base-4.8.1.0: Basic libraries

Copyright(c) The University of Glasgow 2001
LicenseBSD-style (see the file libraries/base/LICENSE)
Maintainerlibraries@haskell.org
Stabilityprovisional
Portabilityportable
Safe HaskellSafe
LanguageHaskell2010

Text.Show

Description

Converting values to readable strings: the Show class and associated functions.

Synopsis

Documentation

type ShowS = String -> String Source

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.

class Show a where Source

Conversion of values to readable Strings.

Derived instances of Show have the following properties, which are compatible with derived instances of Read:

  • The result of 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)".

Minimal complete definition

showsPrec | show

Methods

showsPrec Source

Arguments

:: Int

the operator precedence of the enclosing context (a number from 0 to 11). Function application has precedence 10.

-> a

the value to be converted to a String

-> ShowS 

Convert a value to a readable String.

showsPrec should satisfy the law

showsPrec d x r ++ s  ==  showsPrec d x (r ++ s)

Derived instances of Read and Show satisfy the following:

That is, readsPrec parses the string produced by showsPrec, and delivers the value that showsPrec started with.

show :: a -> String Source

A specialised variant of showsPrec, using precedence context zero, and returning an ordinary String.

showList :: [a] -> ShowS Source

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.

Instances

Show Bool Source 
Show Char Source 
Show Int Source 
Show Int8 Source 
Show Int16 Source 
Show Int32 Source 
Show Int64 Source 
Show Integer Source 
Show Ordering Source 
Show Word Source 
Show Word8 Source 
Show Word16 Source 
Show Word32 Source 
Show Word64 Source 
Show CallStack Source 
Show TypeRep Source 
Show () Source 

Methods

showsPrec :: Int -> () -> ShowS Source

show :: () -> String Source

showList :: [()] -> ShowS Source

Show SomeException Source 
Show Number Source 
Show Lexeme Source 
Show GeneralCategory Source 
Show Fingerprint Source 
Show TyCon Source 
Show Associativity Source 
Show Fixity Source 
Show Arity Source 
Show Any Source 
Show All Source 
Show ArithException Source 
Show ErrorCall Source 
Show IOException Source 
Show MaskingState Source 
Show Dynamic Source 
Show CUIntMax Source 
Show CIntMax Source 
Show CUIntPtr Source 
Show CIntPtr Source 
Show CSUSeconds Source 
Show CUSeconds Source 
Show CTime Source 
Show CClock Source 
Show CSigAtomic Source 
Show CWchar Source 
Show CSize Source 
Show CPtrdiff Source 
Show CDouble Source 
Show CFloat Source 
Show CULLong Source 
Show CLLong Source 
Show CULong Source 
Show CLong Source 
Show CUInt Source 
Show CInt Source 
Show CUShort Source 
Show CShort Source 
Show CUChar Source 
Show CSChar Source 
Show CChar Source 
Show IntPtr Source 
Show WordPtr Source 
Show CodingProgress Source 
Show TextEncoding Source 
Show SeekMode Source 
Show NewlineMode Source 
Show Newline Source 
Show BufferMode Source 
Show Handle Source 
Show IOErrorType Source 
Show ExitCode Source 
Show ArrayException Source 
Show AsyncException Source 
Show SomeAsyncException Source 
Show AssertionFailed Source 
Show AllocationLimitExceeded Source 
Show Deadlock Source 
Show BlockedIndefinitelyOnSTM Source 
Show BlockedIndefinitelyOnMVar Source 
Show Fd Source 
Show CRLim Source 
Show CTcflag Source 
Show CSpeed Source 
Show CCc Source 
Show CUid Source 
Show CNlink Source 
Show CGid Source 
Show CSsize Source 
Show CPid Source 
Show COff Source 
Show CMode Source 
Show CIno Source 
Show CDev Source 
Show CodingFailureMode Source 
Show ThreadStatus Source 
Show BlockReason Source 
Show ThreadId Source 
Show NestedAtomically Source 
Show NonTermination Source 
Show NoMethodError Source 
Show RecUpdError Source 
Show RecConError Source 
Show RecSelError Source 
Show PatternMatchFail Source 
Show IOMode Source 
Show Lifetime Source 
Show Event Source 
Show FdKey Source 
Show HandlePosn Source 
Show GCStats Source 
Show Version Source 
Show Fixity Source 
Show ConstrRep Source 
Show DataRep Source 
Show Constr Source 
Show DataType Source 
Show Natural Source 
Show RTSFlags Source 
Show TickyFlags Source 
Show TraceFlags Source 
Show ProfFlags Source 
Show CCFlags Source 
Show DebugFlags Source 
Show MiscFlags Source 
Show ConcFlags Source 
Show GCFlags Source 
Show SomeSymbol Source 
Show SomeNat Source 
Show SrcLoc Source 
Show StaticPtrInfo Source 
Show Void Source 
Show a => Show [a] Source 

