From: Michael Judge <mjudge@...>
Date: 2007-06-26T05:53:35+09:00
Subject: .include?/.within? and English-thinking brains

In English, it's clearer to ask, "Is Maggie one of the guests?" --  
rather than the awkward, "Does the guests include Maggie?"

So why in Ruby, do we write, "list.include? scalar" -- when we often  
mean, "scalar.within? list" ?!

The solution:

   module Comparable
     def within?(list)
       list.include? self
     end
   end

   #
   # Examples:
   #

   1.within? [1,2,3]
   # => true

   1.within? [2,3]
   # => false

   "arr".within? "arr, matey"
   # => true

   "arr".within? "monkey patch"
   # => false

   1.within?( 1 => "value" )
   # => true

   1.within?( 2 => "value" )
   # => false

   1.within? 1..3
   # => true

   1.within? 2..3
   # => false

Try it for a morning, your brain will feel better.