[commit: ghc] master: Use fromRational when pre-computing fromRational literals (6bb741b)

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/6bb741b12cf0829dd00fe9b16abc2941610cd155

>---------------------------------------------------------------

commit 6bb741b12cf0829dd00fe9b16abc2941610cd155
Author: Ian Lynagh <[email protected]>
Date:   Sun Oct 21 18:03:17 2012 +0100

    Use fromRational when pre-computing fromRational literals
    
    This makes it easier to be confident that the optimisation gives the
    right answer.

>---------------------------------------------------------------

 compiler/prelude/PrelRules.lhs |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/compiler/prelude/PrelRules.lhs b/compiler/prelude/PrelRules.lhs
index 2f4d62f..72cb878 100644
--- a/compiler/prelude/PrelRules.lhs
+++ b/compiler/prelude/PrelRules.lhs
@@ -50,6 +50,7 @@ import Util
 import Control.Monad
 import Data.Bits as Bits
 import Data.Int
+import Data.Ratio
 import Data.Word
 \end{code}
 
@@ -1177,7 +1178,7 @@ match_rationalTo mkLit _ _ id_unf [xl, yl]
   | Just (LitInteger x _) <- exprIsLiteral_maybe id_unf xl
   , Just (LitInteger y _) <- exprIsLiteral_maybe id_unf yl
   , y /= 0
-  = Just (mkLit (fromInteger x/fromInteger y))
+  = Just (mkLit (fromRational (x % y)))
 match_rationalTo _ _ _ _ _ = Nothing
 
 match_decodeDouble :: DynFlags