Date.ordinal

static VALUE
date_s_ordinal(int argc, VALUE *argv, VALUE klass)
{
    VALUE vy, vd, vsg, y, fr, fr2, ret;
    int d;
    double sg;

    rb_scan_args(argc, argv, "03", &vy, &vd, &vsg);

    y = INT2FIX(-4712);
    d = 1;
    fr2 = INT2FIX(0);
    sg = DEFAULT_SG;

    switch (argc) {
      case 3:
        val2sg(vsg, sg);
      case 2:
        check_numeric(vd, "yday");
        num2int_with_frac(d, positive_inf);
      case 1:
        check_numeric(vy, "year");
        y = vy;
    }

    {
        VALUE nth;
        int ry, rd, rjd, ns;

        if (!valid_ordinal_p(y, d, sg,
                             &nth, &ry,
                             &rd, &rjd,
                             &ns))
            rb_raise(eDateError, "invalid date");

        ret = d_simple_new_internal(klass,
                                     nth, rjd,
                                     sg,
                                     0, 0, 0,
                                     HAVE_JD);
    }
    add_frac();
    return ret;
}