integer
fitness(data t, data b)
{
    integer f, i;

    f = 0;

    i = b_length(t);
    while (i) {
        i -= 1;
        f += sign(t[i] ^ b[i]);
    }

    return f;
}

void
mutate(data c, data b, data u)
{
    integer i, l;

    l = b_length(b);
    i = 0;
    while (i < l) {
        if (drand(15)) {
            b_append(c, b[i]);
        } else {
            b_append(c, u[drand(26)]);
        }
        i += 1;
    }
}

integer
main(void)
{
    data b, t, u;
    integer f, i, l;

    b_cast(t, "METHINK IT IS LIKE A WEASEL");
    b_cast(u, "ABCDEFGHIJKLMNOPQRSTUVWXYZ ");

    l = b_length(t);

    i = l;
    while (i) {
        i -= 1;
        b_append(b, u[drand(26)]);
    }

    f = fitness(t, b);
    while (f) {
        data n;
        integer a;

        o_form("/lw4/~\n", f, b_string(b));

        n = b;

        i = 32;
        while (i) {
            data c;

            i -= 1;
            mutate(c, b, u);
            a = fitness(t, c);
            if (a < f) {
                f = a;
                n = c;
            }
        }

        b = n;
    }

    o_form("/lw4/~\n", f, b_string(b));

    return 0;
}