Re: [GHC] #7860: Add more bit fiddling functions to 'integer-gmp'

9 Jun 2013

      #7860: Add more bit fiddling functions to 'integer-gmp'
--------------------------------+-------------------------------------------
  Reporter:  lebedev            |          Owner:                  
      Type:  feature request    |         Status:  new             
  Priority:  normal             |      Milestone:                  
 Component:  libraries (other)  |        Version:  7.6.3           
Resolution:                     |       Keywords:  gmp             
        Os:  Unknown/Multiple   |   Architecture:  Unknown/Multiple
   Failure:  None/Unknown       |     Difficulty:  Unknown         
  Testcase:                     |      Blockedby:                  
  Blocking:                     |        Related:  #3489           
--------------------------------+-------------------------------------------

Comment(by lebedev):

 Actually, there should also be a case for negative bits, so the full
 version is:

 {{{
 clearBitInteger :: Integer -> Int# -> Integer
 clearBitInteger (S# j) i
     | i <# 0# || i >=# (WORD_SIZE_IN_BITS# -# 1#) = S# j
     | otherwise =
         let !mask =
                 int2Word# (1# `uncheckedIShiftL#` i) `xor#`
                 int2Word# (negateInt# 1#)
         in S# (word2Int# (int2Word# j `and#` mask))
 clearBitInteger (J# s d) i =
     let !(# s', d' #) = clearBitInteger# s d i in J# s' d'
 }}}

-- 
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7860#comment:8
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