Copyright | (c) The University of Glasgow 2001 |
---|---|
License | BSD-style (see the file libraries/base/LICENSE) |
Maintainer | libraries@haskell.org |
Stability | provisional |
Portability | portable |
Safe Haskell | Safe |
Language | Haskell2010 |
Converting values to readable strings:
the Show
class and associated functions.
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
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 thand
(associativity is ignored). Thus, ifd
is0
then the result is never surrounded in parentheses; ifd
is11
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,
produces the stringshow
(Leaf 1 :^: Leaf 2 :^: Leaf 3)"Leaf 1 :^: (Leaf 2 :^: Leaf 3)"
.
:: Int | the operator precedence of the enclosing
context (a number from |
-> a | the value to be converted to a |
-> 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.
Instances
Show Bool # | Since: base-2.1 |
Show Char # | Since: base-2.1 |
Show Double # | Since: base-2.1 |
Show Float # | Since: base-2.1 |
Show Int # | Since: base-2.1 |
Show Int8 # | Since: base-2.1 |
Show Int16 # | Since: base-2.1 |
Show Int32 # | Since: base-2.1 |
Show Int64 # | Since: base-2.1 |
Show Integer # | Since: base-2.1 |
Show Natural # | Since: base-4.8.0.0 |
Show Ordering # | Since: base-2.1 |
Show Word # | Since: base-2.1 |
Show Word8 # | Since: base-2.1 |
Show Word16 # | Since: base-2.1 |
Show Word32 # | Since: base-2.1 |
Show Word64 # | Since: base-2.1 |
Show RuntimeRep # | Since: base-4.11.0.0 |
Show VecCount # | Since: base-4.11.0.0 |
Show VecElem # | Since: base-4.11.0.0 |
Show CallStack # | Since: base-4.9.0.0 |
Show SomeTypeRep # | Since: base-4.10.0.0 |
Defined in Data.Typeable.Internal | |
Show () # | Since: base-2.1 |
Show TyCon # | Since: base-2.1 |
Show Module # | Since: base-4.9.0.0 |
Show TrName # | Since: base-4.9.0.0 |
Show KindRep # | |
Show TypeLitSort # | Since: base-4.11.0.0 |
Show SomeException # | Since: base-3.0 |
Defined in GHC.Exception.Type | |
Show SrcLoc # | Since: base-4.9.0.0 |
Show Version # | Since: base-2.1 |
Show GeneralCategory # | Since: base-2.1 |
Defined in GHC.Unicode | |
Show Number # | Since: base-4.6.0.0 |
Show Lexeme # | Since: base-2.1 |
Show Fingerprint # | Since: base-4.7.0.0 |
Defined in GHC.Fingerprint.Type | |
Show IOMode # | Since: base-4.2.0.0 |
Show SomeNat # | Since: base-4.7.0.0 |
Show SomeSymbol # | Since: base-4.7.0.0 |
Defined in GHC.TypeLits | |
Show IntPtr # | |
Show WordPtr # | |
Show CUIntMax # | |
Show CIntMax # | |
Show CUIntPtr # | |
Show CIntPtr # | |
Show CSUSeconds # | |
Defined in Foreign.C.Types | |
Show CUSeconds # | |
Show CTime # | |
Show CClock # | |
Show CSigAtomic # | |
Defined in Foreign.C.Types | |
Show CWchar # | |
Show CSize # | |
Show CPtrdiff # | |
Show CDouble # | |
Show CFloat # | |
Show CBool # | |
Show CULLong # | |
Show CLLong # | |
Show CULong # | |
Show CLong # | |
Show CUInt # | |
Show CInt # | |
Show CUShort # | |
Show CShort # | |
Show CUChar # | |
Show CSChar # | |
Show CChar # | |
Show DecidedStrictness # | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
Show SourceStrictness # | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
Show SourceUnpackedness # | Since: base-4.9.0.0 |
Defined in GHC.Generics | |
Show Associativity # | Since: base-4.6.0.0 |
Defined in GHC.Generics | |
Show Fixity # | Since: base-4.6.0.0 |
Show Any # | Since: base-2.1 |
Show All # | Since: base-2.1 |
Show Lifetime # | Since: base-4.8.1.0 |
Show Event # | Since: base-4.4.0.0 |
Show ArithException # | Since: base-4.0.0.0 |
Defined in GHC.Exception.Type | |
Show ErrorCall # | Since: base-4.0.0.0 |
Show FileLockingNotSupported # | Since: base-4.10.0.0 |
Defined in GHC.IO.Handle.Lock.Common | |
Show IOException # | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
Show MaskingState # | Since: base-4.3.0.0 |
Show CodingProgress # | Since: base-4.4.0.0 |
Defined in GHC.IO.Encoding.Types | |
Show TextEncoding # | Since: base-4.3.0.0 |
Defined in GHC.IO.Encoding.Types | |
Show SeekMode # | Since: base-4.2.0.0 |
Show NewlineMode # | Since: base-4.3.0.0 |
