[ruby-core:114895] [Ruby master Feature#13933] Add Range#empty? - ruby-core - ml.ruby-lang.org

24 Sep 2023

Issue #13933 has been updated by Dan0042 (Daniel DeLorme).

akr (Akira Tanaka) wrote in #note-12:
...
  From experience with `Float::NAN`, I think it is not a
good idea to expand such objects.
 It makes the behavior of `Array#<=>` inconsistent. 
I agree but I think this is a bit different from what I was talking about. Float::NAN is a
float that is not comparable with other floats. This is not the same case as a value that
is not comparable with anything else.

...
  There is no reason to break it. 
I agree; as I said, I'm not suggesting we change this now.

...
   Or maybe we
can define a range "r" as empty if `r.begin.nil? and r.exclude_end? and
r.end.respond_to?(:empty?) and r.end.empty?`  
 You ignored the user-defined classes I mentioned.
 A user may define a class with a minimum value.
 The minimum value may not have `empty?` method. 
How do you define which is the minimum value? I suggested the above as a *posssible* way
to define the minimum value. So a custom class would need to have #empty? that returns
true in order to define "this is the minimum". But it was just a suggestion. Or
maybe each class could have a MINIMUM constant like `String::MINIMUM = ""`, etc.
More importantly, I think that `(...minimum).empty?` is such an edge case of an edge case
that it's not worth worrying too much. Are you suggesting that `Range#empty?` should
not exist just because it's not possible to perfectly handle this extreme edge case
for every possible class? Would it really be so bad if it returned `true` for user-defined
classes?

----------------------------------------
Feature #13933: Add Range#empty?
https://bugs.ruby-lang.org/issues/13933#change-104753

* Author: ted (Ted Johansson)
* Status: Open
* Priority: Normal
----------------------------------------
Range already responds to #size. It would be nice if it also responded to predicate
#empty? :-)

-- 
https://bugs.ruby-lang.org/