Methods

showsPrec :: Int -> [a] -> ShowS Source

show :: [a] -> String Source

showList :: [[a]] -> ShowS Source

(Integral a, Show a) => Show (Ratio a) Source 
Show (Ptr a) Source 

Methods

showsPrec :: Int -> Ptr a -> ShowS Source

show :: Ptr a -> String Source

showList :: [Ptr a] -> ShowS Source

Show (FunPtr a) Source 
Show (U1 p) Source 

Methods

showsPrec :: Int -> U1 p -> ShowS Source

show :: U1 p -> String Source

showList :: [U1 p] -> ShowS Source

Show p => Show (Par1 p) Source 
Show a => Show (Maybe a) Source 
Show a => Show (Down a) Source 
Show a => Show (Last a) Source 
Show a => Show (First a) Source 
Show a => Show (Product a) Source 
Show a => Show (Sum a) Source 

Methods

showsPrec :: Int -> Sum a -> ShowS Source

show :: Sum a -> String Source

showList :: [Sum a] -> ShowS Source

Show a => Show (Dual a) Source 
Show (ForeignPtr a) Source 
Show a => Show (ZipList a) Source 
Show a => Show (Complex a) Source 
HasResolution a => Show (Fixed a) Source 
Show a => Show (Identity a) Source

This instance would be equivalent to the derived instances of the Identity newtype if the runIdentity field were removed

