[commit: integer-simple] master: Define testBitInteger; part of #3489. Patch from pumpkingod at gmail.com (d5ee098)

[Ian Lynagh]

Repository : ssh://darcs.haskell.org//srv/darcs/packages/integer-simple

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/d5ee098c0e801fbd2590a526c0cb30d5935a36fd

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

commit d5ee098c0e801fbd2590a526c0cb30d5935a36fd
Author: Ian Lynagh <ian at well-typed.com>
Date:   Sun Aug 5 15:56:00 2012 +0100

    Define testBitInteger; part of #3489. Patch from pumpkingod at gmail.com

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

 GHC/Integer.hs      |    2 +-
 GHC/Integer/Type.hs |    7 +++++++
 2 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/GHC/Integer.hs b/GHC/Integer.hs
index 4122d38..3bc8f16 100644
--- a/GHC/Integer.hs
+++ b/GHC/Integer.hs
@@ -33,7 +33,7 @@ module GHC.Integer (
     encodeDoubleInteger, decodeDoubleInteger, doubleFromInteger,
     -- gcdInteger, lcmInteger, -- XXX
     andInteger, orInteger, xorInteger, complementInteger,
-    shiftLInteger, shiftRInteger,
+    shiftLInteger, shiftRInteger, testInteger,
     hashInteger,
  ) where
 
diff --git a/GHC/Integer/Type.hs b/GHC/Integer/Type.hs
index 67ed19c..ee2c08f 100644
--- a/GHC/Integer/Type.hs
+++ b/GHC/Integer/Type.hs
@@ -314,6 +314,13 @@ shiftRInteger j@(Negative _) i
     = complementInteger (shiftRInteger (complementInteger j) i)
 shiftRInteger Naught         _ = Naught
 
+-- XXX this could be a lot more efficient, but this is a quick
+-- reimplementation of the default Data.Bits instance, so that we can
+-- implement the Integer interface
+testBitInteger :: Integer -> Int# -> Bool
+testBitInteger x i = (x `andInteger` (smallInteger 1# `shiftLInteger` i))
+        `neqInteger` smallInteger 0#
+
 twosComplementPositive :: Positive -> DigitsOnes
 twosComplementPositive p = flipBits (p `minusPositive` onePositive)