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 Text.Read.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)".
| | Methods | showsPrec | :: 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 | |
| | show :: a -> String | | showList :: [a] -> ShowS |
| | 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 TyCon | Show TypeRep | Show Dynamic | Show Lexeme | Show CChar | Show CSChar | Show CUChar | Show CShort | Show CUShort | Show CInt | Show CUInt | Show CLong | Show CULong | Show CLLong | Show CULLong | Show CFloat | Show CDouble | Show CLDouble | Show CPtrdiff | Show CSize | Show CWchar | Show CSigAtomic | Show CClock | Show CTime | Show CIntPtr | Show CUIntPtr | Show CIntMax | Show CUIntMax | Show IOMode | Show BufferMode | Show ExitCode | Show AsyncException | Show ArrayException | Show ArithException | Show IOErrorType | Show Handle | Show IOException | Show Exception | Show HandleType | Show GeneralCategory | Show HashData | Show IntPtr | Show WordPtr | Show CSsize | Show CCc | Show CSpeed | Show CTcflag | Show CRLim | Show Fd | Show CNlink | Show CUid | Show CGid | Show CDev | Show CIno | Show CMode | Show COff | Show CPid | Show ThreadId | Show SeekMode | Show HandlePosn | Show All | Show Any | Show Version | Show Fixity | Show ConstrRep | Show DataRep | Show DataType | Show Constr | Show a => Show ([] a) | Integral a => Show (Ratio a) | Show (Ptr a) | Show (FunPtr a) | Show a => Show ([::] a) | Show a => Show (Maybe a) | Show (ForeignPtr 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) | HasResolution a => Show (Fixed a) | RealFloat a => Show (Complex a) | Show (a -> b) | (Show a, Show b) => Show (Either a b) | (Show a, Show b) => Show ((,) a b) | Show (ST s a) | (Ix a, Show a, Show b) => Show (Array a b) | (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) |
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