-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/
-- | An enhanced core prelude; a common foundation for alternate preludes.
--
-- The premise of basic-prelude is that there are a lot of very
-- commonly desired features missing from the standard Prelude,
-- such as commonly used operators (<$> and
-- >=>, for instance) and imports for common datatypes
-- (e.g., ByteString and Vector). At the same time,
-- there are lots of other components which are more debatable, such as
-- providing polymorphic versions of common functions.
--
-- So basic-prelude is intended to give a common foundation for
-- a number of alternate preludes. The package provides two modules:
-- CorePrelude provides the common ground for other preludes to
-- build on top of, while BasicPrelude exports
-- CorePrelude together with commonly used list functions to
-- provide a drop-in replacement for the standard Prelude.
--
-- Users wishing to have an improved Prelude can use
-- BasicPrelude. Developers wishing to create a new prelude
-- should use CorePrelude.
--
-- Release history:
--
--
-- - 0.3 Moved a number of exports from BasicPrelude to
-- CorePrelude and vice-versa.
-- - 0.2 Renamed BasicPrelude to CorePrelude
-- and added a new BasicPrelude module provided a full-featured
-- Prelude alternative. Also added a number of new exports.
-- - 0.1 Initial version, code taken from
-- classy-prelude with a few minor tweaks.
--
@package basic-prelude
@version 0.3.4.0
module CorePrelude
-- | Application operator. This operator is redundant, since ordinary
-- application (f x) means the same as (f $ x).
-- However, $ 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) xs, or zipWith ($) fs xs.
($) :: (a -> b) -> a -> b
-- | Strict (call-by-value) application, defined in terms of seq.
($!) :: (a -> b) -> a -> b
-- | Boolean "and"
(&&) :: Bool -> Bool -> Bool
-- | Boolean "or"
(||) :: Bool -> Bool -> Bool
-- | morphism composition
(.) :: Category cat => forall b c a. cat b c -> cat a b -> cat a c
-- | Boolean "not"
not :: Bool -> Bool
-- | otherwise is defined as the value True. It helps to make
-- guards more readable. eg.
--
--
-- f x | x < 0 = ...
-- | otherwise = ...
--
otherwise :: Bool
-- | Extract the first component of a pair.
fst :: (a, b) -> a
-- | Extract the second component of a pair.
snd :: (a, b) -> b
-- | the identity morphism
id :: Category cat => forall a. cat a a
-- | 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.
maybe :: b -> (a -> b) -> Maybe a -> b
-- | Case analysis for the Either type. If the value is
-- Left a, apply the first function to a; if it
-- is Right b, apply the second function to b.
either :: (a -> c) -> (b -> c) -> Either a b -> c
-- | flip f takes its (first) two arguments in the reverse
-- order of f.
flip :: (a -> b -> c) -> b -> a -> c
-- | Constant function.
const :: a -> b -> a
-- | error stops execution and displays an error message.
error :: [Char] -> a
putStrLn :: MonadIO m => Text -> m ()
getArgs :: MonadIO m => m [Text]
odd :: Integral a => a -> Bool
even :: Integral a => a -> Bool
-- | uncurry converts a curried function to a function on pairs.
uncurry :: (a -> b -> c) -> (a, b) -> c
-- | curry converts an uncurried function to a curried function.
curry :: ((a, b) -> c) -> a -> b -> c
-- | Swap the components of a pair.
swap :: (a, b) -> (b, a)
-- | until p f yields the result of applying f
-- until p holds.
until :: (a -> Bool) -> (a -> a) -> a -> a
-- | asTypeOf 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
-- second.
asTypeOf :: a -> a -> a
-- | A special case of error. It is expected that compilers will
-- recognize this and insert error messages which are more appropriate to
-- the context in which undefined appears.
undefined :: a
-- | Evaluates its first argument to head normal form, and then returns its
-- second argument as the result.
seq :: a -> b -> b
-- | 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.
class Eq a => Ord a
compare :: Ord a => a -> a -> Ordering
(<) :: Ord a => a -> a -> Bool
(>=) :: Ord a => a -> a -> Bool
(>) :: Ord a => a -> a -> Bool
(<=) :: Ord a => a -> a -> Bool
max :: Ord a => a -> a -> a
min :: Ord a => a -> a -> a
-- | 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.
