From: "headius (Charles Nutter)" <headius@...>
Date: 2013-06-24T03:51:28+09:00
Subject: [ruby-core:55612] [ruby-trunk - Feature #6373] public #self


Issue #6373 has been updated by headius (Charles Nutter).


phluid61 (Matthew Kerwin) wrote:
> laise (Alexey Chernenkov) wrote:
> > It is a VERY usefull feature! Can't understand why #tap still need to be used with block only.
> 
> Because it's called "tap."  Tap doesn't "return self", it taps into an execution flow, extracting an intermediate value for inspection without interrupting the original flow.  The analogy is literally tapping a hole in a pipe, to extract liquid samples at various phases in a process.  (Also think of tapping a phone line.)  Changing its semantics to a straight-up "returns self" method would just make it idiosyncratic, instead of metaphoric.

I still like #tap.

1. It would only require removal of the block-yielding requirement.
2. It's functionally equivalent to tapping into execution flow but doing nothing, as in tap {}. I think the objection that it no longer means we're tapping execution flow is a bit pedantic; we *are* tapping execution flow, but the only operation we seek is the reference to the object.

My favorite remains #self, but I can appreciate objections, especially confusion over "self" and "obj.self" and especially "self.self" if #self can be overridden. It does have the advantage that there's probably fewer libraries that define their own "self" method than any other suggestion here.

Other systems I know would use #identity. It also maps to functional programming language for a function that just returns its sole argument (in this case, the 0th argument, the object itself). I would support #identity as well.

> Matz wrote:
> > The point is when we see the code like:
> >
> >   [1,2,3,4,5,1,2,2,3].group_by(&:self)
> >
> > sometimes it would be less intuitive that self refers elements in the array, not self in the scope.
> 
> I have trouble imagining such a scenario.  I actually think the `some_array.group_by(&:self)` example is a strong plus for this feature.
> 
> I'm also not entirely convinced it's really YAM, since 'self' is already a word in the language, all we're doing is pushing it from keyword to keyword+method, i.e. making it more easily accessible from outside the instance.  Even more so since this use-case is really the only place it will ever show up; if there was another way to to_proc the 'self' keyword to make it easy to pass to a method like group_by I'd be for that as well/instead.

Another option based on matz's objection: #reference. We want a method that returns the reference to the object we're calling against. #reference seems logical.

[1,2,3,4,5,1,2,2,3].group_by(&:reference)

Variations on this might be #self_reference, #self_ref, #selfref. Also #self_object, #self_obj, #selfobj.

#self and #identity are probably the most likely to be guessed by a new user.
----------------------------------------
Feature #6373: public #self
https://bugs.ruby-lang.org/issues/6373#change-40101

Author: trans (SYSTEM ERROR)
Status: Feedback
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: next minor


=begin
This was recently suggested to me as an extension:

  class Object
    # An identity method that provides access to an object's 'self'.
    #
    # Example:
    #   [1,2,3,4,5,1,2,2,3].group_by(&:identity)
    #   #=> {1=>[1, 1], 2=>[2, 2, 2], 3=>[3, 3], 4=>[4], 5=>[5]}
    #
    def identity
      self
    end
  end

First, is such a method commonly useful enough to warrant existence?

Second, it makes me wonder if #self should be a public method in general.
=end


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