weeknum

static VALUE
date_s_weeknum(int argc, VALUE *argv, VALUE klass)
{
    VALUE vy, vw, vd, vf, vsg, y, fr, fr2, ret;
    int w, d, f;
    double sg;

    rb_scan_args(argc, argv, "05", &vy, &vw, &vd, &vf, &vsg);

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

    switch (argc) {
      case 5:
        val2sg(vsg, sg);
      case 4:
        f = NUM2INT(vf);
      case 3:
        num2int_with_frac(d, positive_inf);
      case 2:
        w = NUM2INT(vw);
      case 1:
        y = vy;
    }

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

        if (!valid_weeknum_p(y, w, d, f, sg,
                             &nth, &ry,
                             &rw, &rd, &rjd,
                             &ns))
            rb_raise(rb_eArgError, "invalid date");

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