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Validate An Odd Or Even Number In Ruby

03.24.2010
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x%2 == 0 ? true : false

x = 5
x%2 == 0 ? true : false
#=> false

x = 8
x%2 == 0 ? true : false
#=> true
or
Fixnum.class_eval { def even?; self%2 == 0 ? true : false; end }
133.even? #=> false
144.even? #=> true

Resources:
 - <a href="http://snippets.dzone.com/posts/show/2677">test for even and odd numbers</a> [dzone.com]
 - <a href="http://bmorearty.wordpress.com/2009/01/09/fun-with-rubys-instance_eval-and-class_eval/">Fun with Ruby’s instance_eval and class_eval « I like stuff.</a> [wordpress.com]

*update: 24-Mar-2010 @11:45am*

I've realised the condition can be shortened to x%2 == 0 e.g.
Fixnum.class_eval { def even?; self%2 == 0; end }
133.even? #=> false
144.even? #=> true