{-# LANGUAGE Safe #-}------------------------------------------------------------------------------- |-- Module : Data.Functor.Classes-- Copyright : (c) Ross Paterson 2013-- License : BSD-style (see the file LICENSE)---- Maintainer : libraries@haskell.org-- Stability : experimental-- Portability : portable---- Liftings of the Prelude classes 'Eq', 'Ord', 'Read' and 'Show' to-- unary and binary type constructors.---- These classes are needed to express the constraints on arguments of-- transformers in portable Haskell. Thus for a new transformer @T@,-- one might write instances like---- > instance (Eq1 f) => Eq1 (T f) where ...-- > instance (Ord1 f) => Ord1 (T f) where ...-- > instance (Read1 f) => Read1 (T f) where ...-- > instance (Show1 f) => Show1 (T f) where ...---- If these instances can be defined, defining instances of the base-- classes is mechanical:---- > instance (Eq1 f, Eq a) => Eq (T f a) where (==) = eq1-- > instance (Ord1 f, Ord a) => Ord (T f a) where compare = compare1-- > instance (Read1 f, Read a) => Read (T f a) where-- > readPrec = readPrec1-- > readListPrec = readListPrecDefault-- > instance (Show1 f, Show a) => Show (T f a) where showsPrec = showsPrec1---- @since 4.9.0.0-----------------------------------------------------------------------------moduleData.Functor.Classes(-- * Liftings of Prelude classes-- ** For unary constructorsEq1 (..),eq1 ,Ord1 (..),compare1 ,Read1 (..),readsPrec1 ,readPrec1 ,liftReadListDefault ,liftReadListPrecDefault ,Show1 (..),showsPrec1 ,-- ** For binary constructorsEq2 (..),eq2 ,Ord2 (..),compare2 ,Read2 (..),readsPrec2 ,readPrec2 ,liftReadList2Default ,liftReadListPrec2Default ,Show2 (..),showsPrec2 ,-- * Helper functions-- $examplereadsData ,readData ,readsUnaryWith ,readUnaryWith ,readsBinaryWith ,readBinaryWith ,showsUnaryWith ,showsBinaryWith ,-- ** Obsolete helpersreadsUnary ,readsUnary1 ,readsBinary1 ,showsUnary ,showsUnary1 ,showsBinary1 ,)whereimportControl.Applicative (Alternative ((<|> )),Const (Const ))importData.Functor.Identity (Identity (Identity ))importData.Proxy (Proxy (Proxy ))importData.List.NonEmpty (NonEmpty (..))importData.Monoid (mappend )importData.Ord (Down (Down ))importGHC.Read (expectP ,list ,paren )importText.ParserCombinators.ReadPrec (ReadPrec ,readPrec_to_S ,readS_to_Prec )importText.Read (Read (..),parens ,prec ,step )importText.Read.Lex (Lexeme (..))importText.Show (showListWith )-- | Lifting of the 'Eq' class to unary type constructors.---- @since 4.9.0.0classEq1 f where-- | Lift an equality test through the type constructor.---- The function will usually be applied to an equality function,-- but the more general type ensures that the implementation uses-- it to compare elements of the first container with elements of-- the second.---- @since 4.9.0.0liftEq ::(a ->b ->Bool)->f a ->f b ->Bool-- | Lift the standard @('==')@ function through the type constructor.---- @since 4.9.0.0eq1::(Eq1 f ,Eqa )=>f a ->f a ->Booleq1 =liftEq (==)-- | Lifting of the 'Ord' class to unary type constructors.---- @since 4.9.0.0class(Eq1 f )=>Ord1 f where-- | Lift a 'compare' function through the type constructor.---- The function will usually be applied to a comparison function,-- but the more general type ensures that the implementation uses-- it to compare elements of the first container with elements of-- the second.