SYNOPSIS
        int last_bit(string str)

DESCRIPTION
        Return the number of the last set bit in bitstring <str>.

        Each character contains 6 bits. So you can store a value
        between 0 and 63 in one character (2^6=64). Starting character
        is the blank " " which has the value 0. The first character in
        the string is the one with the lowest bits (0-5).

EXAMPLES
        string s;

        s = set_bit("", 4); s = set_bit(s, 2);

        last_bit(s) --> returns 4

SEE ALSO
        set_bit(E), clear_bit(E), next_bit(E), test_bit(E), count_bits(E),
        and_bits(E), or_bits(E), xor_bits(E), invert_bits(E), copy_bits(E)