{-# LANGUAGE Trustworthy #-} {-# LANGUAGE CPP, NoImplicitPrelude, BangPatterns, StandaloneDeriving, MagicHash, UnboxedTuples #-} {-# OPTIONS_HADDOCK hide #-} #include "MachDeps.h" #if SIZEOF_HSWORD == 4 #define DIGITS 9 #define BASE 1000000000 #elif SIZEOF_HSWORD == 8 #define DIGITS 18 #define BASE 1000000000000000000 #else #error Please define DIGITS and BASE -- DIGITS should be the largest integer such that -- 10^DIGITS < 2^(SIZEOF_HSWORD * 8 - 1) -- BASE should be 10^DIGITS. Note that ^ is not available yet. #endif ----------------------------------------------------------------------------- -- | -- Module : GHC.Show -- Copyright : (c) The University of Glasgow, 1992-2002 -- License : see libraries/base/LICENSE -- -- Maintainer : cvs-ghc@haskell.org -- Stability : internal -- Portability : non-portable (GHC Extensions) -- -- The 'Show' class, and related operations. -- ----------------------------------------------------------------------------- module GHC.Show ( Show(..), ShowS, -- Instances for Show: (), [], Bool, Ordering, Int, Char -- Show support code shows, showChar, showString, showMultiLineString, showParen, showList__, showCommaSpace, showSpace, showLitChar, showLitString, protectEsc, intToDigit, showSignedInt, appPrec, appPrec1, -- Character operations asciiTab, ) where import GHC.Base import GHC.List ((!!), foldr1, break) import GHC.Num import GHC.Stack.Types -- | The @shows@ functions return a function that prepends the -- output 'String' to an existing 'String'. This allows constant-time -- concatenation of results using function composition. type ShowS = String -> String -- | Conversion of values to readable 'String's. -- -- 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)\"@. class Show a where {-# MINIMAL showsPrec | show #-} -- | 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 'Text.Read.Read' and 'Show' satisfy the following: -- -- * @(x,\"\")@ is an element of -- @('Text.Read.readsPrec' d ('showsPrec' d x \"\"))@. -- -- That is, 'Text.Read.readsPrec' parses the string produced by -- 'showsPrec', and delivers the value that 'showsPrec' started with. 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 -- | A specialised variant of 'showsPrec', using precedence context -- zero, and returning an ordinary 'String'. show :: a -> String -- | The method 'showList' is provided to allow the programmer to -- give a specialised way of showing lists of values. -- For example, this is used by the predefined 'Show' instance of -- the 'Char' type, where values of type 'String' should be shown -- in double quotes, rather than between square brackets. showList :: [a] -> ShowS showsPrec _ x s = show x ++ s show x = shows x "" showList ls s = showList__ shows ls s showList__ :: (a -> ShowS) -> [a] -> ShowS showList__ _ [] s = "[]" ++ s showList__ showx (x:xs) s = '[' : showx x (showl xs) where showl [] = ']' : s showl (y:ys) = ',' : showx y (showl ys) appPrec, appPrec1 :: Int -- Use unboxed stuff because we don't have overloaded numerics yet appPrec = I# 10# -- Precedence of application: -- one more than the maximum operator precedence of 9 appPrec1 = I# 11# -- appPrec + 1 -------------------------------------------------------------- -- Simple Instances -------------------------------------------------------------- deriving instance Show () -- | @since 2.01 instance Show a => Show [a] where {-# SPECIALISE instance Show [String] #-} {-# SPECIALISE instance Show [Char] #-} {-# SPECIALISE instance Show [Int] #-} showsPrec _ = showList deriving instance Show Bool deriving instance Show Ordering -- | @since 2.01 instance Show Char where showsPrec _ '\'' = showString "'\\''" showsPrec _ c = showChar '\'' . showLitChar c . showChar '\'' showList cs = showChar '"' . showLitString cs . showChar '"' -- | @since 2.01 instance Show Int where showsPrec = showSignedInt -- | @since 2.01 instance Show Word where showsPrec _ (W# w) = showWord w showWord :: Word# -> ShowS showWord w# cs | isTrue# (w# `ltWord#` 10##) = C# (chr# (ord# '0'# +# word2Int# w#)) : cs | otherwise = case chr# (ord# '0'# +# word2Int# (w# `remWord#` 10##)) of c# -> showWord (w# `quotWord#` 10##) (C# c# : cs) deriving instance Show a => Show (Maybe a) deriving instance Show a => Show (NonEmpty a) -- | @since 2.01 instance Show TyCon where showsPrec p (TyCon _ _ _ tc_name _ _) = showsPrec p tc_name -- | @since 4.9.0.0 instance Show TrName where showsPrec _ (TrNameS s) = showString (unpackCString# s) showsPrec _ (TrNameD s) = showString s -- | @since 4.9.0.0 instance Show Module where showsPrec _ (Module p m) = shows p . (':' :) . shows m -- | @since 4.9.0.0 instance Show CallStack where showsPrec _ = shows . getCallStack deriving instance Show SrcLoc -------------------------------------------------------------- -- Show instances for the first few tuple -------------------------------------------------------------- -- The explicit 's' parameters are important -- Otherwise GHC thinks that "shows x" might take a lot of work to compute -- and generates defns like -- showsPrec _ (x,y) = let sx = shows x; sy = shows y in -- \s -> showChar '(' (sx (showChar ',' (sy (showChar ')' s)))) -- | @since 2.01 instance (Show a, Show b) => Show (a,b) where showsPrec _ (a,b) s = show_tuple [shows a, shows b] s -- | @since 2.01 instance (Show a, Show b, Show c) => Show (a, b, c) where showsPrec _ (a,b,c) s = show_tuple [shows a, shows b, shows c] s -- | @since 2.01 instance (Show a, Show b, Show c, Show d) => Show (a, b, c, d) where showsPrec _ (a,b,c,d) s = show_tuple [shows a, shows b, shows c, shows d] s -- | @since 2.01 instance (Show a, Show b, Show c, Show d, Show e) => Show (a, b, c, d, e) where showsPrec _ (a,b,c,d,e) s = show_tuple [shows a, shows b, shows c, shows d, shows e] s -- | @since 2.01 instance (Show a, Show b, Show c, Show d, Show e, Show f) => Show (a,b,c,d,e,f) where showsPrec _ (a,b,c,d,e,f) s = show_tuple [shows a, shows b, shows c, shows d, shows e, shows f] s -- | @since 2.01 instance (Show a, Show b, Show c, Show d, Show e, Show f, Show g) => Show (a,b,c,d,e,f,g) where showsPrec _ (a,b,c,d,e,f,g) s = show_tuple [shows a, shows b, shows c, shows d, shows e, shows f, shows g] s -- | @since 2.01 instance (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) where showsPrec _ (a,b,c,d,e,f,g,h) s = show_tuple [shows a, shows b, shows c, shows d, shows e, shows f, shows g, shows h] s -- | @since 2.01 instance (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) where showsPrec _ (a,b,c,d,e,f,g,h,i) s = show_tuple [shows a, shows b, shows c, shows d, shows e, shows f, shows g, shows h, shows i] s -- | @since 2.01 instance (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) where showsPrec _ (a,b,c,d,e,f,g,h,i,j) s = show_tuple [shows a, shows b, shows c, shows d, shows e, shows f, shows g, shows h, shows i, shows j] s -- | @since 2.01 instance (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) where showsPrec _ (a,b,c,d,e,f,g,h,i,j,k) s = show_tuple [shows a, shows b, shows c, shows d, shows e, shows f, shows g, shows h, shows i, shows j, shows k] s -- | @since 2.01 instance (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) where showsPrec _ (a,b,c,d,e,f,g,h,i,j,k,l) s = show_tuple [shows a, shows b, shows c, shows d, shows e, shows f, shows g, shows h, shows i, shows j, shows k, shows l] s -- | @since 2.01 instance (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) where showsPrec _ (a,b,c,d,e,f,g,h,i,j,k,l,m) s = show_tuple [shows a, shows b, shows c, shows d, shows e, shows f, shows g, shows h, shows i, shows j, shows k, shows l, shows m] s -- | @since 2.01 instance (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) where showsPrec _ (a,b,c,d,e,f,g,h,i,j,k,l,m,n) s = show_tuple [shows a, shows b, shows c, shows d, shows e, shows f, shows g, shows h, shows i, shows j, shows k, shows l, shows m, shows