Enumerator::ArithmeticSequence#size

static VALUE
arith_seq_size(VALUE self)
{
    VALUE b, e, s, len_1, len, last;
    int x;

    b = arith_seq_begin(self);
    e = arith_seq_end(self);
    s = arith_seq_step(self);
    x = arith_seq_exclude_end_p(self);

    if (RB_FLOAT_TYPE_P(b) || RB_FLOAT_TYPE_P(e) || RB_FLOAT_TYPE_P(s)) {
        double ee, n;

        if (NIL_P(e)) {
            if (rb_num_negative_int_p(s)) {
                ee = -HUGE_VAL;
            }
            else {
                ee = HUGE_VAL;
            }
        }
        else {
            ee = NUM2DBL(e);
        }

        n = ruby_float_step_size(NUM2DBL(b), ee, NUM2DBL(s), x);
        if (isinf(n)) return DBL2NUM(n);
        if (POSFIXABLE(n)) return LONG2FIX((long)n);
        return rb_dbl2big(n);
    }

    if (NIL_P(e)) {
        return DBL2NUM(HUGE_VAL);
    }

    if (!rb_obj_is_kind_of(s, rb_cNumeric)) {
        s = rb_to_int(s);
    }

    if (rb_equal(s, INT2FIX(0))) {
        return DBL2NUM(HUGE_VAL);
    }

    len_1 = rb_int_idiv(rb_int_minus(e, b), s);
    if (rb_num_negative_int_p(len_1)) {
        return INT2FIX(0);
    }

    last = rb_int_plus(b, rb_int_mul(s, len_1));
    if (x && rb_equal(last, e)) {
        len = len_1;
    }
    else {
        len = rb_int_plus(len_1, INT2FIX(1));
    }

    return len;
}