Safe Haskell	Safe-Infered

ClassyPrelude

Contents

Standard
Re-exports
Non-standard

Synopsis

Standard

Operators

($) :: (a -> b) -> a -> b

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.

(+) :: Num a => a -> a -> a

(-) :: Num a => a -> a -> a

(*) :: Num a => a -> a -> a

(/) :: Fractional a => a -> a -> a

fractional division

(&&) :: Bool -> Bool -> Bool

Boolean "and"

(||) :: Bool -> Bool -> Bool

Boolean "or"

(.) :: (b -> c) -> (a -> b) -> a -> c

Function composition.

Functions

not :: Bool -> Bool

Boolean "not"

otherwise :: Bool

otherwise is defined as the value True. It helps to make guards more readable. eg.

  f x | x < 0     = ...
      | otherwise = ...

fst :: (a, b) -> a

Extract the first component of a pair.

snd :: (a, b) -> b

Extract the second component of a pair.

id :: a -> a

Identity function.

maybe :: b -> (a -> b) -> Maybe a -> b

The maybe function takes a default value, a function, and a Maybe value. If the Maybe value is Nothing, the function returns the default value. Otherwise, it applies the function to the value inside the Just and returns the result.

either :: (a -> c) -> (b -> c) -> Either a b -> c

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.

flip :: (a -> b -> c) -> b -> a -> c

flip f takes its (first) two arguments in the reverse order of f.

const :: a -> b -> a

Constant function.

error :: [Char] -> a

error stops execution and displays an error message.

zip :: [a] -> [b] -> [(a, b)]

zip takes two lists and returns a list of corresponding pairs. If one input list is short, excess elements of the longer list are discarded.

unzip :: [(a, b)] -> ([a], [b])

unzip transforms a list of pairs into a list of first components and a list of second components.

zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]

zipWith generalises zip by zipping with the function given as the first argument, instead of a tupling function. For example, zipWith (+) is applied to two lists to produce the list of corresponding sums.

or :: [Bool] -> Bool

or returns the disjunction of a Boolean list. For the result to be False, the list must be finite; True, however, results from a True value at a finite index of a finite or infinite list.

putStrLn :: Text -> IO ()

Write a string to stdout, followed by a newline.

elem :: Eq a => a -> [a] -> Bool

elem is the list membership predicate, usually written in infix form, e.g., x `elem` xs. For the result to be False, the list must be finite; True, however, results from an element equal to x found at a finite index of a finite or infinite list.

odd :: Integral a => a -> Bool

even :: Integral a => a -> Bool

uncurry :: (a -> b -> c) -> (a, b) -> c

uncurry converts a curried function to a function on pairs.

Type classes

class Eq a => Ord a where

The Ord class is used for totally ordered datatypes.

Instances of Ord can be derived for any user-defined datatype whose constituent types are in Ord. The declared order of the constructors in the data declaration determines the ordering in derived Ord instances. The Ordering datatype allows a single comparison to determine the precise ordering of two objects.

Minimal complete definition: either compare or <=. Using compare can be more efficient for complex types.