--
-- Minimal complete definition: either == or /=.
class Eq a
(==) :: Eq a => a -> a -> Bool
(/=) :: Eq a => a -> a -> Bool
-- | 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.
class Bounded a
minBound :: Bounded a => a
maxBound :: Bounded a => a
-- | 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:
--
--
--
--
-- enumFrom x = enumFromTo x maxBound
-- enumFromThen x y = enumFromThenTo x y bound
-- where
-- bound | fromEnum y >= fromEnum x = maxBound
-- | otherwise = minBound
--
class Enum a
succ :: Enum a => a -> a
pred :: Enum a => a -> a
toEnum :: Enum a => Int -> a
fromEnum :: Enum a => a -> Int
enumFrom :: Enum a => a -> [a]
enumFromThen :: Enum a => a -> a -> [a]
enumFromTo :: Enum a => a -> a -> [a]
enumFromThenTo :: Enum a => a -> a -> a -> [a]
-- | Conversion of values to readable Strings.
--
-- Minimal complete definition: showsPrec or show.
--
-- Derived instances of Show have the following properties, which
-- are compatible with derived instances of Read:
--
--
-- - The result of show is 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
-- showsPrec will produce infix applications of the
-- constructor.
-- - the representation will be enclosed in parentheses if the
-- precedence of the top-level constructor in x is less than
-- d (associativity is ignored). Thus, if d is
-- 0 then the result is never surrounded in parentheses; if
-- d is 11 it is always surrounded in parentheses,
-- unless it is an atomic expression.
-- - If the constructor is defined using record syntax, then
-- show will 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 = 5
--
--
-- Note that right-associativity of :^: is ignored. For example,
--
--
-- - show (Leaf 1 :^: Leaf 2 :^: Leaf 3) produces the
-- string "Leaf 1 :^: (Leaf 2 :^: Leaf 3)".
--
class Show a
-- | Parsing of Strings, producing values.
--
-- Minimal complete definition: readsPrec (or, for GHC only,
-- readPrec)
--
-- 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 98 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
--
class Read a
-- | 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.
class Functor (f :: * -> *)
fmap :: Functor f => (a -> b) -> f a -> f b
(<$) :: Functor f => a -> f b -> f 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.
--
-- Minimal complete definition: >>= and return.
--
-- Instances of Monad should satisfy the following laws:
--
--
-- return a >>= k == k a
-- m >>= return == m
-- m >>= (\x -> k x >>= h) == (m >>= k) >>= h
--
--
-- Instances of both Monad and Functor should additionally
-- satisfy the law:
--
--
-- fmap f xs == xs >>= return . f
--
--
-- The instances of Monad for lists, Maybe and IO
-- defined in the Prelude satisfy these laws.
class Monad (m :: * -> *)
(>>=) :: Monad m => m a -> (a -> m b) -> m b
(>>) :: Monad m => m a -> m b -> m b
return :: Monad m => a -> m a
fail :: Monad m => String -> m a
-- | Same as >>=, but with the arguments interchanged.
(=<<) :: Monad m => (a -> m b) -> m a -> m b
-- | Class for string-like datastructures; used by the overloaded string
-- extension (-foverloaded-strings in GHC).
class IsString a
fromString :: IsString a => String -> a
-- | Basic numeric class.
--
-- Minimal complete definition: all except negate or (-)
class Num a
(+) :: Num a => a -> a -> a
(*) :: Num a => a -> a -> a
(-) :: Num a => a -> a -> a
negate :: Num a => a -> a
abs :: Num a => a -> a
signum :: Num a => a -> a
fromInteger :: Num a => Integer -> a
class (Num a, Ord a) => Real a
toRational :: Real a => a -> Rational
-- | Integral numbers, supporting integer division.
--
-- Minimal complete definition: quotRem and toInteger
class (Real a, Enum a) => Integral a
quot :: Integral a => a -> a -> a
rem :: Integral a => a -> a -> a
div :: Integral a => a -> a -> a
mod :: Integral a => a -> a -> a
quotRem :: Integral a => a -> a -> (a, a)
divMod :: Integral a => a -> a -> (a, a)
toInteger :: Integral a => a -> Integer
-- | Fractional numbers, supporting real division.
