From: cabeer@...
Date: 2015-12-12T17:45:11+00:00
Subject: [ruby-core:72083] [Ruby trunk - Bug #11811] [Open] Chaining lazy enumerators causes duplicate ouput

Issue #11811 has been reported by Chris Beer.

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Bug #11811: Chaining lazy enumerators causes duplicate ouput
https://bugs.ruby-lang.org/issues/11811

* Author: Chris Beer
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: ruby 2.3.0preview2 (2015-12-11 trunk 53028) [x86_64-darwin15]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
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In Ruby 2.3.0-preview2, I'm seeing a change in behavior using lazy enumerators with select/reject and the & operator:

irb(main):037:0> %w(1 2 3).lazy.reject(&:empty?).each { |x| puts x }
1
1
2
2
3
3

Note that the output is doubled. However, if I don't use the & shorthand, the output is as expected:


irb(main):038:0> %w(1 2 3).lazy.reject { |x| x.empty? }.each { |x| puts x }
1
2
3
=> nil


And in Ruby 2.2.3, both variants produced the same result:

irb(main):001:0> %w(1 2 3).lazy.reject(&:empty?).each { |x| puts x }
1
2
3
=> nil




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