Methods

compare :: a -> a -> Ordering

(<) :: a -> a -> Bool

(>=) :: a -> a -> Bool

(>) :: a -> a -> Bool

(<=) :: a -> a -> Bool

max :: a -> a -> a

min :: a -> a -> a

Instances

Ord Bool
Ord Char
Ord Double
Ord Float
Ord Int
Ord Int8
Ord Int16
Ord Int32
Ord Int64
Ord Ordering
Ord Word
Ord Word8
Ord Word16
Ord Word32
Ord Word64
Ord ()
Ord All
Ord Any
Ord ArithException
Ord TypeRep
Ord TyCon
Ord ByteString
Ord ByteString
Ord Arity
Ord Fixity
Ord Associativity
Ord Text
Ord Root
Ord FilePath
Ord Text
Ord a => Ord [a]
Integral a => Ord (Ratio a)
Ord a => Ord (Dual a)
Ord a => Ord (Sum a)
Ord a => Ord (Product a)
Ord a => Ord (First a)
Ord a => Ord (Last a)
Ord a => Ord (Maybe a)
Ord a => Ord (Set a)
Ord a => Ord (Vector a)
(Ord a, Ord b) => Ord (Either a b)
(Ord a, Ord b) => Ord (a, b)
(Ord k, Ord v) => Ord (Map k v)
Ord a => Ord (Stream Id a)
(Ord a, Ord b, Ord c) => Ord (a, b, c)
(Ord a, Ord b, Ord c, Ord d) => Ord (a, b, c, d)
(Ord a, Ord b, Ord c, Ord d, Ord e) => Ord (a, b, c, d, e)
(Ord a, Ord b, Ord c, Ord d, Ord e, Ord f) => Ord (a, b, c, d, e, f)
(Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g) => Ord (a, b, c, d, e, f, g)
(Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h) => Ord (a, b, c, d, e, f, g, h)
(Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h, Ord i) => Ord (a, b, c, d, e, f, g, h, i)
(Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h, Ord i, Ord j) => Ord (a, b, c, d, e, f, g, h, i, j)
(Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h, Ord i, Ord j, Ord k) => Ord (a, b, c, d, e, f, g, h, i, j, k)
(Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h, Ord i, Ord j, Ord k, Ord l) => Ord (a, b, c, d, e, f, g, h, i, j, k, l)
(Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h, Ord i, Ord j, Ord k, Ord l, Ord m) => Ord (a, b, c, d, e, f, g, h, i, j, k, l, m)
(Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h, Ord i, Ord j, Ord k, Ord l, Ord m, Ord n) => Ord (a, b, c, d, e, f, g, h, i, j, k, l, m, n)
(Ord a, Ord b, Ord c, Ord d, Ord e, Ord f, Ord g, Ord h, Ord i, Ord j, Ord k, Ord l, Ord m, Ord n, Ord o) => Ord (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o)

class Eq a where

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 /=.

Methods

(==) :: a -> a -> Bool

(/=) :: a -> a -> Bool

Instances

Eq Bool
Eq Char
Eq Double
Eq Float
Eq Int
Eq Int8
Eq Int16
Eq Int32
Eq Int64
Eq Ordering
Eq Word
Eq Word8
Eq Word16
Eq Word32
Eq Word64
Eq ()
Eq All
Eq Any
Eq MaskingState
Eq ArithException
Eq TypeRep
Eq TyCon
Eq ByteString
Eq ByteString
Eq Arity
Eq Fixity
Eq Associativity
Eq Text
Eq Root
Eq FilePath
Eq Text
Eq a => Eq [a]
Eq a => Eq (Ratio a)
Eq a => Eq (Dual a)
Eq a => Eq (Sum a)
Eq a => Eq (Product a)
Eq a => Eq (First a)
Eq a => Eq (Last a)
Eq a => Eq (Maybe a)
Eq a => Eq (Set a)
(Hashable a, Eq a) => Eq (HashSet a)
Eq a => Eq (Vector a)
(Eq a, Eq b) => Eq (Either a b)
(Eq a, Eq b) => Eq (a, b)
(Eq k, Eq a) => Eq (Map k a)
(Eq k, Eq v) => Eq (HashMap k v)
Eq a => Eq (Stream Id a)
(Eq a, Eq b, Eq c) => Eq (a, b, c)
(Eq a, Eq b, Eq c, Eq d) => Eq (a, b, c, d)
(Eq a, Eq b, Eq c, Eq d, Eq e) => Eq (a, b, c, d, e)
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f) => Eq (a, b, c, d, e, f)
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g) => Eq (a, b, c, d, e, f, g)
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h) => Eq (a, b, c, d, e, f, g, h)
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i) => Eq (a, b, c, d, e, f, g, h, i)
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j) => Eq (a, b, c, d, e, f, g, h, i, j)
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k) => Eq (a, b, c, d, e, f, g, h, i, j, k)
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k, Eq l) => Eq (a, b, c, d, e, f, g, h, i, j, k, l)
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k, Eq l, Eq m) => Eq (a, b, c, d, e, f, g, h, i, j, k, l, m)
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k, Eq l, Eq m, Eq n) => Eq (a, b, c, d, e, f, g, h, i, j, k, l, m, n)
(Eq a, Eq b, Eq c, Eq d, Eq e, Eq f, Eq g, Eq h, Eq i, Eq j, Eq k, Eq l, Eq m, Eq n, Eq o) => Eq (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o)

class Enum a where

Class Enum defines operations on sequentially ordered types.

The enumFrom... methods are used in Haskell's translation of arithmetic sequences.

Instances of Enum may be derived for any enumeration type (types whose constructors have no fields). The nullary constructors are assumed to be numbered left-to-right by fromEnum from 0 through n-1. See Chapter 10 of the Haskell Report for more details.

