-
-#if __GLASGOW_HASKELL__ >= 504
--- The readFloat in the Numeric library will do the job
-
-readFloat :: (RealFrac a) => ReadS a
-readFloat = Numeric.readFloat
-
-#else
--- Haskell 98's Numeric.readFloat used to have a bogusly restricted signature
--- so it was incapable of reading a rational.
--- So for GHCs that have that old bogus library, here is the code, written out longhand.
-
-readFloat r = [(fromRational ((n%1)*10^^(k-d)),t) | (n,d,s) <- readFix r,
- (k,t) <- readExp s] ++
- [ (0/0, t) | ("NaN",t) <- lex r] ++
- [ (1/0, t) | ("Infinity",t) <- lex r]
- where
- readFix r = [(read (ds++ds'), length ds', t)
- | (ds,d) <- lexDigits r,
- (ds',t) <- lexFrac d ]
-
- lexFrac ('.':ds) = lexDigits ds
- lexFrac s = [("",s)]
-
- readExp (e:s) | e `elem` "eE" = readExp' s
- readExp s = [(0,s)]
-
- readExp' ('-':s) = [(-k,t) | (k,t) <- Numeric.readDec s]
- readExp' ('+':s) = Numeric.readDec s
- readExp' s = Numeric.readDec s
-
-lexDigits :: ReadS String
-lexDigits s = case span isDigit s of
- (cs,s') | not (null cs) -> [(cs,s')]
- otherwise -> []
-#endif