--
-- Minimal complete definition: fromRational and (recip or
-- (/))
class Num a => Fractional a
(/) :: Fractional a => a -> a -> a
recip :: Fractional a => a -> a
fromRational :: Fractional a => Rational -> a
-- | Trigonometric and hyperbolic functions and related functions.
--
-- Minimal complete definition: pi, exp, log,
-- sin, cos, sinh, cosh, asin,
-- acos, atan, asinh, acosh and atanh
class Fractional a => Floating a
pi :: Floating a => a
exp :: Floating a => a -> a
sqrt :: Floating a => a -> a
log :: Floating a => a -> a
(**) :: Floating a => a -> a -> a
logBase :: Floating a => a -> a -> a
sin :: Floating a => a -> a
tan :: Floating a => a -> a
cos :: Floating a => a -> a
asin :: Floating a => a -> a
atan :: Floating a => a -> a
acos :: Floating a => a -> a
sinh :: Floating a => a -> a
tanh :: Floating a => a -> a
cosh :: Floating a => a -> a
asinh :: Floating a => a -> a
atanh :: Floating a => a -> a
acosh :: Floating a => a -> a
-- | Extracting components of fractions.
--
-- Minimal complete definition: properFraction
class (Real a, Fractional a) => RealFrac a
properFraction :: (RealFrac a, Integral b) => a -> (b, a)
truncate :: (RealFrac a, Integral b) => a -> b
round :: (RealFrac a, Integral b) => a -> b
ceiling :: (RealFrac a, Integral b) => a -> b
floor :: (RealFrac a, Integral b) => a -> b
-- | Efficient, machine-independent access to the components of a
-- floating-point number.
--
-- Minimal complete definition: all except exponent,
-- significand, scaleFloat and atan2
class (RealFrac a, Floating a) => RealFloat a
floatRadix :: RealFloat a => a -> Integer
floatDigits :: RealFloat a => a -> Int
floatRange :: RealFloat a => a -> (Int, Int)
decodeFloat :: RealFloat a => a -> (Integer, Int)
encodeFloat :: RealFloat a => Integer -> Int -> a
exponent :: RealFloat a => a -> Int
significand :: RealFloat a => a -> a
scaleFloat :: RealFloat a => Int -> a -> a
isNaN :: RealFloat a => a -> Bool
isInfinite :: RealFloat a => a -> Bool
isDenormalized :: RealFloat a => a -> Bool
isNegativeZero :: RealFloat a => a -> Bool
isIEEE :: RealFloat a => a -> Bool
atan2 :: RealFloat a => a -> a -> a
-- | The Maybe type encapsulates an optional value. A value of type
-- Maybe a either contains a value of type a
-- (represented as Just a), or it is empty (represented
-- as Nothing). 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.
data Maybe a :: * -> *
Nothing :: Maybe a
Just :: a -> Maybe a
data Ordering :: *
LT :: Ordering
EQ :: Ordering
GT :: Ordering
data Bool :: *
False :: Bool
True :: Bool
-- | The character type Char is an enumeration whose values
-- represent Unicode (or equivalently ISO/IEC 10646) 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).
data Char :: *
-- | A value of type IO a is a computation which, when
-- performed, does some I/O before returning a value of type a.
--
-- 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.
data IO a :: * -> *
-- | The Either type represents values with two possibilities: a
-- value of type Either a b is either Left
-- a or Right 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").
data Either a b :: * -> * -> *
Left :: a -> Either a b
Right :: b -> Either a b
-- | A space-efficient representation of a Word8 vector, supporting many
-- efficient operations. A ByteString contains 8-bit characters
-- only.
