A library for bit-vector arithmetic in Haskell

Bit-vectors are represented as a pair of a size and a value, where sizes are of type Int and values are Integer. Operations on bit-vectors are translated into operations on integers. Remarkably, most operations taking two or more bit-vectors, will perform zero-padding to adjust the size of the input bit-vectors when needed (eg. when adding bit-vectors of different sizes). Indexing operators don't do this, to avoid masking out of bounds errors.

Other libraries

There exist many Haskell libraries to handle bit-vectors, but to the best of my knowledge bv is the only one that adequately supports bit-vector arithmetic.

If you do not need bit-vector arithmetic, then you may consider using any of these other libraries, which could offer more compact and efficient implementations of bit arrays.

Importing and name clashes

Many exported functions name-clash with Prelude functions, it is therefore recommended to do a qualified import:

import           Data.BitVector ( BV )
import qualified Data.BitVector as BV

Running the test suite

If you wish to run the test suite simply:

cabal configure -ftest
cabal build

Then run:

dist/build/bv-tester/bv-tester

Performance

Tip: For best performance compile with -fgmp.

Tip: If you are brave enough, compile with -f -check-bounds (disables index bounds checking).

The BV datatype is simply a pair of an Int, to represent the size, and an arbitrary-precision Integer, to represent the value of a bit-vector. Both fields are strict, and we instruct GHC to unbox strict fields. Further, we ask GHC to inline virtually all bit-vector operations. When inlined, GHC should be able to remove any overhead associated with the BV data type, and unbox bit-vector sizes. Performance should depend mostly on the Integer data type implementation.