For any type that is an instance of class Bounded as well as Enum, the following should hold:

The calls succ maxBound and pred minBound should result in a runtime error.
fromEnum and toEnum should give a runtime error if the result value is not representable in the result type. For example, toEnum 7 :: Bool is an error.
enumFrom and enumFromThen should be defined with an implicit bound, thus:

    enumFrom     x   = enumFromTo     x maxBound
    enumFromThen x y = enumFromThenTo x y bound
      where
        bound | fromEnum y >= fromEnum x = maxBound
              | otherwise                = minBound

Methods

succ :: a -> a

the successor of a value. For numeric types, succ adds 1.

pred :: a -> a

the predecessor of a value. For numeric types, pred subtracts 1.

toEnum :: Int -> a

Convert from an Int.

fromEnum :: a -> Int

Convert to an Int. It is implementation-dependent what fromEnum returns when applied to a value that is too large to fit in an Int.

enumFrom :: a -> [a]

Used in Haskell's translation of [n..].

enumFromThen :: a -> a -> [a]

Used in Haskell's translation of [n,n'..].

enumFromTo :: a -> a -> [a]

Used in Haskell's translation of [n..m].

enumFromThenTo :: a -> a -> a -> [a]

Used in Haskell's translation of [n,n'..m].

Instances

Enum Bool
Enum Char
Enum Double
Enum Float
Enum Int
Enum Int8
Enum Int16
Enum Int32
Enum Int64
Enum Integer
Enum Ordering
Enum Word
Enum Word8
Enum Word16
Enum Word32
Enum Word64
Enum ()
Integral a => Enum (Ratio a)

class Show 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)".

Instances

Show Bool
Show Char
Show Double
Show Float
Show Int
Show Int8
Show Int16
Show Int32
Show Int64
Show Integer
Show Ordering
Show Word
Show Word8
Show Word16
Show Word32
Show Word64
Show ()
Show All
Show Any
Show MaskingState
Show SomeException
Show ErrorCall
Show ArithException
Show TypeRep
Show TyCon
Show ByteString
Show ByteString
Show Arity
Show Fixity
Show Associativity
Show Text
Show FilePath
Show Text
Show a => Show [a]
(Integral a, Show a) => Show (Ratio a)
Show a => Show (Dual a)
Show a => Show (Sum a)
Show a => Show (Product a)
Show a => Show (First a)
Show a => Show (Last a)
Show a => Show (Maybe a)
Show a => Show (Set a)
Show (Rules a)
Show a => Show (HashSet a)
Show a => Show (Vector a)
(Show a, Show b) => Show (Either a b)
(Show a, Show b) => Show (a, b)
(Show k, Show a) => Show (Map k a)
(Show k, Show v) => Show (HashMap k v)
(Show a, Show b, Show c) => Show (a, b, c)
(Show a, Show b, Show c, Show d) => Show (a, b, c, d)
(Show a, Show b, Show c, Show d, Show e) => Show (a, b, c, d, e)
(Show a, Show b, Show c, Show d, Show e, Show f) => Show (a, b, c, d, e, f)
(Show a, Show b, Show c, Show d, Show e, Show f, Show g) => Show (a, b, c, d, e, f, g)
(Show a, Show b, Show c, Show d, Show e, Show f, Show g, Show h) => Show (a, b, c, d, e, f, g, h)
(Show a, Show b, Show c, Show d, Show e, Show f, Show g, Show h, Show i) => Show (a, b, c, d, e, f, g, h, i)
(Show a, Show b, Show c, Show d, Show e, Show f, Show g, Show h, Show i, Show j) => Show (a, b, c, d, e, f, g, h, i, j)
(Show a, Show b, Show c, Show d, Show e, Show f, Show g, Show h, Show i, Show j, Show k) => Show (a, b, c, d, e, f, g, h, i, j, k)
(Show a, Show b, Show c, Show d, Show e, Show f, Show g, Show h, Show i, Show j, Show k, Show l) => Show (a, b, c, d, e, f, g, h, i, j, k, l)
(Show a, Show b, Show c, Show d, Show e, Show f, Show g, Show h, Show i, Show j, Show k, Show l, Show m) => Show (a, b, c, d, e, f, g, h, i, j, k, l, m)
(Show a, Show b, Show c, Show d, Show e, Show f, Show g, Show h, Show i, Show j, Show k, Show l, Show m, Show n) => Show (a, b, c, d, e, f, g, h, i, j, k, l, m, n)
(Show a, Show b, Show c, Show d, Show e, Show f, Show g, Show h, Show i, Show j, Show k, Show l, Show m, Show n, Show o) => Show (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o)

class Functor f where

The Functor class is used for types that can be mapped over. Instances of Functor should satisfy the following laws:

 fmap id  ==  id
 fmap (f . g)  ==  fmap f . fmap g

The instances of Functor for lists, Maybe and IO satisfy these laws.

