-- | -- Module : Text.Show.Pragmatic -- Copyright : (c) Justus Sagemüller 2017 -- License : GPL v3 -- -- Maintainer : (@) jsagemue $ uni-koeln.de -- Stability : experimental -- Portability : portable -- {-# LANGUAGE CPP #-} module Text.Show.Pragmatic where import Prelude hiding (Show(..), shows) import qualified Prelude import Data.Int (Int8, Int16, Int32, Int64) import Data.Word (Word8, Word16, Word32, Word64) import Data.Ratio #if MIN_VERSION_base(4,8,0) import Numeric.Natural (Natural) #endif #if MIN_VERSION_base(4,10,0) import Type.Reflection (TyCon, SomeTypeRep, Module) #endif #if MIN_VERSION_base(4,9,0) import GHC.Stack (SrcLoc, CallStack) #endif #if MIN_VERSION_base(3,0,0) import Control.Exception.Base ( SomeException, ArithException, ErrorCall, IOException , MaskingState , ArrayException, AsyncException #if MIN_VERSION_base(4,7,0) , SomeAsyncException #endif , AssertionFailed #if MIN_VERSION_base(4,10,0) , CompactionFailed #endif #if MIN_VERSION_base(4,7,1) , AllocationLimitExceeded #endif , Deadlock, BlockedIndefinitelyOnSTM , BlockedIndefinitelyOnMVar , NestedAtomically, NonTermination #if MIN_VERSION_base(4,9,0) , TypeError #endif , NoMethodError , RecUpdError, RecConError, RecSelError, PatternMatchFail ) #endif import Data.Char (GeneralCategory) import Text.Read.Lex (Number, Lexeme) #if MIN_VERSION_base(4,7,0) import GHC.Fingerprint.Type (Fingerprint) #endif import System.IO (IOMode) import System.IO.Error (IOErrorType) import System.Exit (ExitCode) import Foreign.Ptr (IntPtr, WordPtr) import Foreign.C.Types ( CUIntMax, CIntMax, CUIntPtr, CIntPtr , CSUSeconds, CUSeconds, CTime, CClock , CSigAtomic, CWchar, CSize, CPtrdiff , CDouble, CFloat #if MIN_VERSION_base(4,10,0) , CBool #endif , CULLong, CLLong, CULong, CLong, CUInt, CInt, CUShort, CShort , CUChar, CSChar, CChar ) #if MIN_VERSION_base(4,10,0) import GHC.TypeNats (SomeNat) import GHC.TypeLits (SomeSymbol) #endif #if MIN_VERSION_base(4,9,0) import GHC.Generics ( DecidedStrictness, SourceStrictness, SourceUnpackedness , Associativity, Fixity ) #endif import Data.Monoid (Any, All) #if MIN_VERSION_base(4,4,0) import GHC.IO.Encoding.Types (CodingProgress, TextEncoding) import GHC.IO.Encoding.Failure (CodingFailureMode) #endif import GHC.IO.Device (SeekMode) import GHC.IO.Handle (NewlineMode, Newline, BufferMode, Handle, HandlePosn) #if MIN_VERSION_base(4,10,0) import GHC.IO.Handle.Lock (FileLockingNotSupported) #endif #if MIN_VERSION_base(4,9,0) import GHC.StaticPtr (StaticPtrInfo) #endif import System.Posix.Types ( Fd #if MIN_VERSION_base(4,10,0) , CTimer, CKey, CId, CFsFilCnt, CFsBlkCnt, CClockId , CBlkCnt, CBlkSize #endif , CRLim, CTcflag, CSpeed, CCc, CUid , CNlink, CGid, CSsize, CPid, COff, CMode, CIno, CDev ) #if MIN_VERSION_base(4,8,1) import GHC.Event (Lifetime, Event, FdKey) #endif #if MIN_VERSION_base(2,1,0) import Data.Dynamic (Dynamic) #endif import GHC.Conc (ThreadStatus, BlockReason) import Control.Concurrent (ThreadId) #if MIN_VERSION_base(4,8,0) import