(Show a, Show b) => Show (Either a b) Source 

Methods

showsPrec :: Int -> Either a b -> ShowS Source

show :: Either a b -> String Source

showList :: [Either a b] -> ShowS Source

Show (f p) => Show (Rec1 f p) Source 

Methods

showsPrec :: Int -> Rec1 f p -> ShowS Source

show :: Rec1 f p -> String Source

showList :: [Rec1 f p] -> ShowS Source

(Show a, Show b) => Show (a, b) Source 

Methods

showsPrec :: Int -> (a, b) -> ShowS Source

show :: (a, b) -> String Source

showList :: [(a, b)] -> ShowS Source

Show (ST s a) Source 

Methods

showsPrec :: Int -> ST s a -> ShowS Source

show :: ST s a -> String Source

showList :: [ST s a] -> ShowS Source

Show (Proxy k s) Source 

Methods

showsPrec :: Int -> Proxy k s -> ShowS Source

show :: Proxy k s -> String Source

showList :: [Proxy k s] -> ShowS Source

Show a => Show (Const a b) Source 

Methods

showsPrec :: Int -> Const a b -> ShowS Source

show :: Const a b -> String Source

showList :: [Const a b] -> ShowS Source

Show c => Show (K1 i c p) Source 

Methods

showsPrec :: Int -> K1 i c p -> ShowS Source

show :: K1 i c p -> String Source

showList :: [K1 i c p] -> ShowS Source

(Show (f p), Show (g p)) => Show ((:+:) f g p) Source 

Methods

showsPrec :: Int -> (:+:) f g p -> ShowS Source

show :: (:+:) f g p -> String Source

showList :: [(:+:) f g p] -> ShowS Source

(Show (f p), Show (g p)) => Show ((:*:) f g p) Source 

Methods

showsPrec :: Int -> (:*:) f g p -> ShowS Source

show :: (:*:) f g p -> String Source

showList :: [(:*:) f g p] -> ShowS Source

Show (f (g p)) => Show ((:.:) f g p) Source 

Methods

showsPrec :: Int -> (:.:) f g p -> ShowS Source

show :: (:.:) f g p -> String Source

showList :: [(:.:) f g p] -> ShowS Source

(Show a, Show b, Show c) => Show (a, b, c) Source 

Methods

showsPrec :: Int -> (a, b, c) -> ShowS Source

show :: (a, b, c) -> String Source

showList :: [(a, b, c)] -> ShowS Source

Show ((:~:) k a b) Source 

Methods

showsPrec :: Int -> (:~:) k a b -> ShowS Source

show :: (:~:) k a b -> String Source

showList :: [(:~:) k a b] -> ShowS Source

Show (Coercion k a b) Source 

Methods

showsPrec :: Int -> Coercion k a b -> ShowS Source

show :: Coercion k a b -> String Source

showList :: [Coercion k a b] -> ShowS Source

Show (f a) => Show (Alt k f a) Source 

Methods

showsPrec :: Int -> Alt k f a -> ShowS Source

show :: Alt k f a -> String Source

showList :: [Alt k f a] -> ShowS Source

Show (f p) => Show (M1 i c f p) Source 

Methods

showsPrec :: Int -> M1 i c f p -> ShowS Source

show :: M1 i c f p -> String Source

showList :: [M1 i c f p] -> ShowS Source

(Show a, Show b, Show c, Show d) => Show (a, b, c, d) Source 

Methods

showsPrec :: Int -> (a, b, c, d) -> ShowS Source

show :: (a, b, c, d) -> String Source

showList :: [(a, b, c, d)] -> ShowS Source

(Show a, Show b, Show c, Show d, Show e) => Show (a, b, c, d, e) Source 

Methods

showsPrec :: Int -> (a, b, c, d, e) -> ShowS Source

show :: (a, b, c, d, e) -> String Source

showList :: [(a, b, c, d, e)] -> ShowS Source

(Show a, Show b, Show c, Show d, Show e, Show f) => Show (a, b, c, d, e, f) Source 

Methods

showsPrec :: Int -> (a, b, c, d, e, f) -> ShowS Source

show :: (a, b, c, d, e, f) -> String Source

showList :: [(a, b, c, d, e, f)] -> ShowS Source

(Show a, Show b, Show c, Show d, Show e, Show f, Show g) => Show (a, b, c, d, e, f, g) Source 

Methods

showsPrec :: Int -> (a, b, c, d, e, f, g) -> ShowS Source

show :: (a, b, c, d, e, f, g) -> String Source

showList :: [(a, b, c, d, e, f, g)] -> ShowS Source

(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) Source 

Methods

showsPrec :: Int -> (a, b, c, d, e, f, g, h) -> ShowS Source

show :: (a, b, c, d, e, f, g, h) -> String Source

showList :: [(a, b, c, d, e, f, g, h)] -> ShowS Source

(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) Source 

Methods

showsPrec :: Int -> (a, b, c, d, e, f, g, h, i) -> ShowS Source

show :: (a, b, c, d, e, f, g, h, i) -> String Source

showList :: [(a, b, c, d, e, f, g, h, i)] -> ShowS Source

(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) Source 

Methods

showsPrec :: Int -> (a, b, c, d, e, f, g, h, i, j) -> ShowS Source

show :: (a, b, c, d, e, f, g, h, i, j) -> String Source

showList :: [(a, b, c, d, e, f, g, h, i, j)] -> ShowS Source

(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) Source 

Methods

showsPrec :: Int -> (a, b, c, d, e, f, g, h, i, j, k) -> ShowS Source

show :: (a, b, c, d, e, f, g, h, i, j, k) -> String Source

showList :: [(a, b, c, d, e, f, g, h, i, j, k)] -> ShowS Source

(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) Source 

Methods

showsPrec :: Int -> (a, b, c, d, e, f, g, h, i, j, k, l) -> ShowS Source

show :: (a, b, c, d, e, f, g, h, i, j, k, l) -> String Source

showList :: [(a, b, c, d, e, f, g, h, i, j, k, l)] -> ShowS Source

(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) Source 

Methods

showsPrec :: Int -> (a, b, c, d, e, f, g, h, i, j, k, l, m) -> ShowS Source

show :: (a, b, c, d, e, f, g, h, i, j, k, l, m) -> String Source

showList :: [(a, b, c, d, e, f, g, h, i, j, k, l, m)] -> ShowS Source

(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) Source 

Methods

showsPrec :: Int -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> ShowS Source

show :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> String Source

showList :: [(a, b, c, d, e, f, g, h, i, j, k, l, m, n)] -> ShowS Source

(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) Source 

Methods

showsPrec :: Int -> (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> ShowS Source

show :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> String Source

showList :: [(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o)] -> ShowS Source

shows :: Show a => a -> ShowS Source

equivalent to showsPrec with a precedence of 0.

showChar :: Char -> ShowS Source

utility function converting a Char to a show function that simply prepends the character unchanged.

showString :: String -> ShowS Source

utility function converting a String to a show function that simply prepends the string unchanged.

showParen :: Bool -> ShowS -> ShowS Source

utility function that surrounds the inner show function with parentheses when the Bool parameter is True.

showListWith :: (a -> ShowS) -> [a] -> ShowS Source

Show a list (using square brackets and commas), given a function for showing elements.