Skip to content

Remove bitcount; use popCount directly #1031

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Aug 31, 2024
Merged

Remove bitcount; use popCount directly #1031

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1 change: 0 additions & 1 deletion containers-tests/tests/IntSetValidity.hs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,6 @@ import Data.IntSet.Internal
import Data.List (intercalate)
import Numeric (showHex)
import Test.Tasty.QuickCheck (Property, counterexample, property, (.&&.))
import Utils.Containers.Internal.BitUtil (bitcount)

{--------------------------------------------------------------------
Assertions
Expand Down
2 changes: 1 addition & 1 deletion containers/src/Data/IntSet/Internal.hs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -367,7 +367,7 @@ size :: IntSet -> Int
size = go 0
where
go !acc (Bin _ l r) = go (go acc l) r
go acc (Tip _ bm) = acc + bitcount 0 bm
go acc (Tip _ bm) = acc + popCount bm
go acc Nil = acc

-- | \(O(\min(n,W))\). Is the value a member of the set?
Expand Down
29 changes: 2 additions & 27 deletions containers/src/Utils/Containers/Internal/BitUtil.hs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,7 +1,4 @@
{-# LANGUAGE CPP #-}
#if __GLASGOW_HASKELL__
{-# LANGUAGE MagicHash #-}
#endif
#if !defined(TESTING) && defined(__GLASGOW_HASKELL__)
{-# LANGUAGE Safe #-}
#endif
Expand Down Expand Up @@ -31,38 +28,16 @@
-- closely.

module Utils.Containers.Internal.BitUtil
( bitcount
, highestBitMask
( highestBitMask
, shiftLL
, shiftRL
, wordSize
) where

import Data.Bits (popCount, unsafeShiftL, unsafeShiftR
import Data.Bits (unsafeShiftL, unsafeShiftR
, countLeadingZeros, finiteBitSize
)


{----------------------------------------------------------------------
[bitcount] as posted by David F. Place to haskell-cafe on April 11, 2006,
based on the code on
http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetKernighan,
where the following source is given:
Published in 1988, the C Programming Language 2nd Ed. (by Brian W.
Kernighan and Dennis M. Ritchie) mentions this in exercise 2-9. On April
19, 2006 Don Knuth pointed out to me that this method "was first published
by Peter Wegner in CACM 3 (1960), 322. (Also discovered independently by
Derrick Lehmer and published in 1964 in a book edited by Beckenbach.)"
----------------------------------------------------------------------}

bitcount :: Int -> Word -> Int
bitcount a x = a + popCount x
{-# INLINE bitcount #-}

-- The highestBitMask implementation is based on
-- http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
-- which has been put in the public domain.

-- | Return a word where only the highest bit is set.
highestBitMask :: Word -> Word
highestBitMask w = shiftLL 1 (wordSize - 1 - countLeadingZeros w)
Expand Down