{-# LANGUAGE BangPatterns #-} {-# LANGUAGE CPP #-} {-# LANGUAGE DeriveDataTypeable #-} {-# LANGUAGE DeriveGeneric #-} {-# LANGUAGE EmptyDataDecls #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE MagicHash #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE OverloadedStrings #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE StandaloneDeriving #-} {-# LANGUAGE TypeOperators #-} {-# LANGUAGE TemplateHaskell #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeSynonymInstances #-} #if __GLASGOW_HASKELL__ >= 706 {-# LANGUAGE DataKinds #-} {-# LANGUAGE PolyKinds #-} #endif #if __GLASGOW_HASKELL__ >= 800 {-# LANGUAGE DeriveLift #-} #endif {-| Module: TextShow.Generic Copyright: (C) 2014-2017 Ryan Scott License: BSD-style (see the file LICENSE) Maintainer: Ryan Scott Stability: Provisional Portability: GHC Generic versions of 'TextShow' and 'TextShow1' class functions, as an alternative to "TextShow.TH", which uses Template Haskell. Because there is no 'Generic2' class, 'TextShow2' cannot be implemented generically. This implementation is loosely based off of the @Generics.Deriving.Show@ module from the @generic-deriving@ library. /Since: 2/ -} module TextShow.Generic ( -- * Generic @show@ functions -- $generics -- ** Understanding a compiler error -- $generic_err genericShowt , genericShowtl , genericShowtPrec , genericShowtlPrec , genericShowtList , genericShowtlList , genericShowb , genericShowbPrec , genericShowbList , genericPrintT , genericPrintTL , genericHPrintT , genericHPrintTL , genericLiftShowbPrec , genericShowbPrec1 -- * Internals -- ** 'Builder' , GTextShowB(..) , GTextShowConB(..) , ShowFunsB(..) -- ** Strict 'TS.Text' , GTextShowT(..) , GTextShowConT(..) , ShowFunsT(..) -- ** Lazy 'TL.Text' , GTextShowTL(..) , GTextShowConTL(..) , ShowFunsTL(..) -- ** Other internals , IsNullary(..) , ConType(..) , Zero , One ) where import Data.Data (Data, Typeable) import Data.Functor.Contravariant (Contravariant(..)) import Data.Monoid.Compat ((<>)) import qualified Data.Text as TS (Text, pack, singleton) import qualified Data.Text.IO as TS (putStrLn, hPutStrLn) import qualified Data.Text.Lazy as TL (Text, pack, singleton) import qualified Data.Text.Lazy.IO as TL (putStrLn, hPutStrLn) import qualified Data.Text.Lazy.Builder as TB (fromString, singleton) import Data.Text.Lazy.Builder (Builder) import Generics.Deriving.Base import GHC.Exts (Char(C#), Double(D#), Float(F#), Int(I#), Word(W#)) import GHC.Show (appPrec, appPrec1) import Language.Haskell.TH.Lift import Prelude () import Prelude.Compat import System.IO (Handle) import TextShow.Classes (TextShow(..), TextShow1(..), showbListWith, showbParen, showbSpace, showtListWith, showtParen, showtSpace, showtlListWith, showtlParen, showtlSpace, liftShowtPrec, liftShowtlPrec) import TextShow.Instances () import TextShow.TH.Internal (deriveTextShow) import TextShow.Utils (isInfixDataCon, isSymVar, isTupleString) {- $generics 'TextShow' instances can be easily defined for data types that are 'Generic' instances. The easiest way to do this is to use the @DeriveGeneric@ extension. @ {-# LANGUAGE DeriveGeneric #-} import GHC.Generics import TextShow import TextShow.Generic data D a = D a deriving (Generic, Generic1) instance TextShow a => TextShow (D a) where showbPrec = 'genericShowbPrec' instance TextShow1 D where liftShowbPrec = 'genericLiftShowbPrec' @ -} {- $generic_err