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module PreludeText (
reads, shows, show, read, lex,
showChar, showString, readParen, showParen, readLitChar, showLitChar,
readSigned, showSigned, readDec, showInt, readFloat, showFloat ) where
{-#Prelude#-} -- Indicates definitions of compiler prelude symbols
reads :: (Text a) => ReadS a
reads = readsPrec 0
shows :: (Text a) => a -> ShowS
shows = showsPrec 0
read :: (Text a) => String -> a
read s = case [x | (x,t) <- reads s, ("","") <- lex t] of
[x] -> x
[] -> error "read{PreludeText}: no parse"
_ -> error "read{PreludeText}: ambiguous parse"
show :: (Text a) => a -> String
show x = shows x ""
showChar :: Char -> ShowS
showChar = (:)
showString :: String -> ShowS
showString = (++)
showParen :: Bool -> ShowS -> ShowS
showParen b p = if b then showChar '(' . p . showChar ')' else p
readParen :: Bool -> ReadS a -> ReadS a
readParen b g = if b then mandatory else optional
where optional r = g r ++ mandatory r
mandatory r = [(x,u) | ("(",s) <- lex r,
(x,t) <- optional s,
(")",u) <- lex t ]
lex :: ReadS String
lex "" = [("","")]
lex (c:s) | isSpace c = lex (dropWhile isSpace s)
lex ('-':'-':s) = case dropWhile (/= '\n') s of
'\n':t -> lex t
_ -> [] -- unterminated end-of-line
-- comment
lex ('{':'-':s) = lexNest lex s
where
lexNest f ('-':'}':s) = f s
lexNest f ('{':'-':s) = lexNest (lexNest f) s
lexNest f (c:s) = lexNest f s
lexNest _ "" = [] -- unterminated
-- nested comment
lex ('<':'-':s) = [("<-",s)]
lex ('\'':s) = [('\'':ch++"'", t) | (ch,'\'':t) <- lexLitChar s,
ch /= "'" ]
lex ('"':s) = [('"':str, t) | (str,t) <- lexString s]
where
lexString ('"':s) = [("\"",s)]
lexString s = [(ch++str, u)
| (ch,t) <- lexStrItem s,
(str,u) <- lexString t ]
lexStrItem ('\\':'&':s) = [("\\&",s)]
lexStrItem ('\\':c:s) | isSpace c
= [("\\&",t) | '\\':t <- [dropWhile isSpace s]]
lexStrItem s = lexLitChar s
lex (c:s) | isSingle c = [([c],s)]
| isSym1 c = [(c:sym,t) | (sym,t) <- [span isSym s]]
| isAlpha c = [(c:nam,t) | (nam,t) <- [span isIdChar s]]
| isDigit c = [(c:ds++fe,t) | (ds,s) <- [span isDigit s],
(fe,t) <- lexFracExp s ]
| otherwise = [] -- bad character
where
isSingle c = c `elem` ",;()[]{}_"
isSym1 c = c `elem` "-~" || isSym c
isSym c = c `elem` "!@#$%&*+./<=>?\\^|:"
isIdChar c = isAlphanum c || c `elem` "_'"
lexFracExp ('.':s) = [('.':ds++e,u) | (ds,t) <- lexDigits s,
(e,u) <- lexExp t ]
lexFracExp s = [("",s)]
lexExp (e:s) | e `elem` "eE"
= [(e:c:ds,u) | (c:t) <- [s], c `elem` "+-",
(ds,u) <- lexDigits t] ++
[(e:ds,t) | (ds,t) <- lexDigits s]
lexExp s = [("",s)]
lexDigits :: ReadS String
lexDigits = nonnull isDigit
nonnull :: (Char -> Bool) -> ReadS String
nonnull p s = [(cs,t) | (cs@(_:_),t) <- [span p s]]
lexLitChar :: ReadS String
lexLitChar ('\\':s) = [('\\':esc, t) | (esc,t) <- lexEsc s]
where
lexEsc (c:s) | c `elem` "abfnrtv\\\"'" = [([c],s)]
lexEsc ('^':c:s) | c >= '@' && c <= '_' = [(['^',c],s)]
lexEsc s@(d:_) | isDigit d = lexDigits s
lexEsc ('o':s) = [('o':os, t) | (os,t) <- nonnull isOctDigit s]
lexEsc ('x':s) = [('x':xs, t) | (xs,t) <- nonnull isHexDigit s]
lexEsc s@(c:_) | isUpper c
= case [(mne,s') | mne <- "DEL" : elems asciiTab,
([],s') <- [match mne s] ]
of (pr:_) -> [pr]
[] -> []
lexEsc _ = []
lexLitChar (c:s) = [([c],s)]
lexLitChar "" = []
isOctDigit c = c >= '0' && c <= '7'
isHexDigit c = isDigit c || c >= 'A' && c <= 'F'
|| c >= 'a' && c <= 'f'
match :: (Eq a) => [a] -> [a] -> ([a],[a])
match (x:xs) (y:ys) | x == y = match xs ys
match xs ys = (xs,ys)
asciiTab = 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"]
readLitChar :: ReadS Char
readLitChar ('\\':s) = readEsc s
where
readEsc ('a':s) = [('\a',s)]
readEsc ('b':s) = [('\b',s)]
readEsc ('f':s) = [('\f',s)]
readEsc ('n':s) = [('\n',s)]
readEsc ('r':s) = [('\r',s)]
readEsc ('t':s) = [('\t',s)]
readEsc ('v':s) = [('\v',s)]
readEsc ('\\':s) = [('\\',s)]
readEsc ('"':s) = [('"',s)]
