Check that a Range covers an element in both Ruby 1.9 and 1.8.7

In order to cover some edge cases you rarely care about, Range#include? will become very slow in Ruby 1.9 Show archive.org snapshot :

Range#include? behaviour has changed in ruby 1.9 for non-numeric ranges. Rather than a greater-than/less-than check against the min and max values, the range is iterated over from min until the test value is found (or max) [...] Ruby 1.9 introduces a new method Range#cover? that implements the old include? behaviour, however this method isn’t available in 1.8.7.

The attached code will add a Range#cover? method to your Ruby 1.8.7 and not do anything in Ruby 1.9+. This way you can always use cover? now and don't need to change your code when you switch to Ruby 1.9.