Defined in GHC.IO.Handle.Types | |
Show Newline # | Since: base-4.3.0.0 |
Show BufferMode # | Since: base-4.2.0.0 |
Defined in GHC.IO.Handle.Types | |
Show HandleType # | Since: base-4.1.0.0 |
Defined in GHC.IO.Handle.Types | |
Show Handle # | Since: base-4.1.0.0 |
Show IOErrorType # | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
Show ExitCode # | |
Show FixIOException # | Since: base-4.11.0.0 |
Defined in GHC.IO.Exception | |
Show ArrayException # | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
Show AsyncException # | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
Show SomeAsyncException # | Since: base-4.7.0.0 |
Defined in GHC.IO.Exception | |
Show AssertionFailed # | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
Show CompactionFailed # | Since: base-4.10.0.0 |
Defined in GHC.IO.Exception | |
Show AllocationLimitExceeded # | Since: base-4.7.1.0 |
Defined in GHC.IO.Exception | |
Show Deadlock # | Since: base-4.1.0.0 |
Show BlockedIndefinitelyOnSTM # | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
Show BlockedIndefinitelyOnMVar # | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
Show CodingFailureMode # | Since: base-4.4.0.0 |
Defined in GHC.IO.Encoding.Failure | |
Show Fd # | |
Show CNfds # | |
Show CSocklen # | |
Show CTimer # | |
Show CKey # | |
Show CId # | |
Show CFsFilCnt # | |
Show CFsBlkCnt # | |
Show CClockId # | |
Show CBlkCnt # | |
Show CBlkSize # | |
Show CRLim # | |
Show CTcflag # | |
Show CSpeed # | |
Show CCc # | |
Show CUid # | |
Show CNlink # | |
Show CGid # | |
Show CSsize # | |
Show CPid # | |
Show COff # | |
Show CMode # | |
Show CIno # | |
Show CDev # | |
Show RTSFlags # | Since: base-4.8.0.0 |
Show ParFlags # | Since: base-4.8.0.0 |
Show TickyFlags # | Since: base-4.8.0.0 |
Defined in GHC.RTS.Flags | |
Show TraceFlags # | Since: base-4.8.0.0 |
Defined in GHC.RTS.Flags | |
Show DoTrace # | Since: base-4.8.0.0 |
Show ProfFlags # | Since: base-4.8.0.0 |
Show DoHeapProfile # | Since: base-4.8.0.0 |
Defined in GHC.RTS.Flags | |
Show CCFlags # | Since: base-4.8.0.0 |
Show DoCostCentres # | Since: base-4.8.0.0 |
Defined in GHC.RTS.Flags | |
Show DebugFlags # | Since: base-4.8.0.0 |
Defined in GHC.RTS.Flags | |
Show MiscFlags # | Since: base-4.8.0.0 |
Show ConcFlags # | Since: base-4.8.0.0 |
Show GCFlags # | Since: base-4.8.0.0 |
Show IoSubSystem # | |
Defined in GHC.RTS.Flags | |
Show GiveGCStats # | Since: base-4.8.0.0 |
Defined in GHC.RTS.Flags | |
Show Dynamic # | Since: base-2.1 |
Show ThreadStatus # | Since: base-4.3.0.0 |
Defined in GHC.Conc.Sync | |
Show BlockReason # | Since: base-4.3.0.0 |
Defined in GHC.Conc.Sync | |
Show ThreadId # | Since: base-4.2.0.0 |
Show NestedAtomically # | Since: base-4.0 |
Defined in Control.Exception.Base | |
Show NonTermination # | Since: base-4.0 |
Defined in Control.Exception.Base | |
Show TypeError # | Since: base-4.9.0.0 |
Show NoMethodError # | Since: base-4.0 |
Defined in Control.Exception.Base | |
Show RecUpdError # | Since: base-4.0 |
Defined in Control.Exception.Base | |
Show RecConError # | Since: base-4.0 |
Defined in Control.Exception.Base | |
Show RecSelError # | Since: base-4.0 |
Defined in Control.Exception.Base | |
Show PatternMatchFail # | Since: base-4.0 |
Defined in Control.Exception.Base | |
Show FdKey # | Since: base-4.4.0.0 |
Show FD # | Since: base-4.1.0.0 |
Show HandlePosn # | Since: base-4.1.0.0 |
Defined in GHC.IO.Handle | |
Show StaticPtrInfo # | Since: base-4.8.0.0 |
Defined in GHC.StaticPtr | |
Show ByteOrder # | Since: base-4.11.0.0 |
Show GCDetails # | Since: base-4.10.0.0 |
Show RTSStats # | Since: base-4.10.0.0 |
Show Timeout # | Since: base-4.0 |
Show Fixity # | Since: base-4.0.0.0 |
Show ConstrRep # | Since: base-4.0.0.0 |
Show DataRep # | Since: base-4.0.0.0 |
Show Constr # | Since: base-4.0.0.0 |
Show DataType # | Since: base-4.0.0.0 |
Show Void # | Since: base-4.8.0.0 |
Show a => Show [a] # | Since: base-2.1 |
Show a => Show (Maybe a) # | Since: base-2.1 |
Show a => Show (Ratio a) # | Since: base-2.0.1 |
Show (Ptr a) # | Since: base-2.1 |
Show (FunPtr a) # | Since: base-2.1 |