Data.Version (Version) #endif #if MIN_VERSION_base(4,5,0) import Data.Version (Version) #endif #if MIN_VERSION_base(4,10,0) import GHC.Stats (RTSStats) #endif #if MIN_VERSION_base(4,9,0) import GHC.RTS.Flags ( RTSFlags #if MIN_VERSION_base(4,10,0) , ParFlags #endif , TickyFlags, TraceFlags, DoTrace, ProfFlags , DoHeapProfile, CCFlags, DoCostCentres, DebugFlags, MiscFlags , ConcFlags, GCFlags, GiveGCStats ) #endif import Data.Data ( Fixity, ConstrRep, DataRep #if MIN_VERSION_base(4,0,0) , Constr #endif , DataType ) #if MIN_VERSION_base(4,8,0) import Data.Void #endif -- | A drop-in replacement for 'Prelude.Show'. The behaviour is mostly the same: -- the result of 'show' should be valid Haskell code, and 'read'ing back such a -- value should give the original value – but, unlike in 'Prelude.Show', we don't -- require this in an /exact/ sense, i.e. @'read' ('show' x) == x@ is not necessarily -- fulfilled. -- -- Notably for floating-point values, we allow a slight deviation if -- it considerably shortens the shown representation: for example, -- @0.90000004 :: Float@, which can easily come up as -- the result of a computation which should in principle be exactly @0.9@, is shown -- as @0.9@ instead. We do however /not/ commit to any particular fixed precision; -- it depends on the type and the order of magnitude which amount of rounding is -- appropriate. See for some examples. class Show a where {-# MINIMAL showsPrec | show #-} showsPrec :: Int -> a -> ShowS showsPrec _ x = (show x++) show :: a -> String show = (`shows`"") showList :: [a] -> ShowS showList [] = ("[]"++) showList (x:xs) = ('[':) . shows x . flip (foldr (\y -> (',':) . shows y)) xs . (']':) shows :: Show a => a -> ShowS shows = showsPrec 0 #define StdShow(A) \ instance Show (A) where { \ show = Prelude.show; \ showsPrec = Prelude.showsPrec; \ showList = Prelude.showList } StdShow (Bool) StdShow (Int) StdShow (Int8) StdShow (Int16) StdShow (Int32) StdShow (Int64) StdShow (Integer) #if MIN_VERSION_base(4,8,0) StdShow (Natural) #endif StdShow (Ordering) StdShow (Word) StdShow (Word8) StdShow (Word16) StdShow (Word32) StdShow (Word64) #if MIN_VERSION_base(4,9,0) StdShow (CallStack) #endif #if MIN_VERSION_base(4,10,0) StdShow (SomeTypeRep) #endif StdShow (()) #if MIN_VERSION_base(4,10,0) StdShow (TyCon) StdShow (Module) #endif #if MIN_VERSION_base(4,9,0) StdShow (SrcLoc) #endif #if MIN_VERSION_base(3,0,0) StdShow (SomeException) #endif StdShow (GeneralCategory) StdShow (Number) StdShow (Lexeme) #if MIN_VERSION_base(4,7,0) StdShow (Fingerprint) #endif StdShow (IOMode) StdShow (IntPtr) StdShow (WordPtr) StdShow (CUIntMax) StdShow (CIntMax) StdShow (CUIntPtr) StdShow (CIntPtr) StdShow (CSUSeconds) StdShow (CUSeconds) StdShow (CTime) StdShow (CClock) StdShow (CSigAtomic) StdShow (CWchar) StdShow (CSize) StdShow (CPtrdiff) #if MIN_VERSION_base(4,10,0) StdShow (CBool) #endif StdShow (CULLong) StdShow (CLLong) StdShow (CULong) StdShow (CLong) StdShow (CUInt) StdShow (CInt) StdShow (CUShort) StdShow (CShort) StdShow (CUChar) StdShow (CSChar) StdShow (CChar) #if MIN_VERSION_base(4,10,0) StdShow (SomeNat) StdShow (SomeSymbol) #endif #if MIN_VERSION_base(4,9,0) StdShow (DecidedStrictness) StdShow (SourceStrictness) StdShow (SourceUnpackedness) StdShow (Associativity) StdShow (GHC.Generics.Fixity) #endif StdShow (Any) StdShow (All) #if MIN_VERSION_base(4,0,0) StdShow (ArithException) StdShow (ErrorCall) #endif #if MIN_VERSION_base(4,1,0) StdShow (IOException) #endif StdShow (MaskingState) #if MIN_VERSION_base(4,4,0) StdShow (CodingProgress) #endif #if MIN_VERSION_base(4,3,0) StdShow (TextEncoding) #endif StdShow (SeekMode) StdShow (NewlineMode) StdShow (Newline) StdShow (BufferMode) #if MIN_VERSION_base(4,1,0) StdShow (Handle) StdShow (IOErrorType) #endif StdShow (ExitCode) #if MIN_VERSION_base(4,1,0) StdShow (ArrayException) StdShow (AsyncException) #endif #if MIN_VERSION_base(4,7,0) StdShow (SomeAsyncException) #endif #if MIN_VERSION_base(4,1,0) StdShow (AssertionFailed) #endif #if MIN_VERSION_base(4,10,0) StdShow (CompactionFailed) #endif #if MIN_VERSION_base(4,7,1) StdShow (AllocationLimitExceeded) #endif #if MIN_VERSION_base(4,1,0) StdShow (Deadlock) StdShow (BlockedIndefinitelyOnSTM) StdShow (BlockedIndefinitelyOnMVar) StdShow (CodingFailureMode) #endif StdShow (Fd) #if MIN_VERSION_base(4,10,0) StdShow (CTimer) StdShow (CKey) StdShow (CId) StdShow (CFsFilCnt) StdShow (CFsBlkCnt) StdShow (CClockId) StdShow (CBlkCnt) StdShow (CBlkSize) #endif StdShow (CRLim) StdShow (CTcflag) StdShow (CSpeed) StdShow (CCc) StdShow (CUid) StdShow (CNlink) StdShow (CGid) StdShow (CSsize) StdShow (CPid) StdShow (COff) StdShow (CMode) StdShow (CIno) StdShow (CDev) #if MIN_VERSION_base(4,8,1) StdShow (Lifetime) StdShow (Event) #endif #if MIN_VERSION_base(2,1,0) StdShow (Dynamic) #endif StdShow (ThreadStatus) StdShow (BlockReason) #if MIN_VERSION_base(4,2,0) StdShow (ThreadId) #endif #if MIN_VERSION_base(4,0,0) StdShow (NestedAtomically) StdShow (NonTermination) #endif #if MIN_VERSION_base(4,9,0) StdShow (TypeError) #endif #if MIN_VERSION_base(4,0,0) StdShow (NoMethodError) StdShow (RecUpdError) StdShow (RecConError) StdShow (RecSelError) StdShow (PatternMatchFail) #endif StdShow (FdKey) #if MIN_VERSION_base(4,10,0) StdShow (FileLockingNotSupported) #endif #if MIN_VERSION_base(4,1,0) StdShow (HandlePosn) #endif #if MIN_VERSION_base(4,8,0) StdShow (Version) #endif #if MIN_VERSION_base(4,10,0) StdShow (RTSStats) StdShow (ParFlags) #endif #if MIN_VERSION_base(4,9,0) StdShow (RTSFlags) StdShow (TickyFlags) StdShow (TraceFlags) StdShow (DoTrace) StdShow (ProfFlags) StdShow (DoHeapProfile) StdShow (CCFlags) StdShow (DoCostCentres) StdShow (DebugFlags) StdShow (MiscFlags) StdShow (ConcFlags) StdShow (GCFlags) StdShow (GiveGCStats) #endif StdShow (Data.Data.Fixity) StdShow (ConstrRep) StdShow (DataRep) #if MIN_VERSION_base(4,0,0) StdShow (Constr) #endif StdShow (DataType) #if MIN_VERSION_base(4,9,0) StdShow (StaticPtrInfo) #endif #if MIN_VERSION_base(4,8,0) StdShow (Void) #endif instance Show Char where show c | c>'\31', c/='\'', c/='\\' = '\'':c:"'" | otherwise = Prelude.show c showList cs = ('"':) . flip (foldr showc) cs . ('"':) where showc '"' = ("\\\""++) showc '\\' = ("\\\\"++) showc '\SO' = ("\\SO\\&"++) -- prevent problem with "\SO\&H"≈[14,72] getting -- shown as "\SOH"≈[2]. (Thanks, QuickCheck!) showc c | c>'\31' = (c:) | otherwise = case show c of ('\'':q) -> case break (=='\'') q of (r,"'") -> (r++) instance Show Float where showsPrec = ltdPrecShowsPrec 7 instance Show Double where showsPrec = ltdPrecShowsPrec 10 instance Show CFloat where showsPrec = ltdPrecShowsPrec 5 instance Show CDouble where showsPrec = ltdPrecShowsPrec 10 -- | @'ltdPrecShowsPrec' prcn@ displays floating-point values with a precision -- of at least @prcn@ digits. That does not mean it will necessarily display -- that many digits, rather it tries to always choose the shortest representation -- with the required precision. ltdPrecShowsPrec :: (RealFloat n) => Int -> Int -> n -> ShowS ltdPrecShowsPrec _ _ 0 = ("0"++) ltdPrecShowsPrec precision p n | not (n==n) = ("NaN"++) | n<0 = showParen (p>5) $ ('-':) . ltdPrecShowsPrec precision 0 (negate n) | n==n*2 = ("Infinity"++) | e₁₀<7 && lrDigs <= e₁₀ = (rDigits++) . (replicate (e₁₀-lrDigs) '0' ++) | e₁₀>0 && e₁₀<3 = (take e₁₀ rDigits++) . ('.':) . (drop e₁₀ rDigits++) | e₁₀> -2 && e₁₀<=0 = ("0."++) . (replicate (negate e₁₀) '0'++) . (rDigits++) | [hd] <- rDigits = (hd:) . ("e"++) . shows (e₁₀-1) | (hd:qd@(_:_)) <- rDigits = (hd:) . ('.':) . (qd++) . ("e"++) . shows (e₁₀-1) where (e₁₀,m₁₀Approx) = correctPrecision . ceiling $ logBase 10 n where correctPrecision e = case show (round $ n * 10^^(precision+2 - e) :: Int) of digits | length digits <= precision+2 -> (e,digits) | otherwise -> correctPrecision $ e+1 (rApprZeroes, rDigits') = break (>'0') . reverse $ m₁₀Approx rDigits = reverse rDigits' lrDigs = length rDigits instance (Show a) => Show [a] where showsPrec _ = showList instance (Show a, Show b) => Show (a,b) where showsPrec _ (a,b) = ('(':) . shows a . (',':) . shows b . (')':) instance (Show a, Show b, Show c) => Show (a,b,c) where showsPrec _ (a,b,c) = ('(':) . shows a . (',':) . shows b . (',':) . shows c . (')':) instance (Show a, Show b, Show c, Show d) => Show (a,b,c,d) where showsPrec _ (a,b,c,d) = ('(':) . shows a . (',':) . shows b . (',':) . shows c . (',':) . shows d . (')':) instance (Integral i, Show i) => Show (Ratio i) where showsPrec p n | n<0 = showParen (p>5) $ ('-':) . showsPrec 6 (-n) | denominator n == 1 = shows $ numerator n | otherwise = showParen (p>6) $ shows (numerator n) . ('/':) . shows (denominator n) -- | Drop-in for the standard screen-displaying function. This is useful as a GHCi -- evaluation action; invoke with -- @ -- $ ghci -interactive-print=Text.Show.Pragmatic.print -- @ -- to get more concise output from the REPL. print :: Show a => a -> IO () print = putStrLn . show