---- @since 4.9.0.0liftCompare ::(a ->b ->Ordering)->f a ->f b ->Ordering-- | Lift the standard 'compare' function through the type constructor.---- @since 4.9.0.0compare1::(Ord1 f ,Orda )=>f a ->f a ->Orderingcompare1 =liftCompare compare-- | Lifting of the 'Read' class to unary type constructors.---- Both 'liftReadsPrec' and 'liftReadPrec' exist to match the interface-- provided in the 'Read' type class, but it is recommended to implement-- 'Read1' instances using 'liftReadPrec' as opposed to 'liftReadsPrec', since-- the former is more efficient than the latter. For example:---- @-- instance 'Read1' T where-- 'liftReadPrec' = ...-- 'liftReadListPrec' = 'liftReadListPrecDefault'-- @---- For more information, refer to the documentation for the 'Read' class.---- @since 4.9.0.0classRead1 f where{-# MINIMALliftReadsPrec|liftReadPrec#-}-- | 'readsPrec' function for an application of the type constructor-- based on 'readsPrec' and 'readList' functions for the argument type.---- @since 4.9.0.0liftReadsPrec ::(Int->ReadS a )->ReadS [a ]->Int->ReadS (f a )liftReadsPrec rp rl =readPrec_to_S $ liftReadPrec (readS_to_Prec rp )(readS_to_Prec (const rl ))-- | 'readList' function for an application of the type constructor-- based on 'readsPrec' and 'readList' functions for the argument type.-- The default implementation using standard list syntax is correct-- for most types.---- @since 4.9.0.0liftReadList ::(Int->ReadS a )->ReadS [a ]->ReadS [f a ]liftReadList rp rl =readPrec_to_S (list $ liftReadPrec (readS_to_Prec rp )(readS_to_Prec (const rl )))0-- | 'readPrec' function for an application of the type constructor-- based on 'readPrec' and 'readListPrec' functions for the argument type.---- @since 4.10.0.0liftReadPrec ::ReadPrec a ->ReadPrec [a ]->ReadPrec (f a )liftReadPrec rp rl =readS_to_Prec $ liftReadsPrec (readPrec_to_S rp )(readPrec_to_S rl 0)-- | 'readListPrec' function for an application of the type constructor-- based on 'readPrec' and 'readListPrec' functions for the argument type.---- The default definition uses 'liftReadList'. Instances that define-- 'liftReadPrec' should also define 'liftReadListPrec' as-- 'liftReadListPrecDefault'.---- @since 4.10.0.0liftReadListPrec ::ReadPrec a ->ReadPrec [a ]->ReadPrec [f a ]liftReadListPrec rp rl =readS_to_Prec $ \_->liftReadList (readPrec_to_S rp )(readPrec_to_S rl 0)-- | Lift the standard 'readsPrec' and 'readList' functions through the-- type constructor.---- @since 4.9.0.0readsPrec1::(Read1 f ,Read a )=>Int->ReadS (f a )readsPrec1 =liftReadsPrec readsPrec readList -- | Lift the standard 'readPrec' and 'readListPrec' functions through the-- type constructor.---- @since 4.10.0.0readPrec1::(Read1 f ,Read a )=>ReadPrec (f a )readPrec1 =liftReadPrec readPrec readListPrec -- | A possible replacement definition for the 'liftReadList' method.-- This is only needed for 'Read1' instances where 'liftReadListPrec' isn't-- defined as 'liftReadListPrecDefault'.---- @since 4.10.0.0liftReadListDefault::Read1 f =>(Int->ReadS a )->ReadS [a ]->ReadS [f a ]liftReadListDefault rp rl =readPrec_to_S (liftReadListPrec (readS_to_Prec rp )(readS_to_Prec (const rl )))0-- | A possible replacement definition for the 'liftReadListPrec' method,-- defined using 'liftReadPrec'.