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

    f = 0;

    for (i, c in b) {
        f += sign(t[i] ^ c);
    }

    f;
}

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

    for (, c in b) {
        e.append(drand(15) ? c : u[drand(26)]);
    }
}

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

    t = "METHINK IT IS LIKE A WEASEL";
    u = "ABCDEFGHIJKLMNOPQRSTUVWXYZ ";

    i = ~t;
    while (i) {
        i -= 1;
        b.append(u[drand(26)]);
    }

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

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

    return 0;
}