Methods

fmap :: (a -> b) -> f a -> f b

(<$) :: a -> f b -> f a

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.

Instances

Functor []
Functor IO
Functor ZipList
Functor Maybe
Functor Vector
Functor ((->) r)
Functor (Either a)
Functor ((,) a)
Functor (Const m)
Monad m => Functor (WrappedMonad m)
Functor (Map k)
Functor (HashMap k)
Arrow a => Functor (WrappedArrow a b)

class Monad m where

The Monad class defines the basic operations over a monad, a concept from a branch of mathematics known as category theory. From the perspective of a Haskell programmer, however, it is best to think of a monad as an abstract datatype of actions. Haskell's do expressions provide a convenient syntax for writing monadic expressions.

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.

Methods

(>>=) :: m a -> (a -> m b) -> m b

Sequentially compose two actions, passing any value produced by the first as an argument to the second.

(>>) :: m 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.

return :: a -> m a

Inject a value into the monadic type.

fail :: String -> m a

Fail with a message. This operation is not part of the mathematical definition of a monad, but is invoked on pattern-match failure in a do expression.

Instances

Monad []
Monad IO
Monad Maybe
Monad Vector
Monad ((->) r)
Monad (Either e)
ArrowApply a => Monad (ArrowMonad a)

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

Same as >>=, but with the arguments interchanged.

Data types

data Maybe 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.

Constructors

Nothing
Just a

Instances

Monad Maybe
Functor Maybe
Typeable1 Maybe
MonadPlus Maybe
Applicative Maybe
Alternative Maybe
Eq a => Eq (Maybe a)
Ord a => Ord (Maybe a)
Show a => Show (Maybe a)
Generic (Maybe a)
Monoid a => Monoid (Maybe a)	Lift a semigroup into `Maybe` forming a `Monoid` according to http://en.wikipedia.org/wiki/Monoid: "Any semigroup `S` may be turned into a monoid simply by adjoining an element `e` not in `S` and defining `ee = e` and `es = s = s*e` for all `s ∈ S`." Since there is no "Semigroup" typeclass providing just `mappend`, we use `Monoid` instead.
Hashable a => Hashable (Maybe a)
CanPack (Maybe a) a

data Ordering

Constructors

LT
EQ
GT

Instances

Bounded Ordering
Enum Ordering
Eq Ordering
Ord Ordering
Show Ordering
Typeable Ordering
Generic Ordering
Monoid Ordering

data Bool

Constructors

False
True

Instances

Bounded Bool
Enum Bool
Eq Bool
Ord Bool
Show Bool
Typeable Bool
Generic Bool
Hashable Bool

data Char

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 IO a

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.

Instances

Monad IO
Functor IO
Typeable1 IO
Applicative IO
PrimMonad IO
MonadIO IO

data Either a b

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").

Constructors

Left a
Right b

Instances

Typeable2 Either
Monad (Either e)
Functor (Either a)
Applicative (Either e)
(Eq a, Eq b) => Eq (Either a b)
(Ord a, Ord b) => Ord (Either a b)
(Read a, Read b) => Read (Either a b)
(Show a, Show b) => Show (Either a b)
Generic (Either a b)
(Hashable a, Hashable b) => Hashable (Either a b)

class (Real a, Enum a) => Integral a where

Integral numbers, supporting integer division.

Minimal complete definition: quotRem and toInteger

Methods

quot :: a -> a -> a

integer division truncated toward zero

rem :: a -> a -> a

integer remainder, satisfying

 (x `quot` y)*y + (x `rem` y) == x

div :: a -> a -> a

integer division truncated toward negative infinity

mod :: a -> a -> a

integer modulus, satisfying

 (x `div` y)*y + (x `mod` y) == x

quotRem :: a -> a -> (a, a)

simultaneous quot and rem

divMod :: a -> a -> (a, a)

simultaneous div and mod

toInteger :: a -> Integer

conversion to Integer

Instances

Integral Int
Integral Int8
Integral Int16
Integral Int32
Integral Int64
Integral Integer
Integral Word
Integral Word8
Integral Word16
Integral Word32
Integral Word64

Re-exports

Packed reps

data ByteString

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

Instances

Eq ByteString
Data ByteString
Ord ByteString
Read ByteString
Show ByteString
Typeable ByteString
IsString ByteString
Monoid ByteString
Hashable ByteString
CanWriteFileFunc ByteString
CanEmpty ByteString
CanNull ByteString
CanSplitAt ByteString Int
CanAny ByteString Word8
CanBreak ByteString Word8
CanPack ByteString Word8
CanSingleton ByteString Word8
CanLength ByteString Int
CanFilterFunc ByteString Word8
(~ * co ByteString, ~ * i Word8, ~ * o ByteString) => CanConcatMapFunc ByteString co i o
(~ * co ByteString, ~ * i Word8, ~ * o Word8) => CanMapFunc ByteString co i o
MonadIO m => CanReadFile (m ByteString)

type LByteString = ByteString Source

data Text

A space efficient, packed, unboxed Unicode text type.