Suppose you intend to use 'genericShowbPrec' to define a 'TextShow' instance. @ data Oops = Oops -- forgot to add \"deriving Generic\" here! instance TextShow Oops where showbPrec = 'genericShowbPrec' @ If you forget to add a @deriving 'Generic'@ clause to your data type, at compile-time, you might get an error message that begins roughly as follows: @ No instance for ('GTextShowB' 'Zero' (Rep Oops)) @ This error can be confusing, but don't let it intimidate you. The correct fix is simply to add the missing \"@deriving 'Generic'@\" clause. Similarly, if the compiler complains about not having an instance for @('GTextShowB' 'One' (Rep1 Oops1))@, add a \"@deriving 'Generic1'@\" clause. -} -- | A 'Generic' implementation of 'showt'. -- -- /Since: 2/ genericShowt :: (Generic a, GTextShowT Zero (Rep a)) => a -> TS.Text genericShowt = genericShowtPrec 0 -- | A 'Generic' implementation of 'showtl'. -- -- /Since: 2/ genericShowtl :: (Generic a, GTextShowTL Zero (Rep a)) => a -> TL.Text genericShowtl = genericShowtlPrec 0 -- | A 'Generic' implementation of 'showPrect'. -- -- /Since: 2/ genericShowtPrec :: (Generic a, GTextShowT Zero (Rep a)) => Int -> a -> TS.Text genericShowtPrec p = gShowtPrec NoShowFunsT p . from -- | A 'Generic' implementation of 'showtlPrec'. -- -- /Since: 2/ genericShowtlPrec :: (Generic a, GTextShowTL Zero (Rep a)) => Int -> a -> TL.Text genericShowtlPrec p = gShowtlPrec NoShowFunsTL p . from -- | A 'Generic' implementation of 'showtList'. -- -- /Since: 2/ genericShowtList :: (Generic a, GTextShowT Zero (Rep a)) => [a] -> TS.Text genericShowtList = showtListWith genericShowt -- | A 'Generic' implementation of 'showtlList'. -- -- /Since: 2/ genericShowtlList :: (Generic a, GTextShowTL Zero (Rep a)) => [a] -> TL.Text genericShowtlList = showtlListWith genericShowtl -- | A 'Generic' implementation of 'showb'. -- -- /Since: 2/ genericShowb :: (Generic a, GTextShowB Zero (Rep a)) => a -> Builder genericShowb = genericShowbPrec 0 -- | A 'Generic' implementation of 'showbPrec'. -- -- /Since: 2/ genericShowbPrec :: (Generic a, GTextShowB Zero (Rep a)) => Int -> a -> Builder genericShowbPrec p = gShowbPrec NoShowFunsB p . from -- | A 'Generic' implementation of 'showbList'. -- -- /Since: 2/ genericShowbList :: (Generic a, GTextShowB Zero (Rep a)) => [a] -> Builder genericShowbList = showbListWith genericShowb -- | A 'Generic' implementation of 'printT'. -- -- /Since: 2/ genericPrintT :: (Generic a, GTextShowT Zero (Rep a)) => a -> IO () genericPrintT = TS.putStrLn . genericShowt -- | A 'Generic' implementation of 'printTL'. -- -- /Since: 2/ genericPrintTL :: (Generic a, GTextShowTL Zero (Rep a)) => a -> IO () genericPrintTL = TL.putStrLn . genericShowtl -- | A 'Generic' implementation of 'hPrintT'. -- -- /Since: 2/ genericHPrintT :: (Generic a, GTextShowT Zero (Rep a)) => Handle -> a -> IO () genericHPrintT h = TS.hPutStrLn h . genericShowt -- | A 'Generic' implementation of 'hPrintTL'. -- -- /Since: 2/ genericHPrintTL :: (Generic a, GTextShowTL Zero (Rep a)) => Handle -> a -> IO () genericHPrintTL h = TL.hPutStrLn h . genericShowtl -- | A 'Generic1' implementation of 'genericLiftShowbPrec'. -- -- /Since: 2/ genericLiftShowbPrec :: (Generic1 f, GTextShowB One (Rep1 f)) => (Int -> a -> Builder) -> ([a] -> Builder) -> Int -> f a -> Builder genericLiftShowbPrec sp sl p = gShowbPrec (Show1FunsB sp sl) p . from1 -- | A 