n] s -- | @since 2.01 instance (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) where showsPrec _ (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o) s = show_tuple [shows a, shows b, shows c, shows d, shows e, shows f, shows g, shows h, shows i, shows j, shows k, shows l, shows m, shows n, shows o] s show_tuple :: [ShowS] -> ShowS show_tuple ss = showChar '(' . foldr1 (\s r -> s . showChar ',' . r) ss . showChar ')' -------------------------------------------------------------- -- Support code for Show -------------------------------------------------------------- -- | equivalent to 'showsPrec' with a precedence of 0. shows :: (Show a) => a -> ShowS shows = showsPrec 0 -- | utility function converting a 'Char' to a show function that -- simply prepends the character unchanged. showChar :: Char -> ShowS showChar = (:) -- | utility function converting a 'String' to a show function that -- simply prepends the string unchanged. showString :: String -> ShowS showString = (++) -- | utility function that surrounds the inner show function with -- parentheses when the 'Bool' parameter is 'True'. showParen :: Bool -> ShowS -> ShowS showParen b p = if b then showChar '(' . p . showChar ')' else p showSpace :: ShowS showSpace = {-showChar ' '-} \ xs -> ' ' : xs showCommaSpace :: ShowS showCommaSpace = showString ", " -- Code specific for characters -- | Convert a character to a string using only printable characters, -- using Haskell source-language escape conventions. For example: -- -- > showLitChar '\n' s = "\\n" ++ s -- showLitChar :: Char -> ShowS showLitChar c s | c > '\DEL' = showChar '\\' (protectEsc isDec (shows (ord c)) s) showLitChar '\DEL' s = showString "\\DEL" s showLitChar '\\' s = showString "\\\\" s showLitChar c s | c >= ' ' = showChar c s showLitChar '\a' s = showString "\\a" s showLitChar '\b' s = showString "\\b" s showLitChar '\f' s = showString "\\f" s showLitChar '\n' s = showString "\\n" s showLitChar '\r' s = showString "\\r" s showLitChar '\t' s = showString "\\t" s showLitChar '\v' s = showString "\\v" s showLitChar '\SO' s = protectEsc (== 'H') (showString "\\SO") s showLitChar c s = showString ('\\' : asciiTab!!ord c) s -- I've done manual eta-expansion here, because otherwise it's -- impossible to stop (asciiTab!!ord) getting floated out as an MFE showLitString :: String -> ShowS -- | 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 showLitString [] s = s showLitString ('"' : cs) s = showString "\\\"" (showLitString cs s) showLitString (c : cs) s = showLitChar c (showLitString cs s) -- Making 's' an explicit parameter makes it clear to GHC that -- showLitString has arity 2, which avoids it allocating an extra lambda -- The sticking point is the recursive call to (showLitString cs), which -- it can't figure out would be ok with arity 2. showMultiLineString :: String -> [String] -- | 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 "hello\ngoodbye\nblah"@ -- returns @["\"hello\\n\\", "\\goodbye\n\\", "\\blah\""]@ showMultiLineString str = go '\"' str where go ch s = case break (== '\n') s of (l, _:s'@(_:_)) -> (ch : showLitString l "\\n\\") : go '\\' s' (l, "\n") -> [ch : showLitString l "\\n\""] (l, _) -> [ch : showLitString l "\""] isDec :: Char -> Bool isDec c = c >= '0' && c <= '9' protectEsc :: (Char -> Bool) -> ShowS -> ShowS protectEsc p f = f . cont where cont s@(c:_) | p c = "\\&" ++ s cont s = s asciiTab :: [String] asciiTab = -- Using an array drags in the array module. listArray ('\NUL', ' ') ["NUL", "SOH", "STX", "ETX", "EOT", "ENQ", "ACK", "BEL", "BS", "HT", "LF", "VT", "FF", "CR", "SO", "SI", "DLE", "DC1", "DC2", "DC3", "DC4", "NAK", "SYN", "ETB", "CAN", "EM", "SUB", "ESC", "FS", "GS", "RS", "US", "SP"] -- Code specific for Ints. -- | Convert an 'Int' in the range @0@..