--
-- Instances of Eq, Ord, Read, Show, Data, Typeable
data ByteString :: *
type LByteString = ByteString
-- | A space efficient, packed, unboxed Unicode text type.
data Text :: *
type LText = Text
-- | A Map from keys k to values a.
data Map k a :: * -> * -> *
-- | A map from keys to values. A map cannot contain duplicate keys; each
-- key can map to at most one value.
data HashMap k v :: * -> * -> *
-- | A set of values a.
data Set a :: * -> *
-- | A set of values. A set cannot contain duplicate values.
data HashSet a :: * -> *
-- | General-purpose finite sequences.
data Seq a :: * -> *
-- | Boxed vectors, supporting efficient slicing.
data Vector a :: * -> *
type UVector = Vector
class (Vector Vector a, MVector MVector a) => Unbox a
-- | The class of types that can be converted to a hash value.
class Hashable a
hashWithSalt :: Hashable a => Int -> a -> Int
-- | A Word is an unsigned integral type, with the same size as
-- Int.
data Word :: *
-- | 8-bit unsigned integer type
data Word8 :: *
-- | 32-bit unsigned integer type
data Word32 :: *
-- | 64-bit unsigned integer type
data Word64 :: *
-- | 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.
data Int :: *
-- | 32-bit signed integer type
data Int32 :: *
-- | 64-bit signed integer type
data Int64 :: *
-- | Arbitrary-precision integers.
data Integer :: *
-- | Arbitrary-precision rational numbers, represented as a ratio of two
-- Integer values. A rational number may be constructed using the
-- % operator.
type Rational = Ratio Integer
-- | 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.
data Float :: *
-- | 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.
data Double :: *
-- | raise a number to a non-negative integral power
(^) :: (Num a, Integral b) => a -> b -> a
-- | raise a number to an integral power
(^^) :: (Fractional a, Integral b) => a -> b -> a
-- | the same as flip (-).
--
-- Because - is treated specially in the Haskell grammar,
-- (- e) is not a section, but an application of
-- prefix negation. However, (subtract
-- exp) is equivalent to the disallowed section.
subtract :: Num a => a -> a -> a
-- | general coercion from integral types
fromIntegral :: (Integral a, Num b) => a -> b
-- | general coercion to fractional types
realToFrac :: (Real a, Fractional b) => a -> b
-- | The class of monoids (types with an associative binary operation that
-- has an identity). Instances should satisfy the following laws:
--
--
--
-- The method names refer to the monoid of lists under concatenation, but
-- there are many other instances.
--
-- Minimal complete definition: mempty and mappend.
--
-- 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.
class Monoid a
mempty :: Monoid a => a
mappend :: Monoid a => a -> a -> a
mconcat :: Monoid a => [a] -> a
-- | An infix synonym for mappend.
(<>) :: Monoid m => m -> m -> m
-- | Send the first component of the input through the argument arrow, and
-- copy the rest unchanged to the output.
first :: Arrow a => forall b c d. a b c -> a (b, d) (c, d)
-- | A mirror image of first.
--
-- The default definition may be overridden with a more efficient version
-- if desired.
second :: Arrow a => forall b c d. a b c -> a (d, b) (d, c)
-- | 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 => forall b c b' c'. a b c -> a b' c' -> a (b, b') (c, c')
-- | 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.
(&&&) :: Arrow a => forall b c c'. a b c -> a b c' -> a b (c, c')
-- | The mapMaybe function is a version of map which can
-- throw out elements. In particular, the functional argument returns
-- something of type Maybe b. If this is Nothing,
-- no element is added on to the result list. If it just Just
-- b, then b is included in the result list.
mapMaybe :: (a -> Maybe b) -> [a] -> [b]
-- | The catMaybes function takes a list of Maybes and
-- returns a list of all the Just values.
catMaybes :: [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.
fromMaybe :: a -> Maybe a -> a
-- | The isJust function returns True iff its argument is of
-- the form Just _.
isJust :: Maybe a -> Bool
-- | The isNothing function returns True iff its argument is
-- Nothing.
isNothing :: Maybe a -> Bool
-- | The listToMaybe function returns Nothing on an empty
-- list or Just a where a is the first element
-- of the list.
listToMaybe :: [a] -> Maybe a
-- | The maybeToList function returns an empty list when given
-- Nothing or a singleton list when not given Nothing.
maybeToList :: Maybe a -> [a]
-- | 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.
partitionEithers :: [Either a b] -> ([a], [b])
-- | Extracts from a list of Either all the Left elements All
-- the Left elements are extracted in order.
lefts :: [Either a b] -> [a]
-- | Extracts from a list of Either all the Right elements
-- All the Right elements are extracted in order.
rights :: [Either a b] -> [b]
-- | (*) `on` f = \x y -> f x * f y.