'Generic'/'Generic1' implementation of 'showbPrec1'. -- -- /Since: 2/ genericShowbPrec1 :: ( Generic a, Generic1 f , GTextShowB Zero (Rep a) , GTextShowB One (Rep1 f) ) => Int -> f a -> Builder genericShowbPrec1 = genericLiftShowbPrec genericShowbPrec genericShowbList ------------------------------------------------------------------------------- -- | Whether a constructor is a record ('Rec'), a tuple ('Tup'), is prefix ('Pref'), -- or infix ('Inf'). -- -- /Since: 2/ data ConType = Rec | Tup | Pref | Inf String deriving ( Data , Eq , Generic , Ord , Read , Show , Typeable #if __GLASGOW_HASKELL__ >= 800 , Lift #endif ) -- | A type-level indicator that 'TextShow' is being derived generically. -- -- /Since: 3.2/ data Zero -- | A type-level indicator that 'TextShow1' is being derived generically. -- -- /Since: 3.2/ data One {- I'm not particularly proud of the code below. The issue is that we need to be able to generically work over Builders, strict Text, and lazy Text. We could just work generically over Builders only and then convert to Text after the fact, but that results in a drastic slowdown for certain datatypes (see GH-21 for an example). For the most part, the shared functionality could be abstracted with a subclass of Monoid that supports fromString, fromChar, etc. But there's a very small chance that the code below is ever going to inline properly, and the runtime cost of all those dictinary lookups is likely to be as bad as converting to Text at the end, if not worse. Therefore, I perform some ugly CPP hackery to copy-paste the generic functionality three times, once for each Text/Builder variant. I suppose I could use TH instead to make this look a little nicer, but I haven't attempted that. -} #if __GLASGOW_HASKELL__ >= 708 #define DERIVE_TYPEABLE(name) deriving instance Typeable name #else #define DERIVE_TYPEABLE(name) #endif #if __GLASGOW_HASKELL__ >= 711 #define HASH_FUNS(text_type,one_hash,two_hash,hash_prec,from_char,from_string) \ one_hash, two_hash :: text_type; \ hash_prec :: Int -> Int; \ one_hash = from_char '#'; \ two_hash = from_string "##"; \ hash_prec = const 0 #else #define HASH_FUNS(text_type,one_hash,two_hash,hash_prec,from_char,from_string) \ one_hash, two_hash :: text_type; \ hash_prec :: Int -> Int; \ one_hash = mempty; \ two_hash = mempty; \ hash_prec = id #endif #define GTEXT_SHOW(text_type,show_funs,no_show_funs,show1_funs,one_hash,two_hash,hash_prec,gtext_show,gshow_prec,gtext_show_con,gshow_prec_con,show_prec,lift_show_prec,show_space,show_paren,show_list_with,from_char,from_string) \ {- | A 'show_funs' value either stores nothing (for 'TextShow') or it stores \ the two function arguments that show occurrences of the type parameter (for \ 'TextShow1'). \ \ /Since: 3.4/ \ -}; \ data show_funs arity a where { \ no_show_funs :: show_funs Zero a \ ; show1_funs :: (Int -> a -> text_type) -> ([a] -> text_type) -> show_funs One a \ } deriving Typeable; \ \ instance Contravariant (show_funs arity) where { \ contramap _ no_show_funs = no_show_funs \ ; contramap f (show1_funs sp sl) = show1_funs (\p -> sp p . f) (sl . map f) \ }; \ \ {- | Class of generic representation types that can be converted to \ a 'text_type'. The @arity@ type variable indicates which type class is \ used. @'gtext_show' 'Zero'@ indicates 'TextShow' behavior, and \ @'gtext_show' 'One'@ indicates 'TextShow1' behavior. \ \ /Since: 3.4/ \ -}; \ class gtext_show arity f where { \ {- | This is used as the default generic implementation of 'show_prec' (if the \ @arity@ is 'Zero') or 'lift_show_prec' (if the @arity@ is 'One'). \ -} \ ; gshow_prec :: show_funs arity a -> Int -> f a -> text_type \ }; \ \ DERIVE_TYPEABLE(gtext_show); \ \ instance gtext_show arity f => gtext_show arity (D1 d f) where { \ gshow_prec sfs p (M1 x) = gshow_prec sfs p x \ }; \ \ instance gtext_show Zero V1 where { \ gshow_prec _ _ !