# Where is Enumerable#each\_cons()?

**URL:** <https://www.ruby-forum.com/t/where-is-enumerable-each-cons/113799>\
**Category:** Ruby\
**Created:** [September 5, 2007, 3:47am UTC](https://www.ruby-forum.com/t/where-is-enumerable-each-cons/113799 "2007-09-05T03:47:06Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [September 5, 2007, 3:47am UTC](https://www.ruby-forum.com/t/where-is-enumerable-each-cons/113799/1 "2007-09-05T03:47:06Z")

</div>

Using: ruby 1.8.6 (2007-03-13 patchlevel 0) [i386-mswin32]  
and: ruby 1.8.4 (2006-02-24) [x86\_64-linux]

I can’t find Enumerable#each\_cons in either version – always a  
NoMethodError:

irb(main):001:0\> [1, 2, 3].cons(2) {|a| p a}  
=\> NoMethodError: undefined method `cons’ for [1, 2, 3]:Array from  
(irb):1

irb(main):002:0\> (1…10).each\_cons(2) {|a| p a}  
=\> NoMethodError: undefined method `each\_cons’ for 1…10:Range from  
(irb):2

Am I missing something? (Besides #each\_cons, of course.)

Jeremy

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<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [September 5, 2007, 4:10am UTC](https://www.ruby-forum.com/t/where-is-enumerable-each-cons/113799/2 "2007-09-05T04:10:09Z")

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Try requiring enumerator.

irb(main):001:0\> require “enumerator”  
=\> true  
irb(main):002:0\> (1…10).each\_cons(2) {|a| p a}  
[1, 2]  
[2, 3]  
[3, 4]  
[4, 5]  
[5, 6]  
[6, 7]  
[7, 8]  
[8, 9]  
[9, 10]  
=\> nil