From: "avdi (Avdi Grimm)" <avdi@...>
Date: 2013-07-16T09:10:32+09:00
Subject: [ruby-core:56032] [ruby-trunk - Bug #8641][Open] Enumerator size argument is either mis-documented or should accept any callable


Issue #8641 has been reported by avdi (Avdi Grimm).

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Bug #8641: Enumerator size argument is either mis-documented or should accept any callable
https://bugs.ruby-lang.org/issues/8641

Author: avdi (Avdi Grimm)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: ruby 2.0.0p0 (2013-02-24 revision 39474) [x86_64-linux]
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


I ran into this while wrapping Enumerators around Queues. The Enumerator docs state:

  * The optional parameter can be used to specify how to calculate the size
  * in a lazy fashion (see Enumerator#size). It can either be a value or
  * a callable object.

However:

  require 'thread'
  q = Queue.new
  eq = Enumerator.new(q.method(:size)) do |y|
    loop do
      y << q.pop
    end
  end
  eq.size # => 
  # ~> -:3:in `initialize': no implicit conversion of Method into Integer (TypeError)
  # ~> 	from -:3:in `new'
  # ~> 	from -:3:in `<main>'

It looks like the size can't be any callable; it must be Proc a or an Integer. The code uses rb_obj_is_proc().

Instinctively I'd say that the documentation has it right and it ought to take any callable. But if there's some reason it's limited to Procs, the docs should be changed.

If anyone can point me in the right direction I'm happy to do the legwork on this.


-- 
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