--
-- Typical usage: sortBy (compare `on`
-- fst).
--
-- Algebraic properties:
--
--
on :: (b -> b -> c) -> (a -> b) -> a -> a -> c
-- |
-- 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) ...
--
comparing :: Ord a => (b -> a) -> b -> b -> Ordering
equating :: Eq a => (b -> a) -> b -> b -> Bool
-- | A functor with application, providing operations to
--
--
-- - embed pure expressions (pure), and
-- - sequence computations and combine their results
-- (<*>).
--
--
-- A minimal complete definition must include implementations of these
-- functions satisfying the following laws:
--
--
--
-- The other methods have the following default definitions, which may be
-- overridden with equivalent specialized implementations:
--
--
-- u *> v = pure (const id) <*> u <*> v
-- u <* v = pure const <*> u <*> v
--
--
-- As a consequence of these laws, the Functor instance for
-- f will satisfy
--
--
-- fmap f x = pure f <*> x
--
--
-- If f is also a Monad, it should satisfy
-- pure = return and (<*>) =
-- ap (which implies that pure and <*>
-- satisfy the applicative functor laws).
class Functor f => Applicative (f :: * -> *)
pure :: Applicative f => a -> f a
(<*>) :: Applicative f => f (a -> b) -> f a -> f b
(*>) :: Applicative f => f a -> f b -> f b
(<*) :: Applicative f => f a -> f b -> f a
-- | An infix synonym for fmap.
(<$>) :: Functor f => (a -> b) -> f a -> f b
-- | An associative binary operation
(<|>) :: Alternative f => forall a. f a -> f a -> f a
-- | Left-to-right Kleisli composition of monads.
(>=>) :: Monad m => (a -> m b) -> (b -> m c) -> a -> m c
-- | Lift a computation from the argument monad to the constructed monad.
lift :: MonadTrans t => forall (m :: * -> *) a. Monad m => m a -> t m a
-- | 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:
--
--
class Monad m => MonadIO (m :: * -> *)
liftIO :: MonadIO m => IO a -> m a
-- | Lift a computation from the IO monad.
liftIO :: MonadIO m => forall a. IO a -> m a
-- | 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, Typeable)
--
-- instance Exception MyException
--
--
-- The 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
-- deriving Typeable
--
-- 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
-- deriving Typeable
--
-- 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 (Typeable, Show)
--
-- instance Exception MismatchedParentheses where
-- toException = frontendExceptionToException
-- fromException = frontendExceptionFromException
--
--
-- We 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
--
class (Typeable e, Show e) => Exception e
toException :: Exception e => e -> SomeException
fromException :: Exception e => SomeException -> Maybe e
-- | The class Typeable allows a concrete representation of a type
-- to be calculated.
class Typeable a
typeOf :: Typeable a => a -> TypeRep
-- | 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.
data SomeException :: *
-- | 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.
data IOException :: *
-- | Generalized version of throwIO.
throwIO :: (MonadBase IO m, Exception e) => e -> m a
-- | Generalized version of try.
--
-- Note, when the given computation throws an exception any monadic side
-- effects in m will be discarded.
try :: (MonadBaseControl IO m, Exception e) => m a -> m (Either e a)
-- | Generalized version of catch.
--
-- Note, when the given computation throws an exception any monadic side
-- effects in m will be discarded.
catch :: (MonadBaseControl IO m, Exception e) => m a -> (e -> m a) -> m a
-- | Generalized version of handle.
--
-- Note, when the given computation throws an exception any monadic side
-- effects in m will be discarded.
handle :: (MonadBaseControl IO m, Exception e) => (e -> m a) -> m a -> m a
-- | Generalized version of bracket.
--
-- Note:
--
--
-- - When the "acquire" or "release" computations throw exceptions any
-- monadic side effects in m will be discarded.
