[GHC] #6135: Unboxed Booleans

[GHC]

#6135: Unboxed Booleans
---------------------------------+------------------------------------------
    Reporter:  benl              |       Owner:  jstolarek       
        Type:  feature request   |      Status:  patch           
    Priority:  normal            |   Milestone:  7.8.1           
   Component:  Compiler          |     Version:  7.4.1           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:  #605              |  
---------------------------------+------------------------------------------

Comment(by jstolarek):

 Following Ben's idea I created a proof-of-concept filter function using
 the new primops:

 {{{
 filterN :: Vector Int -> Vector Int
 filterN vec = runST $ do
   let !size = length vec
   fVec <- unsafeNew size
   let put i x = do
         let !(I# v) = x
             inc     = I# (v .>=# 0#)
         unsafeWrite fVec i x
         return $ i + inc
   fSize <- foldM' put 0 vec
   unsafeFreeze $ unsafeSlice 0 fSize fVec
 }}}

 Benchmarking with criterion shows that this function is 60% faster than
 the filter function based on stream fusion (tested for unboxed vectors
 containing 10 thousand and 10 million elements). Full code available
 [http://hackage.haskell.org/trac/ghc/wiki/PrimBool at the wiki page].

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6135#comment:29>
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