{-# LANGUAGE Safe #-} {-# LANGUAGE GADTs #-} {-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-} ----------------------------------------------------------------------------- -- | -- Module : Text.Printf -- Copyright : (c) Lennart Augustsson and Bart Massey 2013 -- License : BSD-style (see the file LICENSE in this distribution) -- -- Maintainer : Bart Massey -- Stability : provisional -- Portability : portable -- -- A C @printf(3)@-like formatter. This version has been -- extended by Bart Massey as per the recommendations of -- John Meacham and Simon Marlow -- -- to support extensible formatting for new datatypes. It -- has also been extended to support almost all C -- @printf(3)@ syntax. ----------------------------------------------------------------------------- module Text.Printf( -- * Printing Functions printf, hPrintf, -- * Extending To New Types -- -- | This 'printf' can be extended to format types -- other than those provided for by default. This -- is done by instantiating 'PrintfArg' and providing -- a 'formatArg' for the type. It is possible to -- provide a 'parseFormat' to process type-specific -- modifiers, but the default instance is usually -- the best choice. -- -- For example: -- -- > instance PrintfArg () where -- > formatArg x fmt | fmtChar (vFmt 'U' fmt) == 'U' = -- > formatString "()" (fmt { fmtChar = 's', fmtPrecision = Nothing }) -- > formatArg _ fmt = errorBadFormat $ fmtChar fmt -- > -- > main :: IO () -- > main = printf "[%-3.1U]\n" () -- -- prints \"@[() ]@\". Note the use of 'formatString' to -- take care of field formatting specifications in a convenient -- way. PrintfArg(..), FieldFormatter, FieldFormat(..), FormatAdjustment(..), FormatSign(..), vFmt, -- ** Handling Type-specific Modifiers -- -- | In the unlikely case that modifier characters of -- some kind are desirable for a user-provided type, -- a 'ModifierParser' can be provided to process these -- characters. The resulting modifiers will appear in -- the 'FieldFormat' for use by the type-specific formatter. ModifierParser, FormatParse(..), -- ** Standard Formatters -- -- | These formatters for standard types are provided for -- convenience in writting new type-specific formatters: -- a common pattern is to throw to 'formatString' or -- 'formatInteger' to do most of the format handling for -- a new type. formatString, formatChar, formatInt, formatInteger, formatRealFloat, -- ** Raising Errors -- -- | These functions are used internally to raise various -- errors, and are exported for use by new type-specific -- formatters. errorBadFormat, errorShortFormat, errorMissingArgument, errorBadArgument, perror, -- * Implementation Internals -- | These types are needed for implementing processing -- variable numbers of arguments to 'printf' and 'hPrintf'. -- Their implementation is intentionally not visible from -- this module. If you attempt to pass an argument of a type -- which is not an instance of the appropriate class to -- 'printf' or 'hPrintf', then the compiler will report it -- as a missing instance of 'PrintfArg'. (All 'PrintfArg' -- instances are 'PrintfType' instances.) PrintfType, HPrintfType, -- | This class is needed as a Haskell98 compatibility -- workaround for the lack of FlexibleInstances. IsChar(..) ) where import Data.Char import Data.Int import Data.List (stripPrefix) import Data.Word import Numeric import Numeric.Natural import System.IO -- $setup -- >>> import Prelude ------------------- -- | Format a variable number of arguments with the C-style formatting string. -- -- >>> printf "%s, %d, %.4f" "hello" 123 pi -- hello, 123, 3.1416 -- -- The return value is either 'String' or @('IO' a)@ (which -- should be @('IO' ())@, but Haskell's type system -- makes this hard). -- -- The format string consists of ordinary characters and -- /conversion specifications/, which specify how to format -- one of the arguments to 'printf' in the output string. A -- format specification is introduced by the @%@ character; -- this