Sum of all the bits in a Bit Vector of Z3

Question

Given a bit vector in Z3, I am wondering how can I sum up each individual bit of this vector?

E.g.,

a = BitVecVal(3, 2)
sum_all_bit(a) =         


        

Answer 1

It isn't part of the bit-vector operations. You can create an expression as follows:

def sub(b):
    n = b.size()
    bits = [ Extract(i, i, b) for i in range(n) ]
    bvs  = [ Concat(BitVecVal(0, n - 1), b) for b in bits ]
    nb   = reduce(lambda a, b: a + b, bvs)
    return nb


print sub(BitVecVal(4,7))

Of course, log(n) bits for the result will suffice if you prefer.