only). readListPrecDefault :: Read a => ReadPrec [a] -- | Parse a string using the Read instance. Succeeds if there is -- exactly one valid result. A Left value indicates a parse error. -- --

--   >>> readEither "123" :: Either String Int
--   Right 123
--

-- --

--   >>> readEither "hello" :: Either String Int
--   Left "Prelude.read: no parse"
--

readEither :: Read a => String -> Either String a -- | Parse a string using the Read instance. Succeeds if there is -- exactly one valid result. -- --

--   >>> readMaybe "123" :: Maybe Int
--   Just 123
--

-- --

--   >>> readMaybe "hello" :: Maybe Int
--   Nothing
--

readMaybe :: Read a => String -> Maybe a -- | Reexports Text.Read.Compat from a globally unique namespace. module Text.Read.Compat.Repl module Text.Read.Lex.Compat readBinP :: (Eq a, Num a) => ReadP a module Numeric.Compat -- | Show non-negative Integral numbers in base 2. showBin :: (Integral a, Show a) => a -> ShowS -- | Show a signed RealFloat value using standard decimal notation -- (e.g. 245000, 0.0015). -- -- This behaves as showFFloat, except that a decimal point is -- always guaranteed, even if not needed. showFFloatAlt :: RealFloat a => Maybe Int -> a -> ShowS -- | Show a signed RealFloat value using standard decimal notation -- for arguments whose absolute value lies between 0.1 and -- 9,999,999, and scientific notation otherwise. -- -- This behaves as showFFloat, except that a decimal point is -- always guaranteed, even if not needed. showGFloatAlt :: RealFloat a => Maybe Int -> a -> ShowS -- | Show a floating-point value in the hexadecimal format, similar to the -- %a specifier in C's printf. -- --

--   >>> showHFloat (212.21 :: Double) ""
--   "0x1.a86b851eb851fp7"
--   
--   >>> showHFloat (-12.76 :: Float) ""
--   "-0x1.9851ecp3"
--   
--   >>> showHFloat (-0 :: Double) ""
--   "-0x0p+0"
--

showHFloat :: RealFloat a => a -> ShowS -- | Read an unsigned number in binary notation. -- --

--   >>> readBin "10011"
--   [(19,"")]
--

readBin :: (Eq a, Num a) => ReadS a -- | Reexports Numeric.Compat from a globally unique namespace. module Numeric.Compat.Repl -- | Reexports Text.Read.Lex.Compat from a globally unique -- namespace. module Text.Read.Lex.Compat.Repl module Type.Reflection.Compat -- | Use a TypeRep as Typeable evidence. withTypeable :: forall k (a :: k) (rep :: RuntimeRep) (r :: TYPE rep). TypeRep a -> (Typeable a => r) -> r -- | Reexports Type.Reflection.Compat from a globally unique -- namespace. module Type.Reflection.Compat.Repl