---- @since 4.10.0.0liftReadListPrecDefault::Read1 f =>ReadPrec a ->ReadPrec [a ]->ReadPrec [f a ]liftReadListPrecDefault rp rl =list (liftReadPrec rp rl )-- | Lifting of the 'Show' class to unary type constructors.---- @since 4.9.0.0classShow1 f where-- | 'showsPrec' function for an application of the type constructor-- based on 'showsPrec' and 'showList' functions for the argument type.---- @since 4.9.0.0liftShowsPrec ::(Int->a ->ShowS )->([a ]->ShowS )->Int->f a ->ShowS -- | 'showList' function for an application of the type constructor-- based on 'showsPrec' and 'showList' functions for the argument type.-- The default implementation using standard list syntax is correct-- for most types.---- @since 4.9.0.0liftShowList ::(Int->a ->ShowS )->([a ]->ShowS )->[f a ]->ShowS liftShowList sp sl =showListWith (liftShowsPrec sp sl 0)-- | Lift the standard 'showsPrec' and 'showList' functions through the-- type constructor.---- @since 4.9.0.0showsPrec1::(Show1 f ,Show a )=>Int->f a ->ShowS showsPrec1 =liftShowsPrec showsPrec showList -- | Lifting of the 'Eq' class to binary type constructors.---- @since 4.9.0.0classEq2 f where-- | Lift equality tests through the type constructor.---- The function will usually be applied to equality functions,-- but the more general type ensures that the implementation uses-- them to compare elements of the first container with elements of-- the second.---- @since 4.9.0.0liftEq2 ::(a ->b ->Bool)->(c ->d ->Bool)->f a c ->f b d ->Bool-- | Lift the standard @('==')@ function through the type constructor.---- @since 4.9.0.0eq2::(Eq2 f ,Eqa ,Eqb )=>f a b ->f a b ->Booleq2 =liftEq2 (==)(==)-- | Lifting of the 'Ord' class to binary type constructors.---- @since 4.9.0.0class(Eq2 f )=>Ord2 f where-- | Lift 'compare' functions through the type constructor.---- The function will usually be applied to comparison functions,-- but the more general type ensures that the implementation uses-- them to compare elements of the first container with elements of-- the second.---- @since 4.9.0.0liftCompare2 ::(a ->b ->Ordering)->(c ->d ->Ordering)->f a c ->f b d ->Ordering-- | Lift the standard 'compare' function through the type constructor.---- @since 4.9.0.0compare2::(Ord2 f ,Orda ,Ordb )=>f a b ->f a b ->Orderingcompare2 =liftCompare2 comparecompare-- | Lifting of the 'Read' class to binary type constructors.---- Both 'liftReadsPrec2' and 'liftReadPrec2' exist to match the interface-- provided in the 'Read' type class, but it is recommended to implement-- 'Read2' instances using 'liftReadPrec2' as opposed to 'liftReadsPrec2',-- since the former is more efficient than the latter. For example:---- @-- instance 'Read2' T where-- 'liftReadPrec2' = ...-- 'liftReadListPrec2' = 'liftReadListPrec2Default'-- @---- For more information, refer to the documentation for the 'Read' class.-- @since 4.9.0.0classRead2 f where{-# MINIMALliftReadsPrec2|liftReadPrec2#-}-- | 'readsPrec' function for an application of the type constructor-- based on 'readsPrec' and 'readList' functions for the argument types.