odd?

static VALUE
int_odd_p(VALUE num)
{
    if (FIXNUM_P(num)) {
        if (num & 2) {
            return Qtrue;
        }
    }
    else if (RB_TYPE_P(num, T_BIGNUM)) {
        return rb_big_odd_p(num);
    }
    else if (rb_funcall(num, '%', 1, INT2FIX(2)) != INT2FIX(0)) {
        return Qtrue;
    }
    return Qfalse;
}