| Copyright | (c) The University of Glasgow 1992-2002 |
|---|---|
| License | see libraries/base/LICENSE |
| Maintainer | ghc-devs@haskell.org |
| Stability | internal |
| Portability | non-portable (GHC Extensions) |
| Safe Haskell | Safe |
| Language | Haskell2010 |
GHC.Show
Description
The Show class, and related operations.
Synopsis
- class Show a where
- type ShowS = String -> String
- shows :: Show a => a -> ShowS
- showChar :: Char -> ShowS
- showString :: String -> ShowS
- showMultiLineString :: String -> [String]
- showParen :: Bool -> ShowS -> ShowS
- showList__ :: (a -> ShowS) -> [a] -> ShowS
- showCommaSpace :: ShowS
- showSpace :: ShowS
- showLitChar :: Char -> ShowS
- showLitString :: String -> ShowS
- protectEsc :: (Char -> Bool) -> ShowS -> ShowS
- intToDigit :: Int -> Char
- showSignedInt :: Int -> Int -> ShowS
- appPrec :: Int
- appPrec1 :: Int
- asciiTab :: [String]
Documentation
Conversion of values to readable String s.
Derived instances of Show have the following properties, which
are compatible with derived instances of Read :
- The result of
showis a syntactically correct Haskell expression containing only constants, given the fixity declarations in force at the point where the type is declared. It contains only the constructor names defined in the data type, parentheses, and spaces. When labelled constructor fields are used, braces, commas, field names, and equal signs are also used. - If the constructor is defined to be an infix operator, then
showsPrecwill produce infix applications of the constructor. - the representation will be enclosed in parentheses if the
precedence of the top-level constructor in
xis less thand(associativity is ignored). Thus, ifdis0then the result is never surrounded in parentheses; ifdis11it is always surrounded in parentheses, unless it is an atomic expression. - If the constructor is defined using record syntax, then
showwill produce the record-syntax form, with the fields given in the same order as the original declaration.
For example, given the declarations
infixr 5 :^: data Tree a = Leaf a | Tree a :^: Tree a
the derived instance of Show is equivalent to
instance (Show a) => Show (Tree a) where showsPrec d (Leaf m) = showParen (d > app_prec) $ showString "Leaf " . showsPrec (app_prec+1) m where app_prec = 10 showsPrec d (u :^: v) = showParen (d > up_prec) $ showsPrec (up_prec+1) u . showString " :^: " . showsPrec (up_prec+1) v where up_prec = 5
Note that right-associativity of :^: is ignored. For example,
show(Leaf 1 :^: Leaf 2 :^: Leaf 3)"Leaf 1 :^: (Leaf 2 :^: Leaf 3)".
Methods
Arguments
the operator precedence of the enclosing
context (a number from 0 to 11).
Function application has precedence 10.
the value to be converted to a 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.
Instances
Instances details
Instance details
Defined in GHC.Internal.ClosureTypes
Instance details
Defined in GHC.Internal.Conc.Sync
Instance details
Defined in GHC.Internal.Conc.Sync
Instance details
Defined in GHC.Internal.Control.Exception.Base
Instance details
Defined in GHC.Internal.Control.Exception.Base
Instance details
Defined in GHC.Internal.Control.Exception.Base
Instance details
Defined in GHC.Internal.Control.Exception.Base
Instance details
Defined in GHC.Internal.Control.Exception.Base
Instance details
Defined in GHC.Internal.Control.Exception.Base
Instance details
Defined in GHC.Internal.Control.Exception.Base
Instance details
Defined in GHC.Internal.Control.Exception.Base
Instance details
Defined in GHC.Internal.Data.Typeable.Internal
Instance details
Defined in GHC.Internal.Exception.Type
Instance details
Defined in GHC.Internal.Exception.Type
Instance details
Defined in GHC.Internal.Exception.Type
Instance details
Defined in GHC.Internal.Fingerprint.Type
Instance details
Defined in GHC.Internal.Foreign.C.Types
Instance details
Defined in GHC.Internal.Foreign.C.Types
Instance details
Defined in GHC.Internal.ForeignSrcLang
Instance details
Defined in GHC.Internal.Generics
Instance details
Defined in GHC.Internal.Generics
Instance details
Defined in GHC.Internal.Generics
Instance details
Defined in GHC.Internal.Generics
Instance details
Defined in GHC.Internal.IO
Instance details
Defined in GHC.Internal.IO.Encoding.Failure
Instance details
