Rational#-

VALUE
rb_rational_minus(VALUE self, VALUE other)
{
    if (RB_INTEGER_TYPE_P(other)) {
        {
            get_dat1(self);

            return f_rational_new_no_reduce2(CLASS_OF(self),
                                             rb_int_minus(dat->num, rb_int_mul(other, dat->den)),
                                             dat->den);
        }
    }
    else if (RB_FLOAT_TYPE_P(other)) {
        return DBL2NUM(nurat_to_double(self) - RFLOAT_VALUE(other));
    }
    else if (RB_TYPE_P(other, T_RATIONAL)) {
        {
            get_dat2(self, other);

            return f_addsub(self,
                            adat->num, adat->den,
                            bdat->num, bdat->den, '-');
        }
    }
    else {
        return rb_num_coerce_bin(self, other, '-');
    }
}