modulo

static VALUE
fix_mod(VALUE x, VALUE y)
{
    if (FIXNUM_P(y)) {
        long mod;

        fixdivmod(FIX2LONG(x), FIX2LONG(y), 0, &mod);
        return LONG2NUM(mod);
    }
    else if (RB_TYPE_P(y, T_BIGNUM)) {
        x = rb_int2big(FIX2LONG(x));
        return rb_big_modulo(x, y);
    }
    else if (RB_TYPE_P(y, T_FLOAT)) {
        return DBL2NUM(ruby_float_mod((double)FIX2LONG(x), RFLOAT_VALUE(y)));
    }
    else {
        return rb_num_coerce_bin(x, y, '%');
    }
}