-- - When the "in-between" computation throws an exception any monadic
-- side effects in m produced by that computation will be
-- discarded but the side effects of the "acquire" or "release"
-- computations will be retained.
-- - Also, any monadic side effects in m of the "release"
-- computation will be discarded; it is run only for its side effects in
-- IO.
--
--
-- Note that when your acquire and release computations
-- are of type IO it will be more efficient to write:
--
--
-- liftBaseOp (bracket acquire release)
--
bracket :: MonadBaseControl IO m => m a -> (a -> m b) -> (a -> m c) -> m c
-- | Generalized version of onException.
--
-- Note, any monadic side effects in m of the "afterward"
-- computation will be discarded.
onException :: MonadBaseControl IO m => m a -> m b -> m a
-- | Generalized version of finally.
--
-- Note, any monadic side effects in m of the "afterward"
-- computation will be discarded.
finally :: MonadBaseControl IO m => m a -> m b -> m a
data FilePath :: *
-- | An alias for append.
() :: FilePath -> FilePath -> FilePath
-- | An alias for addExtension.
(<.>) :: FilePath -> Text -> FilePath
-- | Get whether a FilePath’s last extension is the predicate.
hasExtension :: FilePath -> Text -> Bool
-- | Retrieve a FilePath’s basename component.
--
--
-- basename "foo/bar.txt" == "bar"
--
basename :: FilePath -> FilePath
-- | Retrieve a FilePath’s filename component.
--
--
-- filename "foo/bar.txt" == "bar.txt"
--
filename :: FilePath -> FilePath
-- | Retrieves the FilePath’s directory. If the path is already a
-- directory, it is returned unchanged.
directory :: FilePath -> FilePath
-- | Return a hash value for the argument. Defined in terms of
-- hashWithSalt and a default salt.
--
-- (See the "Hashing and security" section of the
-- Data.Hashable#security documentation for an important note on
-- working safely with untrusted user input.)
hash :: Hashable a => a -> Int
-- | Return a hash value for the argument, using the given salt.
--
-- The general contract of hashWithSalt is:
--
--
-- - If a value is hashed using the same salt during distinct runs of
-- an application, the result must remain the same. (This is necessary to
-- make it possible to store hashes on persistent media.)
-- - If two values are equal according to the == method, then
-- applying the hashWithSalt method 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 the hashWithSalt method
-- on each of the two values must produce distinct integer results.
-- (Every programmer will be aware that producing distinct integer
-- results for unequal values will 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 hashWithSalt
-- must make use of the salt in its implementation.
hashWithSalt :: Hashable a => Int -> a -> Int
-- | The print function outputs a value of any printable type to the
-- standard output device. Printable types are those that are instances
-- of class Show; print converts values to strings for
-- output using the show operation and adds a newline.
--
-- For example, a program to print the first 20 integers and their powers
-- of 2 could be written as:
--
--
-- main = print ([(n, 2^n) | n <- [0..19]])
--
print :: Show a => a -> IO ()
readArgs :: (MonadIO m, ArgumentTuple a) => m a
-- | BasicPrelude mostly re-exports several key libraries in their
-- entirety. The exception is Data.List, where various functions are
-- replaced by similar versions that are either generalized, operate on
-- Text, or are implemented strictly.
module BasicPrelude
-- |
-- map = fmap
--
map :: Functor f => (a -> b) -> f a -> f b
-- |
-- empty = mempty
--
empty :: Monoid w => w
-- |
-- (++) = mappend
--
(++) :: Monoid w => w -> w -> w
-- |
-- concat = mconcat
--
concat :: Monoid w => [w] -> w
-- |
-- intercalate = mconcat .: intersperse
--
intercalate :: Monoid w => w -> [w] -> w
-- | Compute the sum of a finite list of numbers.
sum :: Num a => [a] -> a
-- | Compute the product of a finite list of numbers.
product :: Num a => [a] -> a
-- | Convert a value to readable Text
show :: Show a => a -> Text
-- | Parse Text to a value
read :: Read a => Text -> a
-- | The readIO function is similar to read except that it signals parse
-- failure to the IO monad instead of terminating the program.
