Hi,

I'm fiddling with some little project where I need to count the number
of bits that are the same between two bitstrings. My first
approximation would be to bitXnor: both integers and count bits in the
result. However, there's no bitXnor: and the standard implementation:

a XNOR b = (a AND b) OR (NOT a AND NOT b)

won't fly because there's not bitNot in Integer, as far as I can tell
(negate draws in all the ugliness of 2-complement arithmetic :)).

It's probably a stupid question that only shows how rusty my bit
fiddling is - but what would be a *good* performing implementation of
something that counts matching bits? (for extra credits: if the two
integers are unequal in size, it's a pattern match so the smaller int
needs to be shifted along the larger int and the largest count is the
one that's returned):

011101 / 101 -> 3
011111 / 101 -> 2
0101 / 0001 -> 3
... etcetera)

-- 
"Human beings make life so interesting. Do you know, that in a
universe so full of wonders, they have managed to invent boredom. " -
Death, in "The Hogfather"