From be1ec6742c6ed6f2c1cc550f87e009be3ab45f78 Mon Sep 17 00:00:00 2001
From: simonmar <unknown>
Date: Wed, 29 Aug 2001 14:32:49 +0000
Subject: [PATCH] [project @ 2001-08-29 14:32:49 by simonmar] Fix *two* bugs
 in formatRealFloat:

The first one is in the Haskell 98 errata, namely that negative
exponents cause an infinite loop in the FFFixed case when no precision
is specified.  eg. `Numeric.showFFloat Nothing 0.02 ""'  I've modified
the code in the errata to properly handle the e == 0 case and to be
slightly more efficient when e > 0.

The second bug is this:

   Prelude> Numeric.showFFloat (Just 0) 0.02 ""
   "0."
---
 ghc/lib/std/PrelFloat.lhs |   22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/ghc/lib/std/PrelFloat.lhs b/ghc/lib/std/PrelFloat.lhs
index 67eb2a7..ef065a4 100644
--- a/ghc/lib/std/PrelFloat.lhs
+++ b/ghc/lib/std/PrelFloat.lhs
@@ -1,5 +1,5 @@
 % ------------------------------------------------------------------------------
-% $Id: PrelFloat.lhs,v 1.11 2001/02/28 00:01:03 qrczak Exp $
+% $Id: PrelFloat.lhs,v 1.12 2001/08/29 14:32:49 simonmar Exp $
 %
 % (c) The University of Glasgow, 1994-2000
 %
@@ -496,13 +496,15 @@ formatRealFloat fmt decs x
        mk0 ls = case ls of { "" -> "0" ; _ -> ls}
       in
       case decs of
-       Nothing ->
-         let
-	  f 0 s    rs  = mk0 (reverse s) ++ '.':mk0 rs
-	  f n s    ""  = f (n-1) ('0':s) ""
-	  f n s (r:rs) = f (n-1) (r:s) rs
-	 in
-	 f e "" ds
+       Nothing
+	  | e <= 0    -> "0." ++ replicate (-e) '0' ++ ds
+	  | otherwise ->
+	     let
+	  	f 0 s    rs  = mk0 (reverse s) ++ '.':mk0 rs
+	  	f n s    ""  = f (n-1) ('0':s) ""
+	  	f n s (r:rs) = f (n-1) (r:s) rs
+	     in
+	 	f e "" ds
        Just dec ->
         let dec' = max dec 0 in
 	if e >= 0 then
@@ -516,8 +518,8 @@ formatRealFloat fmt decs x
 	  (ei,is') = roundTo base dec' (replicate (-e) 0 ++ is)
 	  d:ds' = map intToDigit (if ei > 0 then is' else 0:is')
 	 in
-	 d : '.' : ds'
-	 
+	 d : (if null ds' then "" else '.':ds')
+
 
 roundTo :: Int -> Int -> [Int] -> (Int,[Int])
 roundTo base d is =
-- 
1.7.10.4