[project @ 1999-01-19 11:44:07 by sof]

[ghc-hetmet.git] / ghc / lib / std / PrelNumExtra.lhs

diff --git a/ghc/lib/std/PrelNumExtra.lhs b/ghc/lib/std/PrelNumExtra.lhs
index 274b36e..5ba5ebd 100644 (file)
--- a/ghc/lib/std/PrelNumExtra.lhs
+++ b/ghc/lib/std/PrelNumExtra.lhs
@@ -517,9 +517,22 @@ normalize r = if r < 1 then
                    tn = 10^n
                in  if x >= tn then norm ee (x/tn) (e+n) else norm (ee-1) x e
 
-drop0 :: String -> String
-drop0 "" = ""
-drop0 (c:cs) = c : fromMaybe [] (dropTrailing0s cs) --WAS (yuck): reverse (dropWhile (=='0') (reverse cs))
+prR :: Int -> Rational -> Int -> String
+prR n r e  | r <  1  = prR n (r*10) (e-1)              -- final adjustment
+prR n r e  | r >= 10 = prR n (r/10) (e+1)
+prR n r e0
+  | e > 0 && e < 8   = takeN e s ('.' : drop0 (drop e s) [])
+  | e <= 0 && e > -3 = '0': '.' : takeN (-e) (repeat '0') (drop0 s [])
+  | otherwise       =  h : '.' : drop0 t ('e':show e0)
+   where
+       s@(h:t) = show ((round (r * 10^n))::Integer)
+       e       = e0+1
+       
+       takeN (I# n#) ls rs = takeUInt n# ls rs
+
+drop0 :: String -> String -> String
+drop0     [] rs = rs
+drop0 (c:cs) rs = c : fromMaybe rs (dropTrailing0s cs) --WAS (yuck): reverse (dropWhile (=='0') (reverse cs))
   where
    dropTrailing0s []       = Nothing
    dropTrailing0s ('0':xs) = 
@@ -531,18 +544,6 @@ drop0 (c:cs) = c : fromMaybe [] (dropTrailing0s cs) --WAS (yuck): reverse (dropW
       Nothing -> Just [x]
       Just ls -> Just (x:ls)
 
-prR :: Int -> Rational -> Int -> String
-prR n r e | r <  1  = prR n (r*10) (e-1)               -- final adjustment
-prR n r e | r >= 10 = prR n (r/10) (e+1)
-prR n r e0 =
-       let s = show ((round (r * 10^n))::Integer)
-           e = e0+1
-       in  if e > 0 && e < 8 then
-               take e s ++ "." ++ drop0 (drop e s)
-           else if e <= 0 && e > -3 then
-               "0." ++ take (-e) (repeat '0') ++ drop0 s
-           else
-               head s : "."++ drop0 (tail s) ++ "e" ++ show e0
 \end{code}
 
 [In response to a request for documentation of how fromRational works,
@@ -712,7 +713,7 @@ formatRealFloat fmt decs x
        Just dec ->
         let dec' = max dec 1 in
         case is of
-         [0] -> '0':'.':take dec' (repeat '0') ++ "e0"
+         [0] -> '0' :'.' : take dec' (repeat '0') ++ "e0"
          _ ->
           let
           (ei,is') = roundTo base (dec'+1) is