Instances

Eq Text
Data Text
Ord Text
Read Text
Show Text
Typeable Text
IsString Text
Monoid Text
NFData Text
Hashable Text
CanStripPrefix Text
CanEmpty Text
CanNull Text
CanSplitAt Text Int
CanAny Text Char
CanBreak Text Char
CanPack Text Char
CanSingleton Text Char
CanLength Text Int
CanFilterFunc Text Char
(~ * co Text, ~ * i Char, ~ * o Text) => CanConcatMapFunc Text co i o
(~ * co Text, ~ * i Char, ~ * o Char) => CanMapFunc Text co i o

type LText = Text Source

Containers

data Map k a

A Map from keys k to values a.

Instances

Typeable2 Map
Functor (Map k)
Foldable (Map k)
Traversable (Map k)
(Eq k, Eq a) => Eq (Map k a)
(Data k, Data a, Ord k) => Data (Map k a)
(Ord k, Ord v) => Ord (Map k v)
(Ord k, Read k, Read e) => Read (Map k e)
(Show k, Show a) => Show (Map k a)
Ord k => Monoid (Map k v)
(NFData k, NFData a) => NFData (Map k a)
CanEmpty (Map k v)
CanNull (Map k v)
Ord k => CanDelete (Map k v) k
~ * v' v => CanSingleton (v' -> Map k v) k
CanLength (Map k v) Int
Ord k => CanInsertVal (Map k v) k v
Ord k => CanLookup (Map k v) k v
Ord k => CanPack (Map k v) (k, v)
Ord k => CanFilterFunc (Map k v) (k, v)
CanMapFunc (Map k v1) (Map k v2) v1 v2

data HashMap k v

A map from keys to values. A map cannot contain duplicate keys; each key can map to at most one value.

Instances

Typeable2 HashMap
Functor (HashMap k)
Foldable (HashMap k)
Traversable (HashMap k)
(Eq k, Eq v) => Eq (HashMap k v)
(Show k, Show v) => Show (HashMap k v)
(Eq k, Hashable k) => Monoid (HashMap k v)
(NFData k, NFData v) => NFData (HashMap k v)
CanEmpty (Map k v)
CanEmpty (Map k v)
CanNull (Map k v)
CanNull (Map k v)
(Eq k, Hashable k) => CanDelete (Map k v) k
(Eq k, Hashable k) => CanDelete (Map k v) k
(Eq k, Hashable k, ~ * v' v) => CanSingleton (v' -> Map k v) k
(Eq k, Hashable k, ~ * v' v) => CanSingleton (v' -> Map k v) k
CanLength (Map k v) Int
CanLength (Map k v) Int
(Eq k, Hashable k) => CanInsertVal (Map k v) k v
(Eq k, Hashable k) => CanInsertVal (Map k v) k v
(Eq k, Hashable k) => CanLookup (Map k v) k v
(Eq k, Hashable k) => CanLookup (Map k v) k v
(Eq k, Hashable k) => CanPack (Map k v) (k, v)
(Eq k, Hashable k) => CanPack (Map k v) (k, v)
Hashable k => CanFilterFunc (Map k v) (k, v)
Hashable k => CanFilterFunc (Map k v) (k, v)
CanMapFunc (Map k v1) (Map k v2) v1 v2
CanMapFunc (Map k v1) (Map k v2) v1 v2

type LHashMap = HashMap Source

data Set a

A set of values a.

Instances

Typeable1 Set
Foldable Set
Eq a => Eq (Set a)
(Data a, Ord a) => Data (Set a)
Ord a => Ord (Set a)
(Read a, Ord a) => Read (Set a)
Show a => Show (Set a)
Ord a => Monoid (Set a)
NFData a => NFData (Set a)
CanEmpty (Set x)
CanNull (Set x)
Ord x => CanMember (Set x) x
Ord x => CanPack (Set x) x
CanSingleton (Set x) x
CanLength (Set x) Int
(Ord a, Ord b) => CanMapFunc (Set a) (Set b) a b
(Ord x, ~ * (Set x) s, ~ * x x') => CanInsert (x' -> s -> Set x)

data HashSet a

A set of values. A set cannot contain duplicate values.