Defined in GHC.Internal.IO.Encoding.Types
Instance details
Defined in GHC.Internal.IO.Encoding.Types
Instance details
Defined in GHC.Internal.IO.Exception
Instance details
Defined in GHC.Internal.IO.Exception
Instance details
Defined in GHC.Internal.IO.Exception
Instance details
Defined in GHC.Internal.IO.Exception
Instance details
Defined in GHC.Internal.IO.Exception
Instance details
Defined in GHC.Internal.IO.Exception
Instance details
Defined in GHC.Internal.IO.Exception
Instance details
Defined in GHC.Internal.IO.Exception
Instance details
Defined in GHC.Internal.IO.Exception
Instance details
Defined in GHC.Internal.IO.Exception
Instance details
Defined in GHC.Internal.IO.Exception
Instance details
Defined in GHC.Internal.IO.Handle
Instance details
Defined in GHC.Internal.IO.Handle.Lock.Common
Instance details
Defined in GHC.Internal.IO.Handle.Types
Instance details
Defined in GHC.Internal.IO.Handle.Types
Instance details
Defined in GHC.Internal.IO.Handle.Types
Instance details
Defined in GHC.Internal.IO.SubSystem
Instance details
Defined in GHC.Internal.RTS.Flags
Instance details
Defined in GHC.Internal.RTS.Flags
Instance details
Defined in GHC.Internal.RTS.Flags
Instance details
Defined in GHC.Internal.RTS.Flags
Instance details
Defined in GHC.Internal.RTS.Flags
Instance details
Defined in GHC.Internal.RTS.Flags
Instance details
Defined in GHC.Internal.RTS.Flags
Instance details
Defined in GHC.Internal.Real
Instance details
Defined in GHC.Internal.Stack.CloneStack
Instance details
Defined in GHC.Internal.StaticPtr
Instance details
Defined in GHC.Internal.TH.Syntax
Instance details
Defined in GHC.Internal.TH.Syntax
Instance details
Defined in GHC.Internal.TH.Syntax
Instance details
Defined in GHC.Internal.TH.Syntax
Instance details
Defined in GHC.Internal.TH.Syntax
Instance details
Defined in GHC.Internal.TH.Syntax
Instance details
Defined in GHC.Internal.TH.Syntax
Instance details
Defined in GHC.Internal.TH.Syntax
Instance details
Defined in GHC.Internal.TH.Syntax
Instance details
Defined in GHC.Internal.TH.Syntax
Instance details
Defined in GHC.Internal.TH.Syntax
Instance details
Defined in GHC.Internal.TH.Syntax
Instance details
Defined in GHC.Internal.TH.Syntax
Instance details
Defined in GHC.Internal.TH.Syntax
Instance details
Defined in GHC.Internal.TypeLits
Instance details
Defined in GHC.Internal.Unicode
Instance details
Defined in GHC.Internal.Show
Instance details
Defined in GHC.Internal.Show
Instance details
Defined in Data.Semigroup
This instance would be equivalent to the derived instances of the
Identity newtype if the runIdentity field were removed
Since: base-4.8.0.0
This instance would be equivalent to the derived instances of the
Down newtype if the getDown field were removed
Since: base-4.7.0.0
Instance details
Defined in GHC.Internal.Exception.Type
Instance details
Defined in GHC.Internal.Exception.Type
Instance details
Defined in GHC.Internal.ForeignPtr
This instance would be equivalent to the derived instances of the
Const newtype if the getConst field were removed
Since: base-4.8.0.0
Since: base-2.1
Since: base-2.1
Since: base-2.1
Since: base-2.1
Since: base-2.1
Since: base-2.1
Since: base-2.1
Since: base-2.1
Since: base-2.1
Show support code
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.
showMultiLineString :: String -> [String] Source #
Like showLitString (expand escape characters using Haskell
escape conventions), but
* break the string into multiple lines
* wrap the entire thing in double quotes
Example: showMultiLineString "hellongoodbyenblah"
returns [""hello\n\", "\goodbyen\", "\blah""]
showList__ :: (a -> ShowS) -> [a] -> ShowS Source #
showLitChar :: Char -> ShowS Source #
Convert a character to a string using only printable characters, using Haskell source-language escape conventions. For example:
showLitChar '\n' s = "\\n" ++ s
showLitString :: String -> ShowS Source #
Same as showLitChar , but for strings
It converts the string to a string using Haskell escape conventions
for non-printable characters. Does not add double-quotes around the
whole thing; the caller should do that.
The main difference from showLitChar (apart from the fact that the
argument is a string not a list) is that we must escape double-quotes
intToDigit :: Int -> Char Source #