It's hard to tell what the best representation is if you don't know what the operations that you are going to perform are. If all you are going to do is I/O of bitstrings, then [Bool] could be great. If you need to do bitwise boolean ops then Integer is a wise choice. -- Lennart On Sep 14, 2006, at 21:35 , Thomas Conway wrote:
Hi all,
I'm doing some work with ASN.1, and I'm thinking about how to represent the type "BIT STRING".
The obvious, and inefficient representation would be
type BitString = [Bool]
A reasonable sparse representation might be
type BitString = [Integer] where the integers represent the positions of the non-zero bits, but other implementations (e.g. C & C++ based ones) mostly seem to use dense representations, and there are certain predictability advantages to be had by following existing implementations in this regard.
But given that a value of type BIT STRING is allowed to have leading 0 bits, which have no semantic effect, another representation would be
type BitString = [Word64] (I'm a modern type, and believe in 64bit computing ;-), but you could use Word32 if you liked).
However, after a few moments' consideration, I realized, that if I was going to use a representation like that, I could probably use
type BitString = Integer which already has [I assume] a carefully optimized implementation. Also, it ends up being significantly more strict than a list representation, which is probably a good thing in most situations.
My question for all present is: Have I missed either a problem with using Integer, or have I overlooked a better representation?
T. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe