Issue #14701 has been updated by sonots (Naotoshi Seo).


As first thing to say, we do not expect changing behavior of `+=` for ruby built-in types such as string or array.

We want to have an extension point to redefine `+=` for our library such as NArray.
How it should behave is the design choice and responsibility of such libraries.

> Most Rubyists know and expect that Array#+ is non-destructive, so I think that it is unacceptable to allow this.

I mean that It is even possible to redefine `+` operator to be destructive. It is design choice and responsibility of libraries.

> Do you mean introducing another set of destructive operators, like a +! 1 instead of a += 1? It is not very cool, but it seems more reasonable to me.

Yes, as a compromise. I still prefer `+=`, though.

> IMO, the fundamental flaw is to split + and +=.

IMO, it is design responsibility of libraries. But, I understand what you says partially. I will think of this.

----------------------------------------
Feature #14701: If the object is not frozen, I want to be able to redefine the compound assignment operator.
https://bugs.ruby-lang.org/issues/14701#change-71652

* Author: naitoh (Jun NAITOH)
* Status: Rejected
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
If the object is not frozen, I want to be able to redefine the compound assignment operator (e.g. +=, -=, *=, /=, ..etc ).

https://docs.ruby-lang.org/ja/latest/doc/spec=2foperator.html

* Redefinable operator (method) 

~~~
    |  ^  &  <=>  ==  ===  =~  >   >=  <   <=   <<  >>
    +  -  *  /    %   **   ~   +@  -@  []  []=  ` ! != !~
~~~

* use case

~~~
> require 'numo/narray'
> a = Numo::Int32[5, 6]
=> Numo::Int32#shape=[2]
[5, 6]
> a.object_id
=> 70326927544920
> a += 1
=> Numo::Int32#shape=[2]
[6, 7]
> a.object_id
=> 70326927530540
> a.inplace + 1
=> Numo::Int32(view)#shape=[2]
[7, 8]
> a.object_id
=> 70326927530540
~~~

With Numo::NArray, using "inplace" instead of "+=" will update the same object so it will be faster.

I want to write "a += 1" instead of "a.inplace + 1".
However, Ruby can not redefine "+=".



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