---- @since 4.9.0.0liftReadsPrec2 ::(Int->ReadS a )->ReadS [a ]->(Int->ReadS b )->ReadS [b ]->Int->ReadS (f a b )liftReadsPrec2 rp1 rl1 rp2 rl2 =readPrec_to_S $ liftReadPrec2 (readS_to_Prec rp1 )(readS_to_Prec (const rl1 ))(readS_to_Prec rp2 )(readS_to_Prec (const rl2 ))-- | 'readList' function for an application of the type constructor-- based on 'readsPrec' and 'readList' functions for the argument types.-- The default implementation using standard list syntax is correct-- for most types.---- @since 4.9.0.0liftReadList2 ::(Int->ReadS a )->ReadS [a ]->(Int->ReadS b )->ReadS [b ]->ReadS [f a b ]liftReadList2 rp1 rl1 rp2 rl2 =readPrec_to_S (list $ liftReadPrec2 (readS_to_Prec rp1 )(readS_to_Prec (const rl1 ))(readS_to_Prec rp2 )(readS_to_Prec (const rl2 )))0-- | 'readPrec' function for an application of the type constructor-- based on 'readPrec' and 'readListPrec' functions for the argument types.---- @since 4.10.0.0liftReadPrec2 ::ReadPrec a ->ReadPrec [a ]->ReadPrec b ->ReadPrec [b ]->ReadPrec (f a b )liftReadPrec2 rp1 rl1 rp2 rl2 =readS_to_Prec $ liftReadsPrec2 (readPrec_to_S rp1 )(readPrec_to_S rl1 0)(readPrec_to_S rp2 )(readPrec_to_S rl2 0)-- | 'readListPrec' function for an application of the type constructor-- based on 'readPrec' and 'readListPrec' functions for the argument types.---- The default definition uses 'liftReadList2'. Instances that define-- 'liftReadPrec2' should also define 'liftReadListPrec2' as-- 'liftReadListPrec2Default'.---- @since 4.10.0.0liftReadListPrec2 ::ReadPrec a ->ReadPrec [a ]->ReadPrec b ->ReadPrec [b ]->ReadPrec [f a b ]liftReadListPrec2 rp1 rl1 rp2 rl2 =readS_to_Prec $ \_->liftReadList2 (readPrec_to_S rp1 )(readPrec_to_S rl1 0)(readPrec_to_S rp2 )(readPrec_to_S rl2 0)-- | Lift the standard 'readsPrec' function through the type constructor.---- @since 4.9.0.0readsPrec2::(Read2 f ,Read a ,Read b )=>Int->ReadS (f a b )readsPrec2 =liftReadsPrec2 readsPrec readList readsPrec readList -- | Lift the standard 'readPrec' function through the type constructor.---- @since 4.10.0.0readPrec2::(Read2 f ,Read a ,Read b )=>ReadPrec (f a b )readPrec2 =liftReadPrec2 readPrec readListPrec readPrec readListPrec -- | A possible replacement definition for the 'liftReadList2' method.-- This is only needed for 'Read2' instances where 'liftReadListPrec2' isn't-- defined as 'liftReadListPrec2Default'.---- @since 4.10.0.0liftReadList2Default::Read2 f =>(Int->ReadS a )->ReadS [a ]->(Int->ReadS b )->ReadS [b ]->ReadS [f a b ]liftReadList2Default rp1 rl1 rp2 rl2 =readPrec_to_S (liftReadListPrec2 (readS_to_Prec rp1 )(readS_to_Prec (const rl1 ))(readS_to_Prec rp2 )(readS_to_Prec (const rl2 )))0-- | A possible replacement definition for the 'liftReadListPrec2' method,-- defined using 'liftReadPrec2'.---- @since 4.10.0.0liftReadListPrec2Default::Read2 f =>ReadPrec a ->ReadPrec [a ]->ReadPrec b ->ReadPrec [b ]->ReadPrec [f a b ]liftReadListPrec2Default rp1 rl1 rp2 rl2 =list (liftReadPrec2 rp1 rl1 rp2 rl2 )-- | Lifting of the 'Show' class to binary type constructors.---- @since 4.9.0.0classShow2 f where-- | 'showsPrec' function for an application of the type constructor-- based on 'showsPrec' and 'showList' functions for the argument types.---- @since 4.9.0.0liftShowsPrec2 ::(Int->a ->ShowS )->([a ]->ShowS )->(Int->b ->ShowS )->([b ]->ShowS )->Int->f a b ->ShowS -- | 'showList' function for an application of the type constructor-- based on 'showsPrec' and 'showList' functions for the argument types.