Instances

Foldable HashSet
(Hashable a, Eq a) => Eq (HashSet a)
Show a => Show (HashSet a)
(Hashable a, Eq a) => Monoid (HashSet a)
NFData a => NFData (HashSet a)
CanEmpty (Set x)
CanNull (Set x)
(Eq x, Hashable x) => CanMember (Set x) x
(Hashable x, Eq x) => CanPack (Set x) x
Hashable x => CanSingleton (Set x) x
CanLength (Set x) Int
(Eq b, Hashable b) => CanMapFunc (Set a) (Set b) a b
(Eq x, Hashable x, ~ * (Set x) s, ~ * x x') => CanInsert (x' -> s -> Set x)

data Vector a

Boxed vectors, supporting efficient slicing.

Instances

Monad Vector
Functor Vector
Typeable1 Vector
MonadPlus Vector
Applicative Vector
Foldable Vector
Traversable Vector
Alternative Vector
Vector Vector a
Eq a => Eq (Vector a)
Data a => Data (Vector a)
Ord a => Ord (Vector a)
Read a => Read (Vector a)
Show a => Show (Vector a)
Monoid (Vector a)
CanEmpty (Vector a)
CanNull (Vector a)
CanSplitAt (Vector a) Int
CanAny (Vector a) a
CanBreak (Vector a) a
Eq x => CanMember (Vector x) x
CanPack (Vector a) a
CanSingleton (Vector a) a
CanLength (Vector a) Int
CanFilterFunc (Vector a) a
CanFoldFunc (Vector a) accum a
Monad m => CanMapM_Func (Vector a) a b m
(~ * i a, ~ * co (Vector b)) => CanMapFunc (Vector a) co i b
(~ * i a, ~ * co (Vector b)) => CanConcatMapFunc (Vector a) co i (Vector b)
Monad m => CanMapMFunc (Vector a) (Vector b) a b m

Numbers

data Word8

8-bit unsigned integer type

data Word64

64-bit unsigned integer type

Instances

Bounded Word64
Enum Word64
Eq Word64
Integral Word64
Num Word64
Ord Word64
Read Word64
Real Word64
Show Word64
Ix Word64
Typeable Word64
Bits Word64
Hashable Word64

data Int64

64-bit signed integer type

data Int

A fixed-precision integer type with at least the range [-2^29 .. 2^29-1]. The exact range for a given implementation can be determined by using minBound and maxBound from the Bounded class.

Instances

Bounded Int
Enum Int
Eq Int
Integral Int
Num Int
Ord Int
Real Int
Show Int
Typeable Int
Generic Int
Hashable Int
CanSplitAt ByteString Int
CanSplitAt Text Int
CanLength ByteString Int
CanLength Text Int
CanSplitAt [c] Int
CanSplitAt (Vector a) Int
CanLength [a] Int
CanLength (Set x) Int
CanLength (Vector a) Int
CanLength (Set x) Int
CanLength (Map k v) Int
CanLength (Map k v) Int
CanLength (Map k v) Int

data Word

A Word is an unsigned integral type, with the same size as Int.

Instances

Bounded Word
Enum Word
Eq Word
Integral Word
Num Word
Ord Word
Read Word
Real Word
Show Word
Ix Word
Typeable Word
Bits Word
Hashable Word

Monoids

class Monoid a where

The class of monoids (types with an associative binary operation that has an identity). Instances should satisfy the following laws:

```
mappend mempty x = x
```
```
mappend x mempty = x
```

mappend x (mappend y z) = mappend (mappend x y) z

```
mconcat = foldr mappend mempty
```

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.

Methods

mempty :: a

Identity of mappend

mappend :: a -> a -> a

An associative operation

mconcat :: [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.

Instances

Monoid Ordering
Monoid ()
Monoid All
Monoid Any
Monoid ByteString
Monoid ByteString
Monoid Text
Monoid FilePath
Monoid Text
Monoid [a]
Monoid a => Monoid (Dual a)
Monoid (Endo a)
Num a => Monoid (Sum a)
Num a => Monoid (Product a)
Monoid (First a)
Monoid (Last a)
Monoid a => Monoid (Maybe a)	Lift a semigroup into `Maybe` forming a `Monoid` according to http://en.wikipedia.org/wiki/Monoid: "Any semigroup `S` may be turned into a monoid simply by adjoining an element `e` not in `S` and defining `ee = e` and `es = s = s*e` for all `s ∈ S`." Since there is no "Semigroup" typeclass providing just `mappend`, we use `Monoid` instead.
Ord a => Monoid (Set a)
(Hashable a, Eq a) => Monoid (HashSet a)
Monoid (Vector a)
Monoid b => Monoid (a -> b)
(Monoid a, Monoid b) => Monoid (a, b)
Ord k => Monoid (Map k v)
(Eq k, Hashable k) => Monoid (HashMap k v)
(Monoid a, Monoid b, Monoid c) => Monoid (a, b, c)
(Monoid a, Monoid b, Monoid c, Monoid d) => Monoid (a, b, c, d)
(Monoid a, Monoid b, Monoid c, Monoid d, Monoid e) => Monoid (a, b, c, d, e)

