From: Suraj Kurapati <sunaku@...>
Date: 2011-07-27T03:21:37+09:00
Subject: [ruby-core:38528] [Ruby 1.9 - Feature #4589] add Queue#each() method and include Enumerable


Issue #4589 has been updated by Suraj Kurapati.


Perhaps this code example can better illustrate my request:

class Queue
  def each(&block)
    temporary_copy = @internal_queue_lock.synchronize do
      @internal_item_array.dup
    end
    temporary_copy.each(&block)
  end
end

Charles Nutter wrote:
> At first I thought this would be a good idea. But then I realized
> that #each is, in every case I can think of, a non-mutating
> operation.

Yes, that was my intention: read-only iteration of the queue.

> Since I assume you meant for Queue#each to pop all elements off
> the queue, this would be the first example I know of a mutating
> #each.

Sorry if my request was unclear, but that is not what I requested.

> Also, what happens when the queue is empty? Does it wait for
> another element, or does it end the iteration?

It should be non-blocking.  Simply iterate over the items that are
currently in the queue.

If the method was blocking, it would never finish, because we would
never reach the "end" of the queue.

> The behavior of #each over a queue seems fuzzy to me, and without
> a clear specification of what you want I don't see a path forward.

I hope my responses above clarify this feature request.


Eric Hodel wrote:
> I don't think it is appropriate to include Enumerable.  Too many
> methods from Enumerable seem inappropriate (or behavior would be
> application-specific).  For example, should #find block, or only
> return items that match in the Queue?

Since Enumerable relies on #each(), and the Queue#each method I'm
requesting is non-blocking, all of the non-destructive Enumerable
methods (like #find, #select, #map) should work as we normally
expect them to.

> Should #reject remove items from the Queue, or only filter?

#reject should filter (read-only).  #reject! should remove items.

> I can see differing needs depending on if the Queue has a single
> consumer or multiple consumers.

Hmm, shouldn't the thread-safe aspect of Queue take care of that?

----------------------------------------
Feature #4589: add Queue#each() method and include Enumerable
http://redmine.ruby-lang.org/issues/4589

Author: Suraj Kurapati
Status: Open
Priority: Normal
Assignee: 
Category: lib
Target version: 


=begin
Please add a thread-safe each() method to the Queue and SizedQueue classes
which are provided by the "thread" standard library

Also mix-in the Enumerable module into those classes so we can use map/inject/etc.

Thanks for your consideration.
=end



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