From: "ko1 (Koichi Sasada)" <redmine@...>
Date: 2013-08-07T09:53:43+09:00
Subject: [ruby-core:56421] [ruby-trunk - Feature #8639] Add Queue#each


Issue #8639 has been updated by ko1 (Koichi Sasada).


# Please assume
#  @q_buf is current buffer (array) of queue in following example.
#  @q_lock is lock of this Queue.

People think Queue#each should be:

(1) Infinite loop

  # iterate forever
  def each
    loop{
      yield @q_buf.shift
    }
  end

(2) Finite loop

(2-1) Mutable behavior

  # iterate untile elements are exists
  def each
    loop{
      e = nil
      @q_lock.lock{
        return if @q_buf.empty?
        @q_buf.shift
      }
      yield e
    }
  end

(2-2) Immutable behaviour

  def each(&b)
    @q_buf.dup.each(&b)
  end
  # only for chekcking current elements
  # not for inter-thraed communication

# Please add another possible version.


Your proposal is (1). (1) is shorter version of

  while e = q.pop
    break if e == :end
    ...
  end

which I wrote frequently.

  q.each{|e|
    break if e == :end
    ...
  }



I'm weak negative because
  (a) seems not so convinient
  (b) #each method is for Enumerable
      If we find #each method, then we think it is Enumerable.
  (c) we have only few cases for infinite iteration #each methods.
  (d) I can think 3 versions described above with in seconds.


BTW, I think your `non-blocking' parameter should be a switch of (1) and (2-1).



----------------------------------------
Feature #8639: Add Queue#each
https://bugs.ruby-lang.org/issues/8639#change-40951

Author: avdi (Avdi Grimm)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 


I was fiddling around with Queue the other day and realized it doesn't have an #each method. So I made one: https://github.com/ruby/ruby/pull/361

As for why, it makes for a convenient way to build consumer processes:

  inq = Queue.new
  outq = Queue.new
  doubler = Thread.new do
    inq.each do |n|
      outq << n + n
    end
  end

My PR also returns an Enumerator when no block is given, and handles the non_block argument.

I'm sure there's some good reason that this method wasn't there already, so feel free to explain.

Also, this is my first Ruby feature ticket so please let me know if I'm missing any points of protocol.

Thanks!


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