-----------------------------------------------------------------------------
-- |
-- Module : Text.Printf
-- Copyright : (c) Lennart Augustsson, 2004
-- License : BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer : lennart@augustsson.net
-- Stability : provisional
-- Portability : portable
--
-- A C printf like formatter.
--
-----------------------------------------------------------------------------
module Text.Printf(
printf, hPrintf,
PrintfType, HPrintfType, PrintfArg, IsChar
) where
import Prelude
import Data.Char
import Data.Int
import Data.Word
import Numeric(showEFloat, showFFloat, showGFloat)
import System.IO
-------------------
-- | Format a variable number of arguments with the C-style formatting string.
-- The return value is either 'String' or @('IO' a)@.
--
-- 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 conversion specification begins with the
-- character @%@, followed by one or more of the following flags:
--
-- > - left adjust (default is right adjust)
-- > + always use a sign (+ or -) for signed conversions
-- > 0 pad with zeroes rather than spaces
--
-- followed optionally by a field width:
--
-- > num field width
-- > * as num, but taken from argument list
--
-- followed optionally by a precision:
--
-- > .num precision (number of decimal places)
--
-- and finally, a format character:
--
-- > c character Char, Int, Integer, ...
-- > d decimal Char, Int, Integer, ...
-- > o octal Char, Int, Integer, ...
-- > x hexadecimal Char, Int, Integer, ...
-- > X hexadecimal Char, Int, Integer, ...
-- > u unsigned decimal Char, Int, Integer, ...
-- > f floating point Float, Double
-- > g general format float Float, Double
-- > G general format float Float, Double
-- > e exponent format float Float, Double
-- > E exponent format float Float, Double
-- > s string String
--
-- Mismatch between the argument types and the format string will cause
-- an exception to be thrown at runtime.
--
-- Examples:
--
-- > > printf "%d\n" (23::Int)
-- > 23
-- > > printf "%s %s\n" "Hello" "World"
-- > Hello World
-- > > printf "%.2f\n" pi
-- > 3.14
--
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 98
instance PrintfType String where
spr fmt args = uprintf fmt (reverse args)
-}
instance (IsChar c) => PrintfType [c] where
spr fmts args = map fromChar (uprintf fmts (reverse args))
instance PrintfType (IO a) where
spr fmts args = do
putStr (uprintf fmts (reverse args))
return undefined
instance HPrintfType (IO a) where
hspr hdl fmts args = do
hPutStr hdl (uprintf fmts (reverse args))
return undefined
instance (PrintfArg a, PrintfType r) => PrintfType (a -> r) where
spr fmts args = \ a -> spr fmts (toUPrintf a : args)
instance (PrintfArg a, HPrintfType r) => HPrintfType (a -> r) where
hspr hdl fmts args = \ a -> hspr hdl fmts (toUPrintf a : args)
class PrintfArg a where
toUPrintf :: a -> UPrintf
instance PrintfArg Char where
toUPrintf c = UChar c
{- not allowed in Haskell 98
instance PrintfArg String where
toUPrintf s = UString s
-}
instance (IsChar c) => PrintfArg [c] where
toUPrintf = UString . map toChar
instance PrintfArg Int where
toUPrintf = uInteger
instance PrintfArg Int8 where
toUPrintf = uInteger
instance PrintfArg Int16 where
toUPrintf = uInteger
instance PrintfArg Int32 where
toUPrintf = uInteger
instance PrintfArg Int64 where
toUPrintf = uInteger
#ifndef __NHC__
instance PrintfArg Word where
toUPrintf = uInteger
#endif
instance PrintfArg Word8 where
toUPrintf = uInteger
instance PrintfArg Word16 where
toUPrintf = uInteger
instance PrintfArg Word32 where
toUPrintf = uInteger
instance PrintfArg Word64 where
toUPrintf = uInteger
instance PrintfArg Integer where
toUPrintf = UInteger 0
instance PrintfArg Float where
toUPrintf = UFloat
instance PrintfArg Double where
toUPrintf = UDouble
uInteger :: (Integral a, Bounded a) => a -> UPrintf