-- The default implementation using standard list syntax is correct-- for most types.---- @since 4.9.0.0liftShowList2 ::(Int->a ->ShowS )->([a ]->ShowS )->(Int->b ->ShowS )->([b ]->ShowS )->[f a b ]->ShowS liftShowList2 sp1 sl1 sp2 sl2 =showListWith (liftShowsPrec2 sp1 sl1 sp2 sl2 0)-- | Lift the standard 'showsPrec' function through the type constructor.---- @since 4.9.0.0showsPrec2::(Show2 f ,Show a ,Show b )=>Int->f a b ->ShowS showsPrec2 =liftShowsPrec2 showsPrec showList showsPrec showList -- Instances for Prelude type constructors-- | @since 4.9.0.0instanceEq1 Maybe whereliftEq _Nothing Nothing =TrueliftEq_Nothing (Just _)=FalseliftEq_(Just _)Nothing =FalseliftEqeq (Just x )(Just y )=eq x y -- | @since 4.9.0.0instanceOrd1 Maybe whereliftCompare _Nothing Nothing =EQliftCompare_Nothing (Just _)=LTliftCompare_(Just _)Nothing =GTliftComparecomp (Just x )(Just y )=comp x y -- | @since 4.9.0.0instanceRead1 Maybe whereliftReadPrec rp _=parens (expectP (Ident "Nothing")*> pure Nothing )<|> readData (readUnaryWith rp "Just"Just )liftReadListPrec =liftReadListPrecDefault liftReadList =liftReadListDefault -- | @since 4.9.0.0instanceShow1 Maybe whereliftShowsPrec ___Nothing =showString "Nothing"liftShowsPrecsp _d (Just x )=showsUnaryWith sp "Just"d x -- | @since 4.9.0.0instanceEq1 []whereliftEq _[][]=TrueliftEq_[](_:_)=FalseliftEq_(_:_)[]=FalseliftEqeq (x :xs )(y :ys )=eq x y &&liftEq eq xs ys -- | @since 4.9.0.0instanceOrd1 []whereliftCompare _[][]=EQliftCompare_[](_:_)=LTliftCompare_(_:_)[]=GTliftComparecomp (x :xs )(y :ys )=comp x y `mappend `liftCompare comp xs ys -- | @since 4.9.0.0instanceRead1 []whereliftReadPrec _rl =rl liftReadListPrec =liftReadListPrecDefault liftReadList =liftReadListDefault -- | @since 4.9.0.0instanceShow1 []whereliftShowsPrec _sl _=sl -- | @since 4.10.0.0instanceEq1 NonEmpty whereliftEq eq (a :| as)(b :| bs )=eq a b &&liftEq eq asbs -- | @since 4.10.0.0instanceOrd1 NonEmpty whereliftCompare cmp (a :| as)(b :| bs )=cmp a b `mappend `liftCompare cmp asbs -- | @since 4.10.0.0instanceRead1 NonEmpty whereliftReadsPrec rdP rdL p s =readParen (p >5)(\s' ->do(a ,s'' )<-rdP 6s' (":|",s''' )<-lex s'' (as,s'''' )<-rdL s''' return (a :| as,s'''' ))s -- | @since 4.10.0.0instanceShow1 NonEmpty whereliftShowsPrec shwP shwL p (a :| as)=showParen (p >5)$ shwP 6a . showString " :| ". shwL as-- | @since 4.9.0.0instanceEq2 (,)whereliftEq2 e1 e2 (x1 ,y1 )(x2 ,y2 )=e1 x1 x2 &&e2 y1 y2 -- | @since 4.9.0.0instanceOrd2 (,)whereliftCompare2 comp1 comp2 (x1 ,y1 )(x2 ,y2 )=comp1 x1 x2 `mappend `comp2 y1 y2 -- | @since 4.9.0.0instanceRead2 (,)whereliftReadPrec2 rp1 _rp2 _=parens $ paren $ dox <-rp1 expectP (Punc ",")y <-rp2 return (x ,y )liftReadListPrec2 =liftReadListPrec2Default liftReadList2 =liftReadList2Default -- | @since 4.9.0.0instanceShow2 (,)whereliftShowsPrec2 sp1 _sp2 __(x ,y )=showChar '('. sp1 0x . showChar ','. sp2 0y . showChar ')'-- | @since 4.9.0.0instance(Eqa )=>Eq1 ((,)a )whereliftEq =liftEq2 (==)-- | @since 4.9.0.0instance(Orda )=>Ord1 ((,)a )whereliftCompare =liftCompare2 compare-- | @since 4.9.0.0instance(Read a )=>Read1 ((,)a )whereliftReadPrec =liftReadPrec2 readPrec readListPrec liftReadListPrec =liftReadListPrecDefault liftReadList =liftReadListDefault -- | @since 4.9.0.0instance(Show a )=>Show1 ((,)a )whereliftShowsPrec =liftShowsPrec2 showsPrec showList -- | @since 4.9.0.0instanceEq2 Either whereliftEq2 e1 _(Left x )(Left y )=e1 x y liftEq2__(Left _)(Right _)=FalseliftEq2__(Right _)(Left _)=FalseliftEq2_e2 (Right x )(Right y )=e2 x y -- | @since 4.9.0.0instanceOrd2 Either whereliftCompare2 comp1 _(Left x )(Left y )=comp1 x y liftCompare2__(Left _)(Right _)=LTliftCompare2__(Right _)(Left _)=GTliftCompare2_comp2 (Right x )(Right y )=comp2 x y -- | @since 4.9.0.0instanceRead2 Either whereliftReadPrec2 rp1 _rp2 _=readData $ readUnaryWith rp1 "Left"Left <|> readUnaryWith rp2 "Right"Right liftReadListPrec2 =liftReadListPrec2Default liftReadList2 =liftReadList2Default -- | @since 4.9.0.0instanceShow2 Either whereliftShowsPrec2 sp1 ___d (Left x )=showsUnaryWith sp1 "Left"d x liftShowsPrec2__sp2 _d (Right x )=showsUnaryWith sp2 "Right"d x -- | @since 4.9.0.0instance(Eqa )=>Eq1 (Either a )whereliftEq =liftEq2 (==)-- | @since 4.9.0.0instance(Orda )=>Ord1 (Either a )whereliftCompare =liftCompare2 compare-- | @since 4.9.0.0instance(Read a )=>Read1 (Either a )whereliftReadPrec =liftReadPrec2 readPrec readListPrec liftReadListPrec =liftReadListPrecDefault liftReadList =liftReadListDefault -- | @since 4.9.0.0instance(Show a )=>Show1 (Either a )whereliftShowsPrec =liftShowsPrec2 showsPrec showList -- Instances for other functors defined in the base package-- | @since 4.9.0.0instanceEq1 Identity whereliftEq eq (Identity x )(Identity y )=eq x y -- | @since 4.9.0.0instanceOrd1 Identity whereliftCompare comp (Identity x )(Identity y )=comp x y -- | @since 4.9.0.0instanceRead1 Identity whereliftReadPrec rp _=readData $ readUnaryWith rp "Identity"Identity liftReadListPrec =liftReadListPrecDefault liftReadList =liftReadListDefault -- | @since 4.9.0.0instanceShow1 Identity whereliftShowsPrec sp _d (Identity x )=showsUnaryWith sp "Identity"d x -- | @since 4.9.0.0instanceEq2 Const whereliftEq2 eq _(Const x )(Const y )=eq x y -- | @since 4.9.0.0instanceOrd2 Const whereliftCompare2 comp _(Const x )(Const y )=comp x y -- | @since 4.9.0.0instanceRead2 Const whereliftReadPrec2 rp ___=readData $ readUnaryWith rp "Const"Const liftReadListPrec2 =liftReadListPrec2Default liftReadList2 =liftReadList2Default -- | @since 4.9.0.0instanceShow2 Const whereliftShowsPrec2 sp ___d (Const x )=showsUnaryWith sp "Const"d x -- | @since 4.9.0.0instance(Eqa )=>Eq1 (Const a )whereliftEq =liftEq2 (==)-- | @since 4.9.0.0instance(Orda )=>Ord1 (Const a )whereliftCompare =liftCompare2 compare-- | @since 4.9.0.0instance(Read a )=>Read1 (Const a )whereliftReadPrec =liftReadPrec2 readPrec readListPrec liftReadListPrec =liftReadListPrecDefault liftReadList =liftReadListDefault -- | @since 4.9.0.0instance(Show a )=>Show1 (Const a )whereliftShowsPrec =liftShowsPrec2 showsPrec showList -- Proxy unfortunately imports this module, hence these instances are placed-- here,-- | @since 4.9.0.0instanceEq1 Proxy whereliftEq ___=True-- | @since 4.9.0.0instanceOrd1 Proxy whereliftCompare ___=EQ-- | @since 4.9.0.0instanceShow1 Proxy whereliftShowsPrec ____=showString "Proxy"-- | @since 4.9.0.0instanceRead1 Proxy whereliftReadPrec __=parens (expectP (Ident "Proxy")*> pure