character can be self-escaped into the format string -- using @%%@. A format specification ends with a -- /format character/ that provides the primary information about -- how to format the value. The rest of the conversion -- specification is optional. In order, one may have flag -- characters, a width specifier, a precision specifier, and -- type-specific modifier characters. -- -- Unlike C @printf(3)@, the formatting of this 'printf' -- is driven by the argument type; formatting is type specific. The -- types formatted by 'printf' \"out of the box\" are: -- -- * 'Integral' types, including 'Char' -- -- * 'String' -- -- * 'RealFloat' types -- -- 'printf' is also extensible to support other types: see below. -- -- A conversion specification begins with the -- character @%@, followed by zero or more of the following flags: -- -- > - left adjust (default is right adjust) -- > + always use a sign (+ or -) for signed conversions -- > space leading space for positive numbers in signed conversions -- > 0 pad with zeros rather than spaces -- > # use an \"alternate form\": see below -- -- When both flags are given, @-@ overrides @0@ and @+@ overrides space. -- A negative width specifier in a @*@ conversion is treated as -- positive but implies the left adjust flag. -- -- The \"alternate form\" for unsigned radix conversions is -- as in C @printf(3)@: -- -- > %o prefix with a leading 0 if needed -- > %x prefix with a leading 0x if nonzero -- > %X prefix with a leading 0X if nonzero -- > %b prefix with a leading 0b if nonzero -- > %[eEfFgG] ensure that the number contains a decimal point -- -- Any flags are followed optionally by a field width: -- -- > num field width -- > * as num, but taken from argument list -- -- The field width is a minimum, not a maximum: it will be -- expanded as needed to avoid mutilating a value. -- -- Any field width is followed optionally by a precision: -- -- > .num precision -- > . same as .0 -- > .* as num, but taken from argument list -- -- Negative precision is taken as 0. The meaning of the -- precision depends on the conversion type. -- -- > Integral minimum number of digits to show -- > RealFloat number of digits after the decimal point -- > String maximum number of characters -- -- The precision for Integral types is accomplished by zero-padding. -- If both precision and zero-pad are given for an Integral field, -- the zero-pad is ignored. -- -- Any precision is followed optionally for Integral types -- by a width modifier; the only use of this modifier being -- to set the implicit size of the operand for conversion of -- a negative operand to unsigned: -- -- > hh Int8 -- > h Int16 -- > l Int32 -- > ll Int64 -- > L Int64 -- -- The specification ends with a format character: -- -- > c character Integral -- > d decimal Integral -- > o octal Integral -- > x hexadecimal Integral -- > X hexadecimal Integral -- > b binary Integral -- > u unsigned decimal Integral -- > f floating point RealFloat -- > F floating point RealFloat -- > g general format float RealFloat -- > G general format float RealFloat -- > e exponent format float RealFloat -- > E exponent format float RealFloat -- > s string String -- > v default format any type -- -- The \"%v\" specifier is provided for all built-in types, -- and should be provided for user-defined type formatters -- as well. It picks a \"best\" representation for the given -- type. For the built-in types the \"%v\" specifier is -- converted as follows: -- -- > c Char -- > u other unsigned Integral -- > d other signed Integral -- > g RealFloat -- > s String -- -- Mismatch between the argument types and the format -- string, as well as any other syntactic or semantic errors -- in the format string, will cause an exception to be -- thrown at runtime. -- -- Note that the formatting for 'RealFloat' types is -- currently a bit different from that of C @printf(3)@, -- conforming instead to 'Numeric.showEFloat', -- 'Numeric.showFFloat' and 'Numeric.showGFloat' (and their -- alternate versions 'Numeric.showFFloatAlt' and -- 'Numeric.showGFloatAlt'). This is hard to fix: the fixed -- versions would format in a backward-incompatible way. -- In any case the Haskell behavior is generally more -- sensible than the C behavior. A brief summary of some -- key differences: -- -- * Haskell 'printf' never uses the default \"6-digit\" precision -- used by C printf. -- -- * Haskell 'printf' treats the \"precision\" specifier as -- indicating the number of digits after the decimal point. -- -- * Haskell 'printf' prints the exponent of e-format -- numbers without a gratuitous plus sign, and with the -- minimum possible number of digits. -- -- * Haskell 'printf' will place a zero after a decimal point when -- possible. printf :: (PrintfType r) => String -> r printf fmts = spr fmts [] -- | Similar to 'printf', except that output is via the specified -- 'Handle'. The return type is restricted to @('IO' a)@. hPrintf :: (HPrintfType r) => Handle -> String -> r hPrintf hdl fmts = hspr hdl fmts [] -- |The 'PrintfType' class provides the variable argument magic for -- 'printf'. Its implementation is intentionally not visible from -- this module. If you attempt to pass an argument of a type which -- is not an instance of this class to 'printf' or 'hPrintf', then -- the compiler will report it as a missing instance of 'PrintfArg'. class PrintfType t where spr :: String -> [UPrintf] -> t -- | The 'HPrintfType' class provides the variable argument magic for -- 'hPrintf'. Its implementation is intentionally not visible from -- this module. class HPrintfType t where hspr :: Handle -> String -> [UPrintf] -> t {- not allowed in Haskell 2010 instance PrintfType String where spr fmt args = uprintf fmt (reverse args) -} -- | @since 2.01 instance (IsChar c) => PrintfType [c] where spr fmts args = map fromChar (uprintf fmts (reverse args)) -- Note that this should really be (IO ()), but GHC's -- type system won't readily let us say that without -- bringing the GADTs. So we go conditional for these defs. -- | @since 4.7.0.0 instance (a ~ ()) => PrintfType (IO a) where spr fmts args = putStr $ map fromChar $ uprintf fmts $ reverse args -- | @since 4.7.0.0 instance (a ~ ()) => HPrintfType (IO a) where hspr hdl fmts args = hPutStr hdl (uprintf fmts (reverse args)) -- | @since 2.01 instance (PrintfArg a, PrintfType r) => PrintfType (a -> r) where spr fmts args = \ a -> spr fmts ((parseFormat a, formatArg a) : args) -- | @since 2.01 instance (PrintfArg a, HPrintfType r) => HPrintfType (a -> r) where hspr hdl fmts args = \ a -> hspr hdl fmts ((parseFormat a, formatArg a) : args) -- | Typeclass of 'printf'-formattable values. The 'formatArg' method -- takes a value and a field format descriptor and either fails due -- to a bad descriptor or produces a 'ShowS' as the result. The -- default 'parseFormat' expects no modifiers: this is the normal -- case. Minimal instance: 'formatArg'. class PrintfArg a where -- | @since 4.7.0.0 formatArg :: a -> FieldFormatter -- | @since 4.7.0.0 parseFormat :: a -> ModifierParser parseFormat _ (c : cs) = FormatParse "" c cs parseFormat _ "" = errorShortFormat -- | @since 2.01 instance PrintfArg Char where formatArg = formatChar parseFormat _ cf = parseIntFormat (undefined :: Int) cf -- | @since 2.01 instance (IsChar c) => PrintfArg [c] where formatArg = formatString -- | @since 2.01 instance PrintfArg Int where formatArg = formatInt parseFormat = parseIntFormat -- | @since 2.01 instance PrintfArg Int8 where formatArg = formatInt parseFormat = parseIntFormat -- | @since 2.01 instance PrintfArg Int16 where formatArg = formatInt parseFormat = parseIntFormat -- | @since 2.01 instance PrintfArg Int32 where formatArg = formatInt parseFormat = parseIntFormat -- | @since 2.01 instance PrintfArg Int64 where formatArg = formatInt parseFormat = parseIntFormat -- | @since 2.01 instance PrintfArg Word where formatArg = formatInt parseFormat = parseIntFormat -- | @since 2.01 instance PrintfArg Word8 where formatArg = formatInt parseFormat = parseIntFormat -- | @since 2.01 instance PrintfArg Word16 where formatArg = formatInt parseFormat = parseIntFormat -- | @since 2.01 instance PrintfArg Word32 where formatArg = formatInt parseFormat = parseIntFormat -- | @since 2.01 instance PrintfArg Word64 where formatArg = formatInt parseFormat = parseIntFormat -- | @since 2.01 instance PrintfArg Integer where formatArg = formatInteger parseFormat = parseIntFormat -- | @since 4.8.0.0 instance PrintfArg Natural where formatArg = formatInteger . toInteger parseFormat = parseIntFormat -- | @since 2.01 instance PrintfArg Float where formatArg = formatRealFloat -- | @since 2.01 instance PrintfArg Double where formatArg = formatRealFloat -- | This class, with only the one instance, is used as -- a workaround for the fact that 'String', as a concrete -- type, is not allowable as a typeclass instance. 'IsChar' -- is exported for backward-compatibility. class IsChar c where -- | @since 4.7.0.0 toChar :: c -> Char -- | @since 4.7.0.0 fromChar :: Char -> c -- | @since 2.01 instance IsChar Char where toChar c = c fromChar c = c ------------------- -- | Whether to left-adjust or zero-pad a field. These are -- mutually exclusive, with 'LeftAdjust' taking precedence. -- -- @since 4.7.0.0 data FormatAdjustment = LeftAdjust | ZeroPad -- | How to handle the sign of a numeric field. These are -- mutually exclusive, with 'SignPlus' taking precedence. -- -- @since 4.7.0.0 data FormatSign = SignPlus | SignSpace -- | Description of field formatting for 'formatArg'. See UNIX @printf(3)@ -- for a description of how field formatting works. -- -- @since 4.7.0.0 data FieldFormat = FieldFormat { fmtWidth :: Maybe Int, -- ^ Total width of the field. fmtPrecision :: Maybe Int, -- ^ Secondary field width specifier. fmtAdjust :: Maybe FormatAdjustment, -- ^ Kind of filling or padding -- to be done. fmtSign :: Maybe FormatSign, -- ^ Whether to insist on a -- plus sign for positive -- numbers. fmtAlternate :: Bool, -- ^ Indicates an "alternate -- format". See @printf(3)@ -- for the details, which -- vary by argument spec. fmtModifiers :: String, -- ^ Characters that appeared -- immediately to the left of -- 'fmtChar' in the format -- and were accepted by the -- type's 'parseFormat'. -- Normally the empty string. fmtChar :: Char -- ^ The format character -- 'printf' was invoked -- with. 'formatArg' should -- fail unless this character -- matches the type. It is -- normal to handle many -- different format -- characters for a single -- type. } -- | The \"format parser\" walks over argument-type-specific -- modifier characters to find the primary format character. -- This is the type of its result. -- -- @since 4.7.0.0 data FormatParse = FormatParse { fpModifiers :: String, -- ^ Any modifiers found. fpChar :: Char, -- ^ Primary format character. fpRest :: String -- ^ Rest of the format string. } -- Contains the "modifier letters" that can precede an -- integer type. intModifierMap :: [(String, Integer)] intModifierMap = [ ("hh", toInteger (minBound :: Int8)), ("h", toInteger (minBound :: Int16)), ("l", toInteger (minBound :: Int32)), ("ll", toInteger (minBound :: Int64)), ("L", toInteger (minBound :: Int64)) ] parseIntFormat :: a -> String -> FormatParse parseIntFormat _ s = case foldr matchPrefix Nothing intModifierMap of Just m -> m Nothing -> case s of c : cs -> FormatParse "" c cs "" -> errorShortFormat where matchPrefix (p, _) m@(Just (FormatParse p0 _ _)) | length p0 >= length p = m | otherwise = case getFormat p of Nothing -> m Just fp -> Just fp matchPrefix (p, _) Nothing = getFormat p getFormat p = stripPrefix p s >>= fp where fp (c : cs) = Just $ FormatParse p c cs fp "" = errorShortFormat -- | This is the type of a field formatter reified over its -- argument. -- -- @since 4.7.0.0 type FieldFormatter = FieldFormat -> ShowS -- | Type of a function that will parse modifier characters -- from the format string. -- -- @since 4.7.0.0 type ModifierParser = String -> FormatParse -- | Substitute a \'v\' format character with the given -- default format character in the 'FieldFormat'. A -- convenience for user-implemented types, which should -- support \"%v\". -- -- @since 4.7.0.0 vFmt :: Char -> FieldFormat -> FieldFormat vFmt c ufmt@(FieldFormat {fmtChar = 'v'}) = ufmt {fmtChar = c} vFmt _ ufmt = ufmt -- | Formatter for 'Char' values. -- -- @since 4.7.0.0 formatChar :: Char -> FieldFormatter formatChar x ufmt = formatIntegral (Just 0) (toInteger $ ord x) $ vFmt 'c' ufmt -- | Formatter for 'String' values. -- -- @since 4.7.0.0 formatString :: IsChar a => [a] -> FieldFormatter formatString x ufmt = case fmtChar $ vFmt 's' ufmt of 's' -> map toChar . (adjust ufmt ("", ts) ++) where ts = map toChar $ trunc $ fmtPrecision ufmt where trunc Nothing = x trunc (Just n) = take n x c -> errorBadFormat c -- Possibly apply the int modifiers to get a new -- int width for conversion. fixupMods :: FieldFormat -> Maybe Integer -> Maybe Integer fixupMods ufmt m = let mods = fmtModifiers ufmt in case mods of "" -> m _ -> case lookup mods intModifierMap of Just m0 -> Just m0 Nothing -> perror "unknown format modifier" -- | Formatter for 'Int' values. -- -- @since 4.7.0.0 formatInt :: (Integral a, Bounded a) => a -> FieldFormatter formatInt x ufmt = let lb = toInteger $ minBound `asTypeOf` x m = fixupMods ufmt (Just lb) ufmt' = case lb of 0 -> vFmt 'u' ufmt _ -> ufmt in formatIntegral m (toInteger x) ufmt' -- | Formatter for 'Integer' values. -- -- @since 4.7.0.0 formatInteger :: Integer -> FieldFormatter formatInteger x ufmt = let m = fixupMods ufmt Nothing in formatIntegral m x ufmt -- All formatting for integral types is handled -- consistently. The only difference is between Integer and -- bounded types; this difference is handled by the 'm' -- argument containing the lower bound. formatIntegral :: Maybe Integer -> Integer -> FieldFormatter formatIntegral m x ufmt0 = let prec = fmtPrecision ufmt0 in case fmtChar ufmt of 'd' -> (adjustSigned ufmt (fmti prec x) ++) 'i' -> (adjustSigned ufmt (fmti prec x) ++) 'x' -> (adjust ufmt (fmtu 16 (alt "0x" x) prec m x) ++) 'X' -> (adjust ufmt (upcase $ fmtu 16 (alt "0X" x) prec m x) ++) 'b' -> (adjust ufmt (fmtu 2 (alt "0b" x) prec m x) ++) 'o' -> (adjust ufmt (fmtu 8 (alt "0" x) prec m x) ++) 'u' -> (adjust ufmt (fmtu 10 Nothing prec m x) ++) 'c' | x >= fromIntegral (ord (minBound :: Char)) && x <= fromIntegral (ord (maxBound :: Char)) && fmtPrecision ufmt == Nothing && fmtModifiers ufmt == "" -> formatString [chr $ fromIntegral x] (ufmt { fmtChar = 's' }) 'c' -> perror "illegal char conversion" c -> errorBadFormat c where ufmt = vFmt 'd' $ case ufmt0 of FieldFormat { fmtPrecision = Just _, fmtAdjust = Just ZeroPad } -> ufmt0 { fmtAdjust = Nothing } _ -> ufmt0 alt _ 0 = Nothing alt p _ = case fmtAlternate ufmt of True -> Just p False -> Nothing upcase (s1, s2) = (s1, map toUpper s2) -- | Formatter for 'RealFloat' values. -- -- @since 4.7.0.0 formatRealFloat :: RealFloat a => a -> FieldFormatter formatRealFloat x ufmt = let c = fmtChar $ vFmt 'g' ufmt prec = fmtPrecision ufmt alt = fmtAlternate ufmt in case c of 'e' -> (adjustSigned ufmt (dfmt c prec alt x) ++) 'E' -> (adjustSigned ufmt (dfmt c prec alt x) ++) 'f' -> (adjustSigned ufmt (dfmt c prec alt x) ++) 'F' -> (adjustSigned ufmt (dfmt c prec alt x) ++) 'g' -> (adjustSigned ufmt (dfmt c prec alt x) ++) 'G' -> (adjustSigned ufmt (dfmt c prec alt x) ++) _ -> errorBadFormat c -- This is the type carried around for arguments in -- the varargs code. type UPrintf = (ModifierParser, FieldFormatter) -- Given a format string and a list of formatting functions -- (the actual argument value having already been baked into -- each of these functions before delivery), return the -- actual formatted text string. uprintf :: String -> [UPrintf] -> String uprintf s us = uprintfs s us "" -- This function does the actual work, producing a ShowS -- instead of a string, for future expansion and for -- misguided efficiency. uprintfs :: String -> [UPrintf] -> ShowS uprintfs "" [] = id uprintfs "" (_:_) = errorShortFormat uprintfs ('%':'%':cs) us = ('%' :) . uprintfs cs us uprintfs ('%':_) [] = errorMissingArgument uprintfs ('%':cs) us@(_:_) = fmt cs us uprintfs (c:cs) us = (c :) . uprintfs cs us -- Given a suffix of the format string starting just after -- the percent sign, and the list of remaining unprocessed -- arguments in the form described above, format the portion -- of the output described by this field description, and -- then continue with 'uprintfs'. fmt :: String -> [UPrintf] -> ShowS fmt cs0 us0 = case getSpecs False False Nothing False cs0 us0 of (_, _, []) -> errorMissingArgument (ufmt, cs, (_, u) : us) -> u ufmt . uprintfs cs us -- Given field formatting information, and a tuple -- consisting of a prefix (for example, a minus sign) that -- is supposed to go before the argument value and a string -- representing the value, return the properly padded and -- formatted result. adjust :: FieldFormat -> (String, String) -> String adjust ufmt (pre, str) = let naturalWidth = length pre + length str zero = case fmtAdjust ufmt of Just ZeroPad -> True _ -> False left = case fmtAdjust ufmt of Just LeftAdjust -> True _ -> False fill = case fmtWidth ufmt of Just width | naturalWidth < width -> let fillchar = if zero then '0' else ' ' in replicate (width - naturalWidth) fillchar _ -> "" in if left then pre ++ str ++ fill else if zero then pre ++ fill ++ str else fill ++ pre ++ str -- For positive numbers with an explicit sign field ("+" or -- " "), adjust accordingly. adjustSigned :: FieldFormat -> (String, String) -> String adjustSigned ufmt@(FieldFormat {fmtSign = Just SignPlus}) ("", str) = adjust ufmt ("+", str) adjustSigned ufmt@(FieldFormat {fmtSign = Just SignSpace}) ("", str) = adjust ufmt (" ", str) adjustSigned ufmt ps = adjust ufmt ps -- Format a signed integer in the "default" fashion. -- This will be subjected to adjust subsequently. fmti :: Maybe Int -> Integer -> (String, String) fmti prec i | i < 0 = ("-", integral_prec prec (show (-i))) | otherwise = ("", integral_prec prec (show i)) -- Format an unsigned integer in the "default" fashion. -- This will be subjected to adjust subsequently. The 'b' -- argument is the base, the 'pre' argument is the prefix, -- and the '(Just m)' argument is the implicit lower-bound -- size of the operand for conversion from signed to -- unsigned. Thus, this function will refuse to convert an -- unbounded negative integer to an unsigned string. fmtu :: Integer -> Maybe String -> Maybe Int -> Maybe Integer -> Integer -> (String, String) fmtu b (Just pre) prec m i = let ("", s) = fmtu b Nothing prec m i in case pre of "0" -> case s of '0' : _ -> ("", s) _ -> (pre, s) _ -> (pre, s) fmtu b Nothing prec0 m0 i0 = case fmtu' prec0 m0 i0 of Just s -> ("", s) Nothing -> errorBadArgument where fmtu' :: Maybe Int -> Maybe Integer -> Integer -> Maybe String fmtu' prec (Just m) i | i < 0 = fmtu' prec Nothing (-2 * m + i) fmtu' (Just prec) _ i | i >= 0 = fmap (integral_prec (Just prec)) $ fmtu' Nothing Nothing i fmtu' Nothing _ i | i >= 0 = Just $ showIntAtBase b intToDigit i "" fmtu' _ _ _ = Nothing -- This is used by 'fmtu' and 'fmti' to zero-pad an -- int-string to a required precision. integral_prec :: Maybe Int -> String -> String integral_prec Nothing integral = integral integral_prec (Just 0) "0" = "" integral_prec (Just prec) integral = replicate (prec - length integral) '0' ++ integral stoi :: String -> (Int, String) stoi cs = let (as, cs') = span isDigit cs in case as of "" -> (0, cs') _ -> (read as, cs') -- Figure out the FormatAdjustment, given: -- width, precision, left-adjust, zero-fill adjustment :: Maybe Int -> Maybe a -> Bool -> Bool -> Maybe FormatAdjustment adjustment w p l z = case w of Just n | n < 0 -> adjl p True z _ -> adjl p l z where adjl _ True _ = Just LeftAdjust adjl _ False True = Just ZeroPad adjl _ _ _ = Nothing -- Parse the various format controls to get a format specification. getSpecs :: Bool -> Bool -> Maybe FormatSign -> Bool -> String -> [UPrintf] -> (FieldFormat, String, [UPrintf]) getSpecs _ z s a ('-' : cs0) us = getSpecs True z s a cs0 us getSpecs l z _ a ('+' : cs0) us = getSpecs l z (Just SignPlus) a cs0 us getSpecs l z s a (' ' : cs0) us = getSpecs l z ss a cs0 us where ss = case s of Just SignPlus -> Just SignPlus _ -> Just SignSpace getSpecs l _ s a ('0' : cs0) us = getSpecs l True s a cs0 us getSpecs l z s _ ('#' : cs0) us = getSpecs l z s True cs0 us getSpecs l z s a ('*' : cs0) us = let (us', n) = getStar us ((p, cs''), us'') = case cs0 of '.':'*':r -> let (us''', p') = getStar us' in ((Just p', r), us''') '.':r -> let (p', r') = stoi r in ((Just p', r'), us') _ -> ((Nothing, cs0), us') FormatParse ms c cs = case us'' of (ufmt, _) : _ -> ufmt cs'' [] -> errorMissingArgument in (FieldFormat { fmtWidth = Just (abs n), fmtPrecision = p, fmtAdjust = adjustment (Just n) p l z, fmtSign = s, fmtAlternate = a, fmtModifiers = ms, fmtChar = c}, cs, us'') getSpecs l z s a ('.' : cs0) us = let ((p, cs'), us') = case cs0 of '*':cs'' -> let (us'', p') = getStar us in ((p', cs''), us'') _ -> (stoi cs0, us) FormatParse ms c cs = case us' of (ufmt, _) : _ -> ufmt cs' [] -> errorMissingArgument in (FieldFormat { fmtWidth = Nothing, fmtPrecision = Just p, fmtAdjust = adjustment Nothing (Just p) l z, fmtSign = s, fmtAlternate = a, fmtModifiers = ms, fmtChar = c}, cs, us') getSpecs l z s a cs0@(c0 : _) us | isDigit c0 = let (n, cs') = stoi cs0 ((p, cs''), us') = case cs' of '.' : '*' : r -> let (us'', p') = getStar us in ((Just p', r), us'') '.' : r -> let (p', r') = stoi r in ((Just p', r'), us) _ -> ((Nothing, cs'), us) FormatParse ms c cs = case us' of (ufmt, _) : _ -> ufmt cs'' [] -> errorMissingArgument in (FieldFormat { fmtWidth = Just (abs n), fmtPrecision = p, fmtAdjust = adjustment (Just n) p l z, fmtSign = s, fmtAlternate = a, fmtModifiers = ms, fmtChar = c}, cs, us') getSpecs l z s a cs0@(_ : _) us = let FormatParse ms c cs = case us of (ufmt, _) : _ -> ufmt cs0 [] -> errorMissingArgument in (FieldFormat { fmtWidth = Nothing, fmtPrecision = Nothing, fmtAdjust = adjustment Nothing Nothing l z, fmtSign = s, fmtAlternate = a, fmtModifiers = ms, fmtChar = c}, cs, us) getSpecs _ _ _ _ "" _ = errorShortFormat -- Process a star argument in a format specification. getStar :: [UPrintf] -> ([UPrintf], Int) getStar us = let ufmt = FieldFormat { fmtWidth = Nothing, fmtPrecision = Nothing, fmtAdjust = Nothing, fmtSign = Nothing, fmtAlternate = False, fmtModifiers = "", fmtChar = 'd' } in case us of [] -> errorMissingArgument (_, nu) : us' -> (us', read (nu ufmt "")) -- Format a RealFloat value. dfmt :: (RealFloat a) => Char -> Maybe Int -> Bool -> a -> (String, String) dfmt c p a d = let caseConvert = if isUpper c then map toUpper else id showFunction = case toLower c of 'e' -> showEFloat 'f' -> if a then showFFloatAlt else showFFloat 'g' -> if a then showGFloatAlt else showGFloat _ -> perror "internal error: impossible dfmt" result = caseConvert $ showFunction p d "" in case result of '-' : cs -> ("-", cs) cs -> ("" , cs) -- | Raises an 'error' with a printf-specific prefix on the -- message string. -- -- @since 4.7.0.0 perror :: String -> a perror s = errorWithoutStackTrace $ "printf: " ++ s -- | Calls 'perror' to indicate an unknown format letter for -- a given type. -- -- @since 4.7.0.0 errorBadFormat :: Char -> a errorBadFormat c = perror $ "bad formatting char " ++ show c errorShortFormat, errorMissingArgument, errorBadArgument :: a -- | Calls 'perror' to indicate that the format string ended -- early. -- -- @since 4.7.0.0 errorShortFormat = perror "formatting string ended prematurely" -- | Calls 'perror' to indicate that there is a missing -- argument in the argument list. -- -- @since 4.7.0.0 errorMissingArgument = perror "argument list ended prematurely" -- | Calls 'perror' to indicate that there is a type -- error or similar in the given argument. -- -- @since 4.7.0.0 errorBadArgument = perror "bad argument"