[project @ 2001-11-20 14:12:48 by simonpj]

Add constant-folding rules for Float# and Double#

ghc/lib/std/PrelFloat.lhs

 % ------------------------------------------------------------------------------
-% $Id: PrelFloat.lhs,v 1.13 2001/09/14 15:45:53 simonpj Exp $
+% $Id: PrelFloat.lhs,v 1.14 2001/11/20 14:12:48 simonpj Exp $
 %
 % (c) The University of Glasgow, 1994-2000
 %
@@ -768,6 +768,18 @@ minusFloat  (F# x) (F# y) = F# (minusFloat# x y)
 timesFloat  (F# x) (F# y) = F# (timesFloat# x y)
 divideFloat (F# x) (F# y) = F# (divideFloat# x y)
 
+{-# RULES
+"plusFloat x 0.0"   forall x#. plusFloat#  x#   0.0# = x#
+"plusFloat 0.0 x"   forall x#. plusFloat#  0.0# x#   = x#
+"minusFloat x 0.0"  forall x#. minusFloat# x#   0.0# = x#
+"minusFloat x x"    forall x#. minusFloat# x#   x#   = 0.0#
+"timesFloat x 0.0"  forall x#. timesFloat# x#   0.0# = 0.0#
+"timesFloat0.0 x"   forall x#. timesFloat# 0.0# x#   = 0.0#
+"timesFloat x 1.0"  forall x#. timesFloat# x#   1.0# = x#
+"timesFloat 1.0 x"  forall x#. timesFloat# 1.0# x#   = x#
+"divideFloat x 1.0" forall x#. divideFloat# x#  1.0# = x#
+  #-}
+
 negateFloat :: Float -> Float
 negateFloat (F# x)        = F# (negateFloat# x)
 
@@ -814,6 +826,18 @@ minusDouble  (D# x) (D# y) = D# (x -## y)
 timesDouble  (D# x) (D# y) = D# (x *## y)
 divideDouble (D# x) (D# y) = D# (x /## y)
 
+{-# RULES
+"plusDouble x 0.0"   forall x#. (+##) x#    0.0## = x#
+"plusDouble 0.0 x"   forall x#. (+##) 0.0## x#    = x#
+"minusDouble x 0.0"  forall x#. (-##) x#    0.0## = x#
+"minusDouble x x"    forall x#. (-##) x#    x#    = 0.0##
+"timesDouble x 0.0"  forall x#. (*##) x#    0.0## = 0.0##
+"timesDouble 0.0 x"  forall x#. (*##) 0.0## x#    = 0.0##
+"timesDouble x 1.0"  forall x#. (*##) x#    1.0## = x#
+"timesDouble 1.0 x"  forall x#. (*##) 1.0## x#    = x#
+"divideDouble x 1.0" forall x#. (/##) x#    1.0## = x#
+  #-}
+
 negateDouble :: Double -> Double
 negateDouble (D# x)        = D# (negateDouble# x)