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List:       ruby-core
Subject:    [ruby-core:44771] [ruby-trunk - Feature #6367] #same? for Enumerable
From:       "pabloh (Pablo Herrero)" <pablodherrero () gmail ! com>
Date:       2012-04-30 14:35:43
Message-ID: redmine.journal-26335.20120430233542 () ruby-lang ! org
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Issue #6367 has been updated by pabloh (Pablo Herrero).


#same_elements?

or

#same_members?
----------------------------------------
Feature #6367: #same? for Enumerable
https://bugs.ruby-lang.org/issues/6367#change-26335

Author: prijutme4ty (Ilya Vorontsov)
Status: Feedback
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: 
Target version: 


I realised that I frequently test if all objects in enumerable have the same feature. \
For example if all words have the same length (but not defined before). So I found \
particulary useful method Enumerable#same_by? that test this behaviour. I think it \
can be simply rewritten in C and included to Enumerable core methods. Simple ruby \
implementation can be written just in a pair of lines (tests included):

module Enumerable
  def same?(&block)
    return true if empty?
    if block_given?
      first_result = yield(first)
      all?{|el| first_result == yield(el)}
    else
      first_result = first
      all?{|el| first_result == el}
    end
  end
end

require 'test/unit'
class TestEnumerableSame < Test::Unit::TestCase
  def test_same
    assert_equal(true, [1,3,9,7].same?(&:even?))
    assert_equal(true, [4,8,2,2].same?(&:even?))
    assert_equal(false, [1,8,3,2].same?(&:even?))
    
    assert_equal(true, %w{cat dog rat}.same?(&:length))
    assert_equal(false, %w{cat dog rabbit}.same?(&:length))
    
    assert_equal(true, %w{cat cat cat}.same?)
    assert_equal(false, %w{cat dog rat}.same?)
    
    assert_equal(true, [].same?(&:length))
    assert_equal(true, [].same?)
  end
end



-- 
http://bugs.ruby-lang.org/


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