[RUBY] Behavior when each is executed in the reverse order Range

When I turned each, I did nothing and did not get an error, and I was addicted to it because the processing continued as it was, so I made a memorandum.

Range instantiation

Instances can be created without problems in either case of start point <end point, start point> end point.

aaa = Range.new(1,5)
=> 1..5

bbb = 1..5
=> 1..5

ccc = Range.new(5,1)
=> 5..1

ddd = 5..1
=> 5..1

Range#each

Range # each behavior

The problem is when you turn each in the Range generated in reverse order.

aaa.each {|i| puts i}
1
2
3
4
5
=> 1..5

ccc.each {|i|puts i}
=> 5..1

Description of Range # each

According to Rurima, Range # each is iterated with succ. https://docs.ruby-lang.org/ja/latest/method/Range/i/each.html

Looking at the description of succ for Integer, it seems that it simply returns the next integer.

aaa.begin.class
=> Integer

https://docs.ruby-lang.org/ja/2.5.0/method/Integer/i/next.html

aaa.begin
=> 1
aaa.begin.succ
=> 2

ccc.begin
=> 5
ccc.begin.succ
=> 6

Implementation of Range # each

Probably static VALUE range_each (VALUE range) is called, and since the while condition is not satisfied after that, it seems that the processing is completed without looping even one lap.

https://github.com/ruby/ruby/blob/trunk/range.c#L833

static VALUE
range_each(VALUE range)
{
//...abridgement
	    if (!NIL_P(end))
		range_each_func(range, each_i, 0);
	    else
		for (;; beg = rb_funcallv(beg, id_succ, 0, 0))
		    rb_yield(beg);
//...abridgement
}

https://github.com/ruby/ruby/blob/trunk/range.c#L239

static void
range_each_func(VALUE range, int (*func)(VALUE, VALUE), VALUE arg)
{
    int c;
    VALUE b = RANGE_BEG(range);
    VALUE e = RANGE_END(range);
    VALUE v = b;

    if (EXCL(range)) {
	while (r_less(v, e) < 0) {
	    if ((*func)(v, arg)) break;
	    v = rb_funcallv(v, id_succ, 0, 0);
	}
    }
    else {
	while ((c = r_less(v, e)) <= 0) {
	    if ((*func)(v, arg)) break;
	    if (!c) break;
	    v = rb_funcallv(v, id_succ, 0, 0);
	}
    }
}

https://github.com/ruby/ruby/blob/trunk/range.c#L157

/* compares _a_ and _b_ and returns:
 * < 0: a < b
 * = 0: a = b
 * > 0: a > b or non-comparable
 */
static int
r_less(VALUE a, VALUE b)
{
    VALUE r = rb_funcall(a, id_cmp, 1, b);

    if (NIL_P(r))
	return INT_MAX;
    return rb_cmpint(r, a, b);
}