uInteger x = UInteger (toInteger $ minBound `asTypeOf` x) (toInteger x)
class IsChar c where
toChar :: c -> Char
fromChar :: Char -> c
instance IsChar Char where
toChar c = c
fromChar c = c
-------------------
data UPrintf = UChar Char | UString String | UInteger Integer Integer | UFloat Float | UDouble Double
uprintf :: String -> [UPrintf] -> String
uprintf "" [] = ""
uprintf "" (_:_) = fmterr
uprintf ('%':'%':cs) us = '%':uprintf cs us
uprintf ('%':_) [] = argerr
uprintf ('%':cs) us@(_:_) = fmt cs us
uprintf (c:cs) us = c:uprintf cs us
fmt :: String -> [UPrintf] -> String
fmt cs us =
let (width, prec, ladj, zero, plus, cs', us') = getSpecs False False False cs us
adjust (pre, str) =
let lstr = length str
lpre = length pre
fill = if lstr+lpre < width then take (width-(lstr+lpre)) (repeat (if zero then '0' else ' ')) else ""
in if ladj then pre ++ str ++ fill else if zero then pre ++ fill ++ str else fill ++ pre ++ str
adjust' ("", str) | plus = adjust ("+", str)
adjust' ps = adjust ps
in
case cs' of
[] -> fmterr
c:cs'' ->
case us' of
[] -> argerr
u:us'' ->
(case c of
'c' -> adjust ("", [toEnum (toint u)])
'd' -> adjust' (fmti u)
'i' -> adjust' (fmti u)
'x' -> adjust ("", fmtu 16 u)
'X' -> adjust ("", map toUpper $ fmtu 16 u)
'o' -> adjust ("", fmtu 8 u)
'u' -> adjust ("", fmtu 10 u)
'e' -> adjust' (dfmt' c prec u)
'E' -> adjust' (dfmt' c prec u)
'f' -> adjust' (dfmt' c prec u)
'g' -> adjust' (dfmt' c prec u)
'G' -> adjust' (dfmt' c prec u)
's' -> adjust ("", tostr u)
_ -> perror ("bad formatting char " ++ [c])
) ++ uprintf cs'' us''
fmti :: UPrintf -> (String, String)
fmti (UInteger _ i) = if i < 0 then ("-", show (-i)) else ("", show i)
fmti (UChar c) = fmti (uInteger (fromEnum c))
fmti _ = baderr
fmtu :: Integer -> UPrintf -> String
fmtu b (UInteger l i) = itosb b (if i < 0 then -2*l + i else i)
fmtu b (UChar c) = itosb b (toInteger (fromEnum c))
fmtu _ _ = baderr
toint :: UPrintf -> Int
toint (UInteger _ i) = fromInteger i
toint (UChar c) = fromEnum c
toint _ = baderr
tostr :: UPrintf -> String
tostr (UString s) = s
tostr _ = baderr
itosb :: Integer -> Integer -> String
itosb b n =
if n < b then
[intToDigit $ fromInteger n]
else
let (q, r) = quotRem n b in
itosb b q ++ [intToDigit $ fromInteger r]
stoi :: Int -> String -> (Int, String)
stoi a (c:cs) | isDigit c = stoi (a*10 + digitToInt c) cs
stoi a cs = (a, cs)
getSpecs :: Bool -> Bool -> Bool -> String -> [UPrintf] -> (Int, Int, Bool, Bool, Bool, String, [UPrintf])
getSpecs _ z s ('-':cs) us = getSpecs True z s cs us
getSpecs l z _ ('+':cs) us = getSpecs l z True cs us
getSpecs l _ s ('0':cs) us = getSpecs l True s cs us
getSpecs l z s ('*':cs) us =
case us of
[] -> argerr
nu : us' ->
let n = toint nu
(p, cs'', us'') =
case cs of
'.':'*':r -> case us' of { [] -> argerr; pu:us''' -> (toint pu, r, us''') }
'.':r -> let (n', cs') = stoi 0 r in (n', cs', us')
_ -> (-1, cs, us')
in (n, p, l, z, s, cs'', us'')
getSpecs l z s ('.':cs) us =
let (p, cs') = stoi 0 cs
in (0, p, l, z, s, cs', us)
getSpecs l z s cs@(c:_) us | isDigit c =
let (n, cs') = stoi 0 cs
(p, cs'') = case cs' of
'.':r -> stoi 0 r
_ -> (-1, cs')
in (n, p, l, z, s, cs'', us)
getSpecs l z s cs us = (0, -1, l, z, s, cs, us)
dfmt' :: Char -> Int -> UPrintf -> (String, String)
dfmt' c p (UDouble d) = dfmt c p d
dfmt' c p (UFloat f) = dfmt c p f
dfmt' _ _ _ = baderr
dfmt :: (RealFloat a) => Char -> Int -> a -> (String, String)
dfmt c p d =
case (if isUpper c then map toUpper else id) $
(case toLower c of
'e' -> showEFloat
'f' -> showFFloat
'g' -> showGFloat
_ -> error "Printf.dfmt: impossible"
)
(if p < 0 then Nothing else Just p) d "" of
'-':cs -> ("-", cs)
cs -> ("" , cs)
perror :: String -> a
perror s = error ("Printf.printf: "++s)
fmterr, argerr, baderr :: a
fmterr = perror "formatting string ended prematurely"
argerr = perror "argument list ended prematurely"
baderr = perror "bad argument"
|