concat :: Monoid w => [w] -> wSource

(++) :: Monoid w => w -> w -> wSource

Arrow

first :: Arrow a => forall b c d. a b c -> a (b, d) (c, d)

Send the first component of the input through the argument arrow, and copy the rest unchanged to the output.

second :: Arrow a => forall b c d. a b c -> a (d, b) (d, c)

A mirror image of first.

The default definition may be overridden with a more efficient version if desired.

(***) :: Arrow a => forall b c b' c'. a b c -> a b' c' -> a (b, b') (c, 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 c'. a b c -> a b c' -> a 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.

Maybe

mapMaybe :: (a -> Maybe b) -> [a] -> [b]

The mapMaybe function is a version of map which can throw out elements. In particular, the functional argument returns something of type Maybe 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.

catMaybes :: [Maybe a] -> [a]

The catMaybes function takes a list of Maybes and returns a list of all the Just values.

fromMaybe :: a -> Maybe a -> a

The fromMaybe function takes a default value and and Maybe value. If the Maybe is Nothing, it returns the default values; otherwise, it returns the value contained in the Maybe.

Either

partitionEithers :: [Either a b] -> ([a], [b])

Partitions a list of Either into two lists All the Left elements are extracted, in order, to the first component of the output. Similarly the Right elements are extracted to the second component of the output.

Applicative

class Functor f => Applicative f where

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:

identity: pure id <*> v = v
composition: pure (.) <*> u <*> v <*> w = u <*> (v <*> w)
homomorphism: pure f <*> pure x = pure (f x)
interchange: u <*> pure y = pure ($ y) <*> u

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).

Methods

pure :: a -> f a

Lift a value.

(<*>) :: f (a -> b) -> f a -> f b

Sequential application.

(*>) :: f a -> f b -> f b

Sequence actions, discarding the value of the first argument.

(<*) :: f a -> f b -> f a

Sequence actions, discarding the value of the second argument.

Instances

Applicative []
Applicative IO
Applicative ZipList
Applicative STM
Applicative Maybe
Applicative Vector
Applicative ((->) a)
Applicative (Either e)
Monoid a => Applicative ((,) a)
Applicative (ST s)
Monoid m => Applicative (Const m)
Monad m => Applicative (WrappedMonad m)
Applicative (ST s)
Arrow a => Applicative (WrappedArrow a b)

(<$>) :: Functor f => (a -> b) -> f a -> f b

An infix synonym for fmap.

Monad

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

Left-to-right Kleisli composition of monads.

Transformers

lift :: MonadTrans t => forall m a. Monad m => m a -> t m a

Lift a computation from the argument monad to the constructed monad.

class Monad m => MonadIO m where

Monads in which IO computations may be embedded. Any monad built by applying a sequence of monad transformers to the IO monad will be an instance of this class.

Instances should satisfy the following laws, which state that liftIO is a transformer of monads:

```
liftIO . return = return
```

liftIO (m >>= f) = liftIO m >>= (liftIO . f)

Methods

liftIO :: IO a -> m a

Lift a computation from the IO monad.

Instances

MonadIO IO

liftIO :: MonadIO m => forall a. IO a -> m a

Lift a computation from the IO monad.

Exceptions

class (Typeable e, Show e) => Exception e where

Any type that you wish to throw or catch as an exception must be an instance of the Exception class. The simplest case is a new exception type directly below the root:

 data MyException = ThisException | ThatException
     deriving (Show, 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

Methods

toException :: e -> SomeException

fromException :: SomeException -> Maybe e

Instances

Exception SomeException
Exception ErrorCall
Exception ArithException

data SomeException

The SomeException type is the root of the exception type hierarchy. When an exception of type e is thrown, behind the scenes it is encapsulated in a SomeException.

Instances

Show SomeException
Typeable SomeException
Exception SomeException

throwIO :: Exception e => e -> IO a

A variant of throw that can only be used within the IO monad.