readEsc ('\'':s) = [('\'',s)]
readEsc ('^':c:s) | c >= '@' && c <= '_'
= [(chr (ord c - ord '@'), s)]
readEsc s@(d:_) | isDigit d
= [(chr n, t) | (n,t) <- readDec s]
readEsc ('o':s) = [(chr n, t) | (n,t) <- readOct s]
readEsc ('x':s) = [(chr n, t) | (n,t) <- readHex s]
readEsc s@(c:_) | isUpper c
= let table = ('\DEL' := "DEL") : assocs asciiTab
in case [(c,s') | (c := mne) <- table,
([],s') <- [match mne s]]
of (pr:_) -> [pr]
[] -> []
readEsc _ = []
readLitChar (c:s) = [(c,s)]
showLitChar :: Char -> ShowS
showLitChar c | c > '\DEL' = showChar '\\' . protectEsc isDigit (shows (ord c))
showLitChar '\DEL' = showString "\\DEL"
showLitChar '\\' = showString "\\\\"
showLitChar c | c >= ' ' = showChar c
showLitChar '\a' = showString "\\a"
showLitChar '\b' = showString "\\b"
showLitChar '\f' = showString "\\f"
showLitChar '\n' = showString "\\n"
showLitChar '\r' = showString "\\r"
showLitChar '\t' = showString "\\t"
showLitChar '\v' = showString "\\v"
showLitChar '\SO' = protectEsc (== 'H') (showString "\\SO")
showLitChar c = showString ('\\' : asciiTab!c)
protectEsc p f = f . cont
where cont s@(c:_) | p c = "\\&" ++ s
cont s = s
readDec, readOct, readHex :: (Integral a) => ReadS a
readDec = readInt 10 isDigit (\d -> ord d - ord '0')
readOct = readInt 8 isOctDigit (\d -> ord d - ord '0')
readHex = readInt 16 isHexDigit hex
where hex d = ord d - (if isDigit d then ord '0'
else ord (if isUpper d then 'A' else 'a')
- 10)
readInt :: (Integral a) => a -> (Char -> Bool) -> (Char -> Int) -> ReadS a
readInt radix isDig digToInt s =
[(foldl1 (\n d -> n * radix + d) (map (fromIntegral . digToInt) ds), r)
| (ds,r) <- nonnull isDig s ]
showInt :: (Integral a) => a -> ShowS
showInt n r = let (n',d) = quotRem n 10
r' = chr (ord '0' + fromIntegral d) : r
in if n' == 0 then r' else showInt n' r'
readSigned:: (Real a) => ReadS a -> ReadS a
readSigned readPos = readParen False read'
where read' r = read'' r ++
[(-x,t) | ("-",s) <- lex r,
(x,t) <- read'' s]
read'' r = [(n,s) | (str,s) <- lex r,
(n,"") <- readPos str]
showSigned:: (Real a) => (a -> ShowS) -> Int -> a -> ShowS
showSigned showPos p x = if x < 0 then showParen (p > 6)
(showChar '-' . showPos (-x))
else showPos x
-- The functions readFloat and showFloat below use rational arithmetic
-- to insure correct conversion between the floating-point radix and
-- decimal. It is often possible to use a higher-precision floating-
-- point type to obtain the same results.
readFloat:: (RealFloat a) => ReadS a
readFloat r = [(fromRational ((n%1)*10^^(k-d)), t) | (n,d,s) <- readFix r,
(k,t) <- readExp s]
where readFix r = [(read (ds++ds'), length ds', t)
| (ds,'.':s) <- lexDigits r,
(ds',t) <- lexDigits s ]
readExp (e:s) | e `elem` "eE" = readExp' s
readExp s = [(0,s)]
readExp' ('-':s) = [(-k,t) | (k,t) <- readDec s]
readExp' ('+':s) = readDec s
readExp' s = readDec s
-- The number of decimal digits m below is chosen to guarantee
-- read (show x) == x. See
-- Matula, D. W. A formalization of floating-point numeric base
-- conversion. IEEE Transactions on Computers C-19, 8 (1970 August),
-- 681-692.
showFloat:: (RealFloat a) => a -> ShowS
showFloat x =
if x == 0 then showString ("0." ++ take (m-1) (repeat '0'))
else if e >= m-1 || e < 0 then showSci else showFix
where
showFix = showString whole . showChar '.' . showString frac
where (whole,frac) = splitAt (e+1) (show sig)
showSci = showChar d . showChar '.' . showString frac
. showChar 'e' . shows e
where (d:frac) = show sig
(m, sig, e) = if b == 10 then (w, s, n+w-1)
else (m', sig', e' )
m' = ceiling
(fromIntegral w * log (fromInteger b) / log 10 :: Double)
+ 1
(sig', e') = if sig1 >= 10^m' then (round (t/10), e1+1)
else if sig1 < 10^(m'-1) then (round (t*10), e1-1)
else (sig1, e1 )
sig1 :: Integer
sig1 = round t
t = s%1 * (b%1)^^n * 10^^(m'-e1-1)
e1 = floor (logBase 10 x)
(s, n) = decodeFloat x
b = floatRadix x
w = floatDigits x
|