Show p => Show (Par1 p) # | Since: base-4.7.0.0 |
Show a => Show (a) # | Since: base-4.15 |
Show a => Show (NonEmpty a) # | Since: base-4.11.0.0 |
Show a => Show (Down a) # | This instance would be equivalent to the derived instances of the
Since: base-4.7.0.0 |
Show a => Show (Product a) # | Since: base-2.1 |
Show a => Show (Sum a) # | Since: base-2.1 |
Show a => Show (Dual a) # | Since: base-2.1 |
Show a => Show (Last a) # | Since: base-2.1 |
Show a => Show (First a) # | Since: base-2.1 |
Show (ForeignPtr a) # | Since: base-2.1 |
Defined in GHC.ForeignPtr | |
Show a => Show (Identity a) # | This instance would be equivalent to the derived instances of the
Since: base-4.8.0.0 |
Show a => Show (ZipList a) # | Since: base-4.7.0.0 |
Show a => Show (Option a) # | Since: base-4.9.0.0 |
Show m => Show (WrappedMonoid m) # | Since: base-4.9.0.0 |
Defined in Data.Semigroup | |
Show a => Show (Last a) # | Since: base-4.9.0.0 |
Show a => Show (First a) # | Since: base-4.9.0.0 |
Show a => Show (Max a) # | Since: base-4.9.0.0 |
Show a => Show (Min a) # | Since: base-4.9.0.0 |
Show a => Show (Complex a) # | Since: base-2.1 |
Show (a -> b) # | Since: base-2.1 |
(Show a, Show b) => Show (Either a b) # | Since: base-3.0 |
Show (V1 p) # | Since: base-4.9.0.0 |
Show (U1 p) # | Since: base-4.9.0.0 |
Show (TypeRep a) # | |
(Show a, Show b) => Show (a, b) # | Since: base-2.1 |
Show (ST s a) # | Since: base-2.1 |
(Ix a, Show a, Show b) => Show (Array a b) # | Since: base-2.1 |
Show (Proxy s) # | Since: base-4.7.0.0 |
(Show a, Show b) => Show (Arg a b) # | Since: base-4.9.0.0 |
HasResolution a => Show (Fixed a) # | Since: base-2.1 |
Show (f p) => Show (Rec1 f p) # | Since: base-4.7.0.0 |
Show (URec Word p) # | Since: base-4.9.0.0 |
Show (URec Int p) # | Since: base-4.9.0.0 |
Show (URec Float p) # | |
Show (URec Double p) # | Since: base-4.9.0.0 |
Show (URec Char p) # | Since: base-4.9.0.0 |
(Show a, Show b, Show c) => Show (a, b, c) # | Since: base-2.1 |
Show (a :~: b) # | Since: base-4.7.0.0 |
Show (Coercion a b) # | Since: base-4.7.0.0 |
Show (f a) => Show (Alt f a) # | Since: base-4.8.0.0 |
Show (f a) => Show (Ap f a) # | Since: base-4.12.0.0 |
Show a => Show (Const a b) # | This instance would be equivalent to the derived instances of the
Since: base-4.8.0.0 |
Show c => Show (K1 i c p) # | Since: base-4.7.0.0 |
(Show (f p), Show (g p)) => Show ((f :+: g) p) # | Since: base-4.7.0.0 |
(Show (f p), Show (g p)) => Show ((f :*: g) p) # | Since: base-4.7.0.0 |
(Show a, Show b, Show c, Show d) => Show (a, b, c, d) # | Since: base-2.1 |
Show (a :~~: b) # | Since: base-4.10.0.0 |
(Show1 f, Show1 g, Show a) => Show (Sum f g a) # | Since: base-4.9.0.0 |
(Show1 f, Show1 g, Show a) => Show (Product f g a) # | Since: base-4.9.0.0 |
Show (f p) => Show (M1 i c f p) # | Since: base-4.7.0.0 |
Show (f (g p)) => Show ((f :.: g) p) # | Since: base-4.7.0.0 |
(Show a, Show b, Show c, Show d, Show e) => Show (a, b, c, d, e) # | Since: base-2.1 |
(Show1 f, Show1 g, Show a) => Show (Compose f g a) # | Since: base-4.9.0.0 |
(Show a, Show b, Show c, Show d, Show e, Show f) => Show (a, b, c, d, e, f) # | Since: base-2.1 |
(Show a, Show b, Show c, Show d, Show e, Show f, Show g) => Show (a, b, c, d, e, f, g) # | Since: base-2.1 |
(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) # | Since: base-2.1 |
(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) # | Since: base-2.1 |
(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) # | Since: base-2.1 |
(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) # | Since: base-2.1 |
(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) # | Since: base-2.1 |
(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) # | Since: base-2.1 |
(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) # | Since: base-2.1 |
(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) # | Since: base-2.1 |
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.
showListWith :: (a -> ShowS) -> [a] -> ShowS Source #
Show a list (using square brackets and commas), given a function for showing elements.