Proxy )liftReadListPrec =liftReadListPrecDefault liftReadList =liftReadListDefault -- | @since 4.12.0.0instanceEq1 Down whereliftEq eq (Down x )(Down y )=eq x y -- | @since 4.12.0.0instanceOrd1 Down whereliftCompare comp (Down x )(Down y )=comp x y -- | @since 4.12.0.0instanceRead1 Down whereliftReadsPrec rp _=readsData $ readsUnaryWith rp "Down"Down -- | @since 4.12.0.0instanceShow1 Down whereliftShowsPrec sp _d (Down x )=showsUnaryWith sp "Down"d x -- Building blocks-- | @'readsData' p d@ is a parser for datatypes where each alternative-- begins with a data constructor. It parses the constructor and-- passes it to @p@. Parsers for various constructors can be constructed-- with 'readsUnary', 'readsUnary1' and 'readsBinary1', and combined with-- @mappend@ from the @Monoid@ class.---- @since 4.9.0.0readsData::(String ->ReadS a )->Int->ReadS a readsData reader d =readParen (d >10)$ \r ->[res |(kw ,s )<-lex r ,res <-reader kw s ]-- | @'readData' p@ is a parser for datatypes where each alternative-- begins with a data constructor. It parses the constructor and-- passes it to @p@. Parsers for various constructors can be constructed-- with 'readUnaryWith' and 'readBinaryWith', and combined with-- '(<|>)' from the 'Alternative' class.---- @since 4.10.0.0readData::ReadPrec a ->ReadPrec a readData reader =parens $ prec 10reader -- | @'readsUnaryWith' rp n c n'@ matches the name of a unary data constructor-- and then parses its argument using @rp@.---- @since 4.9.0.0readsUnaryWith::(Int->ReadS a )->String ->(a ->t )->String ->ReadS t readsUnaryWith rp name cons kw s =[(cons x ,t )|kw ==name ,(x ,t )<-rp 11s ]-- | @'readUnaryWith' rp n c'@ matches the name of a unary data constructor-- and then parses its argument using @rp@.---- @since 4.10.0.0readUnaryWith::ReadPrec a ->String ->(a ->t )->ReadPrec t readUnaryWith rp name cons =doexpectP $ Ident name x <-step rp return $ cons x -- | @'readsBinaryWith' rp1 rp2 n c n'@ matches the name of a binary-- data constructor and then parses its arguments using @rp1@ and @rp2@-- respectively.---- @since 4.9.0.0readsBinaryWith::(Int->ReadS a )->(Int->ReadS b )->String ->(a ->b ->t )->String ->ReadS t readsBinaryWith rp1 rp2 name cons kw s =[(cons x y ,u )|kw ==name ,(x ,t )<-rp1 11s ,(y ,u )<-rp2 11t ]-- | @'readBinaryWith' rp1 rp2 n c'@ matches the name of a binary-- data constructor and then parses its arguments using @rp1@ and @rp2@-- respectively.---- @since 4.10.0.0readBinaryWith::ReadPrec a ->ReadPrec b ->String ->(a ->b ->t )->ReadPrec t readBinaryWith rp1 rp2 name cons =doexpectP $ Ident name x <-step rp1 y <-step rp2 return $ cons x y -- | @'showsUnaryWith' sp n d x@ produces the string representation of a-- unary data constructor with name @n@ and argument @x@, in precedence-- context @d@.---- @since 4.9.0.0showsUnaryWith::(Int->a ->ShowS )->String ->Int->a ->ShowS showsUnaryWith sp name d x =showParen (d >10)$ showString name . showChar ' '. sp 11x -- | @'showsBinaryWith' sp1 sp2 n d x y@ produces the string-- representation of a binary data constructor with name @n@ and arguments-- @x@ and @y@, in precedence context @d@.