From 999f8cf9b4b8e39dc33d30de5b4478d52e3fe783 Mon Sep 17 00:00:00 2001
From: simonmar <unknown>
Date: Tue, 1 Apr 2003 09:35:13 +0000
Subject: [PATCH] [project @ 2003-04-01 09:35:13 by simonmar] Don't
 constant-fold (negateFloat# 0.0#), because the compiler's
 internal representation of floating-point literals
 (Rational) can't represent -0.0.  This means that

   main = print (-0.0)

now gives the same results with -O as it does without.

Fixes test arith005.
---
 ghc/compiler/prelude/PrelRules.lhs |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/ghc/compiler/prelude/PrelRules.lhs b/ghc/compiler/prelude/PrelRules.lhs
index 2c2a2e4..c13d6ed 100644
--- a/ghc/compiler/prelude/PrelRules.lhs
+++ b/ghc/compiler/prelude/PrelRules.lhs
@@ -208,10 +208,12 @@ cmpOp cmp l1 l2
 
 --------------------------
 
-negOp (MachFloat f)  = Just (mkFloatVal (-f))
-negOp (MachDouble d) = Just (mkDoubleVal (-d))
-negOp (MachInt i)    = intResult (-i)
-negOp l		     = Nothing
+negOp (MachFloat 0.0) = Nothing  -- can't represent -0.0 as a Rational
+negOp (MachFloat f)   = Just (mkFloatVal (-f))
+negOp (MachDouble 0.0) = Nothing
+negOp (MachDouble d)   = Just (mkDoubleVal (-d))
+negOp (MachInt i)      = intResult (-i)
+negOp l		       = Nothing
 
 --------------------------
 intOp2 op (MachInt i1) (MachInt i2) = intResult (i1 `op` i2)
-- 
1.7.10.4