readIO :: Read a => Text -> IO a
-- | Read a file and return the contents of the file as Text. The entire
-- file is read strictly.
readFile :: FilePath -> IO Text
-- | Write Text to a file. The file is truncated to zero length before
-- writing begins.
writeFile :: FilePath -> Text -> IO ()
-- | Write Text to the end of a file.
appendFile :: FilePath -> Text -> IO ()
-- | O(n) Breaks a Text up into a list of Texts at
-- newline Chars. The resulting strings do not contain newlines.
lines :: Text -> [Text]
-- | O(n) Breaks a Text up into a list of words, delimited by
-- Chars representing white space.
words :: Text -> [Text]
-- | O(n) Joins lines, after appending a terminating newline to
-- each.
unlines :: [Text] -> Text
-- | O(n) Joins words using single space characters.
unwords :: [Text] -> Text
textToString :: Text -> String
ltextToString :: LText -> String
-- | Write a string to stdout.
putStr :: Text -> IO ()
-- | Read a single line of user input from stdin.
getLine :: IO Text
-- | Lazily read all user input on stdin as a single string.
getContents :: IO Text
-- | The interact function takes a function of type Text ->
-- Text as its argument. The entire input from the standard input
-- device is passed (lazily) to this function as its argument, and the
-- resulting string is output on the standard output device.
interact :: (Text -> Text) -> IO ()
-- | gcd x y is the non-negative factor of both x
-- and y of which every common factor of x and
-- y is also a factor; for example gcd 4 2 = 2,
-- gcd (-4) 6 = 2, gcd 0 4 = 4.
-- gcd 0 0 = 0. (That is, the common divisor
-- that is "greatest" in the divisibility preordering.)
--
-- Note: Since for signed fixed-width integer types, abs
-- minBound < 0, the result may be negative if one of the
-- arguments is minBound (and necessarily is if the other
-- is 0 or minBound) for such types.
gcd :: Integral a => a -> a -> a
-- | lcm x y is the smallest positive integer that both
-- x and y divide.
lcm :: Integral a => a -> a -> a
-- | A String is a list of characters. String constants in Haskell
-- are values of type String.
type String = [Char]
-- | The shows functions return a function that prepends the
-- output String to an existing String. This allows
-- constant-time concatenation of results using function composition.
type ShowS = String -> String
-- | 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.
showsPrec :: Show a => Int -> a -> ShowS
-- | The method showList is provided to allow the programmer to give
-- a specialised way of showing lists of values. For example, this is
-- used by the predefined Show instance of the Char type,
-- where values of type String should be shown in double quotes,
-- rather than between square brackets.
showList :: Show a => [a] -> ShowS
-- | equivalent to showsPrec with a precedence of 0.
shows :: Show a => a -> ShowS
-- | utility function converting a Char to a show function that
-- simply prepends the character unchanged.
showChar :: Char -> ShowS
-- | utility function converting a String to a show function that
-- simply prepends the string unchanged.
showString :: String -> ShowS
-- | utility function that surrounds the inner show function with
-- parentheses when the Bool parameter is True.
showParen :: Bool -> ShowS -> ShowS
-- | 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)]
-- | 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.
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]
-- | equivalent to readsPrec with a precedence of 0.
reads :: Read a => ReadS 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
-- | Write a character to the standard output device (same as
-- hPutChar stdout).
putChar :: Char -> IO ()
-- | Read a character from the standard input device (same as
-- hGetChar stdin).
getChar :: IO Char
-- | The readLn function combines getLine and readIO.
readLn :: Read a => IO a
-- | The Haskell 98 type for exceptions in the IO monad. Any I/O
-- operation may raise an IOError instead of returning a result.
-- For a more general type of exception, including also those that arise
-- in pure code, see Control.Exception.Exception.
--
-- In Haskell 98, this is an opaque type.
type IOError = IOException
-- | Raise an IOError in the IO monad.
ioError :: IOError -> IO a
-- | Construct an IOError value with a string describing the error.
-- The fail method of the IO instance of the Monad
-- class raises a userError, thus:
--
--
-- instance Monad IO where
-- ...
-- fail s = ioError (userError s)
--
userError :: String -> IOError