_ = error "Void show_prec" \ }; \ \ instance gtext_show One V1 where { \ gshow_prec _ _ !_ = error "Void lift_show_prec" \ }; \ \ instance (gtext_show arity f, gtext_show arity g) => gtext_show arity (f :+: g) where { \ gshow_prec sfs p (L1 x) = gshow_prec sfs p x \ ; gshow_prec sfs p (R1 x) = gshow_prec sfs p x \ }; \ \ instance (Constructor c, gtext_show_con arity f, IsNullary f) \ => gtext_show arity (C1 c f) where { \ gshow_prec sfs p c@(M1 x) = case fixity of { \ Prefix -> show_paren ( p > appPrec \ && not (isNullary x || conIsTuple c) \ ) $ \ (if conIsTuple c \ then mempty \ else let cn = conName c \ in show_paren (isInfixDataCon cn) $ from_string cn) \ <> (if isNullary x || conIsTuple c \ then mempty \ else from_char ' ') \ <> showbBraces t (gshow_prec_con t sfs appPrec1 x) \ ; Infix _ m -> show_paren (p > m) $ gshow_prec_con t sfs (m+1) x \ } \ where { \ fixity :: Fixity \ ; fixity = conFixity c \ \ ; t :: ConType \ ; t = if conIsRecord c \ then Rec \ else case conIsTuple c of { \ True -> Tup \ ; False -> case fixity of { \ Prefix -> Pref \ ; Infix _ _ -> Inf $ conName c \ }; \ } \ \ ; showbBraces :: ConType -> text_type -> text_type \ ; showbBraces Rec b = from_char '{' <> b <> from_char '}' \ ; showbBraces Tup b = from_char '(' <> b <> from_char ')' \ ; showbBraces Pref b = b \ ; showbBraces (Inf _) b = b \ \ ; conIsTuple :: C1 c f p -> Bool \ ; conIsTuple = isTupleString . conName \ }; \ }; \ \ {- | Class of generic representation types for which the 'ConType' has been \ determined. The @arity@ type variable indicates which type class is \ used. @'gtext_show_con' 'Zero'@ indicates 'TextShow' behavior, and \ @'gtext_show_con' 'One'@ indicates 'TextShow1' behavior. \ -}; \ class gtext_show_con arity f where { \ {- | Convert value of a specific 'ConType' to a 'text_type' with the given \ precedence. \ -} \ ; gshow_prec_con :: ConType -> show_funs arity a -> Int -> f a -> text_type \ }; \ \ DERIVE_TYPEABLE(gtext_show_con); \ \ instance gtext_show_con arity U1 where { \ gshow_prec_con _ _ _ U1 = mempty \ }; \ \ instance gtext_show_con One Par1 where { \ gshow_prec_con _ (show1_funs sp _) p (Par1 x) = sp p x \ }; \ \ instance TextShow c => gtext_show_con arity (K1 i c) where { \ gshow_prec_con _ _ p (K1 x) = show_prec p x \ }; \ \ instance TextShow1 f => gtext_show_con One (Rec1 f) where { \ gshow_prec_con _ (show1_funs sp sl) p (Rec1 x) = lift_show_prec sp sl p x \ }; \ \ instance (Selector s, gtext_show_con arity f) => gtext_show_con arity (S1 s f) where { \ gshow_prec_con t sfs p sel@(M1 x) \ | selName sel == "" = gshow_prec_con t sfs p x \ | otherwise = infixRec \ <> " = " \ <> gshow_prec_con t sfs 0 x \ where { \ infixRec :: text_type \ ; infixRec | isSymVar selectorName \ = from_char '(' <> from_string selectorName <> from_char ')' \ | otherwise \ = from_string selectorName \ \ ; selectorName :: String \ ; selectorName = selName sel \ } \ }; \ \ instance (gtext_show_con arity f, gtext_show_con arity g) \ => gtext_show_con arity (f :*: g) where { \ gshow_prec_con t@Rec sfs _ (a :*: b) = \ gshow_prec_con t sfs 0 a \ <> ", " \ <> gshow_prec_con t sfs 0 b \ ; gshow_prec_con t@(Inf o) sfs p (a :*: b) = \ gshow_prec_con t sfs p a \ <> show_space \ <> infixOp \ <> show_space \ <> gshow_prec_con t sfs p b \ where { \ infixOp :: text_type \ ; infixOp = if isInfixDataCon o \ then from_string o \ else from_char '`' <> from_string o <> from_char '`' \ } \ ; gshow_prec_con t@Tup sfs _ (a :*: b) = \ gshow_prec_con t sfs 0 a \ <> from_char ',' \ <> gshow_prec_con t sfs 0 b \ ; gshow_prec_con t@Pref sfs p (a :*: b) = \ gshow_prec_con t sfs p a \ <> show_space \ <> gshow_prec_con t sfs p b \ }; \ \ instance (TextShow1 f, gtext_show_con One g) => gtext_show_con One (f :.: g) where { \ gshow_prec_con t sfs p (Comp1 x) = \ let gspc = gshow_prec_con t sfs \ in lift_show_prec gspc (show_list_with (gspc 0)) p x \ }; \ \ instance gtext_show_con arity UChar where { \ gshow_prec_con _ _ p (UChar c) = show_prec (hash_prec p) (C# c) <> one_hash \ }; \ \ instance gtext_show_con arity UDouble where { \ gshow_prec_con _ _ p (UDouble d) = show_prec (hash_prec p) (D# d) <> two_hash \ }; \ \ instance gtext_show_con arity UFloat where { \ gshow_prec_con _ _ p (UFloat f) = show_prec (hash_prec p) (F# f) <> one_hash \ }; \ \ instance gtext_show_con arity UInt where { \ gshow_prec_con _ _ p (UInt i) = show_prec (hash_prec p) (I# i) <> one_hash \ }; \ \ instance gtext_show_con arity UWord where { \ gshow_prec_con _ _ p (UWord w) = show_prec (hash_prec p) (W# w) <> two_hash \ }; \ \ HASH_FUNS(text_type,one_hash,two_hash,hash_prec,from_char,from_string); GTEXT_SHOW(Builder,ShowFunsB,NoShowFunsB,Show1FunsB,oneHashB,twoHashB,hashPrecB,GTextShowB,gShowbPrec,GTextShowConB,gShowbPrecCon,showbPrec,liftShowbPrec,showbSpace,showbParen,showbListWith,TB.singleton,TB.fromString) GTEXT_SHOW(TS.Text,ShowFunsT,NoShowFunsT,Show1FunsT,oneHashT,twoHashT,hashPrecT,GTextShowT,gShowtPrec,GTextShowConT,gShowtPrecCon,showtPrec,liftShowtPrec,showtSpace,showtParen,showtListWith,TS.singleton,TS.pack) GTEXT_SHOW(TL.Text,ShowFunsTL,NoShowFunsTL,Show1FunsTL,oneHashTL,twoHashTL,hashPrecTL,GTextShowTL,gShowtlPrec,GTextShowConTL,gShowtlPrecCon,showtlPrec,liftShowtlPrec,showtlSpace,showtlParen,showtlListWith,TL.singleton,TL.pack) -- | Class of generic representation types that represent a constructor with -- zero or more fields. class IsNullary f where -- Returns 'True' if the constructor has no fields. isNullary :: f a -> Bool instance IsNullary U1 where isNullary _ = True instance IsNullary Par1 where isNullary _ = False instance IsNullary (K1 i c) where isNullary _ = False instance IsNullary f => IsNullary (S1 s f) where isNullary (M1 x) = isNullary x instance IsNullary (Rec1 f) where isNullary _ = False instance IsNullary (f :*: g) where isNullary _ = False instance IsNullary (f :.: g) where isNullary _ = False instance IsNullary UChar where isNullary _ = False instance IsNullary UDouble where isNullary _ = False instance IsNullary UFloat where isNullary _ = False instance IsNullary UInt where isNullary _ = False instance IsNullary UWord where isNullary _ = False ------------------------------------------------------------------------------- $(deriveTextShow ''ConType) #if __GLASGOW_HASKELL__ < 800 $(deriveLift ''ConType) #endif