Although throwIO has a type that is an instance of the type of throw, the two functions are subtly different:

 throw e   `seq` x  ===> throw e
 throwIO e `seq` x  ===> x

The first example will cause the exception e to be raised, whereas the second one won't. In fact, throwIO will only cause an exception to be raised when it is used within the IO monad. The throwIO variant should be used in preference to throw to raise an exception within the IO monad because it guarantees ordering with respect to other IO operations, whereas throw does not.

Files

(</>) :: FilePath -> FilePath -> FilePath

An alias for append.

(<.>) :: FilePath -> Text -> FilePath

An alias for addExtension.

hasExtension :: FilePath -> Text -> Bool

Get whether a FilePath’s last extension is the predicate.

basename :: FilePath -> FilePath

Retrieve a FilePath’s basename component.

 basename "foo/bar.txt" == "bar"

filename :: FilePath -> FilePath

Retrieve a FilePath’s filename component.

 filename "foo/bar.txt" == "bar.txt"

Non-standard

List-like classes

map :: CanMap f i o => (i -> o) -> fSource

concatMap :: CanConcatMap f i o => (i -> o) -> fSource

filter :: CanFilter f a => (a -> Bool) -> fSource

length :: CanLength c i => c -> iSource

singleton :: CanSingleton c i => i -> cSource

null :: CanNull c => c -> Bool Source

pack :: CanPack c i => [i] -> cSource

unpack :: CanPack c i => c -> [i]Source

fromList :: CanPack c i => [i] -> cSource

toList :: CanPack c i => c -> [i]Source

mapM :: CanMapM f i o m => (i -> m o) -> fSource

mapM_ :: CanMapM_ f i o m => (i -> m o) -> fSource

empty :: CanEmpty c => cSource

stripPrefix :: CanStripPrefix a => a -> a -> Maybe aSource

break :: CanBreak c i => (i -> Bool) -> c -> (c, c)Source

span :: CanBreak c i => (i -> Bool) -> c -> (c, c)Source

dropWhile :: CanBreak c i => (i -> Bool) -> c -> cSource

takeWhile :: CanBreak c i => (i -> Bool) -> c -> cSource

any :: CanAny c i => (i -> Bool) -> c -> Bool Source

all :: CanAny c i => (i -> Bool) -> c -> Bool Source

splitAt :: CanSplitAt c i => i -> c -> (c, c)Source

fold :: CanFold accum a f => (accum -> a -> accum) -> accum -> fSource

Strict left fold.

Map-like

lookup :: CanLookup c k v => k -> c -> Maybe vSource

insert :: CanInsert f => fSource

delete :: CanDelete c k => k -> c -> cSource

Set-like

member :: CanMember c k => k -> c -> Bool Source

Text-like

show :: (Show a, CanPack c Char) => a -> cSource

Files

readFile :: CanReadFile a => FilePath -> aSource

writeFile :: CanWriteFile a => FilePath -> aSource

Print

print :: Show a => a -> IO ()

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]])

Bounded Char
Enum Char
Eq Char
Ord Char
Show Char
Typeable Char
Generic Char
Hashable Char
CanAny Text Char
CanAny LText Char
CanBreak Text Char
CanBreak LText Char
CanPack Text Char
CanPack FilePath Char
CanPack LText Char
CanSingleton Text Char
CanSingleton LText Char
CanFilterFunc Text Char
CanFilterFunc LText Char

Bounded Word8
Enum Word8
Eq Word8
Integral Word8
Num Word8
Ord Word8
Read Word8
Real Word8
Show Word8
Ix Word8
Typeable Word8
Bits Word8
Hashable Word8
CanAny ByteString Word8
CanAny LByteString Word8
CanBreak ByteString Word8
CanBreak LByteString Word8
CanPack ByteString Word8
CanPack LByteString Word8
CanSingleton ByteString Word8
CanSingleton LByteString Word8
CanFilterFunc ByteString Word8
CanFilterFunc LByteString Word8

Bounded Int64
Enum Int64
Eq Int64
Integral Int64
Num Int64
Ord Int64
Read Int64
Real Int64
Show Int64
Ix Int64
Typeable Int64
Bits Int64
Hashable Int64
CanSplitAt LByteString Int64
CanSplitAt LText Int64
CanLength LByteString Int64

Eq FilePath
Data FilePath
Ord FilePath
Show FilePath
Typeable FilePath
IsString FilePath
Monoid FilePath
NFData FilePath
CanStripPrefix FilePath
CanPack FilePath Char