@15@ to the corresponding single -- digit 'Char'. This function fails on other inputs, and generates -- lower-case hexadecimal digits. intToDigit :: Int -> Char intToDigit (I# i) | isTrue# (i >=# 0#) && isTrue# (i <=# 9#) = unsafeChr (ord '0' + I# i) | isTrue# (i >=# 10#) && isTrue# (i <=# 15#) = unsafeChr (ord 'a' + I# i - 10) | otherwise = errorWithoutStackTrace ("Char.intToDigit: not a digit " ++ show (I# i)) showSignedInt :: Int -> Int -> ShowS showSignedInt (I# p) (I# n) r | isTrue# (n <# 0#) && isTrue# (p ># 6#) = '(' : itos n (')' : r) | otherwise = itos n r itos :: Int# -> String -> String itos n# cs | isTrue# (n# <# 0#) = let !(I# minInt#) = minInt in if isTrue# (n# ==# minInt#) -- negateInt# minInt overflows, so we can't do that: then '-' : (case n# `quotRemInt#` 10# of (# q, r #) -> itos' (negateInt# q) (itos' (negateInt# r) cs)) else '-' : itos' (negateInt# n#) cs | otherwise = itos' n# cs where itos' :: Int# -> String -> String itos' x# cs' | isTrue# (x# <# 10#) = C# (chr# (ord# '0'# +# x#)) : cs' | otherwise = case x# `quotRemInt#` 10# of (# q, r #) -> case chr# (ord# '0'# +# r) of c# -> itos' q (C# c# : cs') -------------------------------------------------------------- -- The Integer instances for Show -------------------------------------------------------------- -- | @since 2.01 instance Show Integer where showsPrec p n r | p > 6 && n < 0 = '(' : integerToString n (')' : r) -- Minor point: testing p first gives better code -- in the not-uncommon case where the p argument -- is a constant | otherwise = integerToString n r showList = showList__ (showsPrec 0) -- Divide an conquer implementation of string conversion integerToString :: Integer -> String -> String integerToString n0 cs0 | n0 < 0 = '-' : integerToString' (- n0) cs0 | otherwise = integerToString' n0 cs0 where integerToString' :: Integer -> String -> String integerToString' n cs | n < BASE = jhead (fromInteger n) cs | otherwise = jprinth (jsplitf (BASE*BASE) n) cs -- Split n into digits in base p. We first split n into digits -- in base p*p and then split each of these digits into two. -- Note that the first 'digit' modulo p*p may have a leading zero -- in base p that we need to drop - this is what jsplith takes care of. -- jsplitb the handles the remaining digits. jsplitf :: Integer -> Integer -> [Integer] jsplitf p n | p > n = [n] | otherwise = jsplith p (jsplitf (p*p) n) jsplith :: Integer -> [Integer] -> [Integer] jsplith p (n:ns) = case n `quotRemInteger` p of (# q, r #) -> if q > 0 then q : r : jsplitb p ns else r : jsplitb p ns jsplith _ [] = errorWithoutStackTrace "jsplith: []" jsplitb :: Integer -> [Integer] -> [Integer] jsplitb _ [] = [] jsplitb p (n:ns) = case n `quotRemInteger` p of (# q, r #) -> q : r : jsplitb p ns -- Convert a number that has been split into digits in base BASE^2 -- this includes a last splitting step and then conversion of digits -- that all fit into a machine word. jprinth :: [Integer] -> String -> String jprinth (n:ns) cs = case n `quotRemInteger` BASE of (# q', r' #) -> let q = fromInteger q' r = fromInteger r' in if q > 0 then jhead q $ jblock r $ jprintb ns cs else jhead r $ jprintb ns cs jprinth [] _ = errorWithoutStackTrace "jprinth []" jprintb :: [Integer] -> String -> String jprintb [] cs = cs jprintb (n:ns) cs = case n `quotRemInteger` BASE of (# q', r' #) -> let q = fromInteger q' r = fromInteger r' in jblock q $ jblock r $ jprintb ns cs -- Convert an integer that fits into a machine word. Again, we have two -- functions, one that drops leading zeros (jhead) and one that doesn't -- (jblock) jhead :: Int -> String -> String jhead n cs | n < 10 = case unsafeChr (ord '0' + n) of c@(C# _) -> c : cs | otherwise = case unsafeChr (ord '0' + r) of c@(C# _) -> jhead q (c : cs) where (q, r) = n `quotRemInt` 10 jblock = jblock' {- ' -} DIGITS jblock' :: Int -> Int -> String -> String jblock' d n cs | d == 1 = case unsafeChr (ord '0' + n) of c@(C# _) -> c : cs | otherwise = case unsafeChr (ord '0' + r) of c@(C# _) -> jblock' (d - 1) q (c : cs) where (q, r) = n `quotRemInt` 10