---- @since 4.9.0.0showsBinaryWith::(Int->a ->ShowS )->(Int->b ->ShowS )->String ->Int->a ->b ->ShowS showsBinaryWith sp1 sp2 name d x y =showParen (d >10)$ showString name . showChar ' '. sp1 11x . showChar ' '. sp2 11y -- Obsolete building blocks-- | @'readsUnary' n c n'@ matches the name of a unary data constructor-- and then parses its argument using 'readsPrec'.---- @since 4.9.0.0{-# DEPRECATEDreadsUnary"Use readsUnaryWith to define liftReadsPrec"#-}readsUnary::(Read a )=>String ->(a ->t )->String ->ReadS t readsUnary name cons kw s =[(cons x ,t )|kw ==name ,(x ,t )<-readsPrec 11s ]-- | @'readsUnary1' n c n'@ matches the name of a unary data constructor-- and then parses its argument using 'readsPrec1'.---- @since 4.9.0.0{-# DEPRECATEDreadsUnary1"Use readsUnaryWith to define liftReadsPrec"#-}readsUnary1::(Read1 f ,Read a )=>String ->(f a ->t )->String ->ReadS t readsUnary1 name cons kw s =[(cons x ,t )|kw ==name ,(x ,t )<-readsPrec1 11s ]-- | @'readsBinary1' n c n'@ matches the name of a binary data constructor-- and then parses its arguments using 'readsPrec1'.---- @since 4.9.0.0{-# DEPRECATEDreadsBinary1"Use readsBinaryWith to define liftReadsPrec"#-}readsBinary1::(Read1 f ,Read1 g ,Read a )=>String ->(f a ->g a ->t )->String ->ReadS t readsBinary1 name cons kw s =[(cons x y ,u )|kw ==name ,(x ,t )<-readsPrec1 11s ,(y ,u )<-readsPrec1 11t ]-- | @'showsUnary' n d x@ produces the string representation of a unary data-- constructor with name @n@ and argument @x@, in precedence context @d@.---- @since 4.9.0.0{-# DEPRECATEDshowsUnary"Use showsUnaryWith to define liftShowsPrec"#-}showsUnary::(Show a )=>String ->Int->a ->ShowS showsUnary name d x =showParen (d >10)$ showString name . showChar ' '. showsPrec 11x -- | @'showsUnary1' n d x@ produces the string representation of a unary data-- constructor with name @n@ and argument @x@, in precedence context @d@.---- @since 4.9.0.0{-# DEPRECATEDshowsUnary1"Use showsUnaryWith to define liftShowsPrec"#-}showsUnary1::(Show1 f ,Show a )=>String ->Int->f a ->ShowS showsUnary1 name d x =showParen (d >10)$ showString name . showChar ' '. showsPrec1 11x -- | @'showsBinary1' n d x y@ produces the string representation of a binary-- data constructor with name @n@ and arguments @x@ and @y@, in precedence-- context @d@.---- @since 4.9.0.0{-# DEPRECATEDshowsBinary1"Use showsBinaryWith to define liftShowsPrec"#-}showsBinary1::(Show1 f ,Show1 g ,Show a )=>String ->Int->f a ->g a ->ShowS showsBinary1 name d x y =showParen (d >10)$ showString name . showChar ' '. showsPrec1 11x . showChar ' '. showsPrec1 11y {- $example
These functions can be used to assemble 'Read' and 'Show' instances for
new algebraic types. For example, given the definition
> data T f a = Zero a | One (f a) | Two a (f a)
a standard 'Read1' instance may be defined as
> instance (Read1 f) => Read1 (T f) where
> liftReadPrec rp rl = readData $
> readUnaryWith rp "Zero" Zero <|>
> readUnaryWith (liftReadPrec rp rl) "One" One <|>
> readBinaryWith rp (liftReadPrec rp rl) "Two" Two
> liftReadListPrec = liftReadListPrecDefault
and the corresponding 'Show1' instance as
> instance (Show1 f) => Show1 (T f) where
> liftShowsPrec sp _ d (Zero x) =
> showsUnaryWith sp "Zero" d x
> liftShowsPrec sp sl d (One x) =
> showsUnaryWith (liftShowsPrec sp sl) "One" d x
> liftShowsPrec sp sl d (Two x y) =
> showsBinaryWith sp (liftShowsPrec sp sl) "Two" d x y
-}