Question

Is there a gem or a library to get ruby 1.9 methods like

[1, 2, 3].combination(2)
[1, 2, 3].permutation(2)
[1, 2, 3].product([1, 2, 3])
[1, 2, 3, 4, 5].cycle

Answer 1

This is exactly the goal of my gem backports.

It implements in pure Ruby all the new features of Ruby 1.8.7 and many of Ruby 1.9.x and 2.0. This of course includes #combination, #permutation, #product and #cycle.

You can, for example:

require 'backports/1.8.7/array/combination'
[1, 2, 3].combination(2) # => works, even in Ruby 1.8.6

The implementation in backports pass most RubySpecs (which is not the case for facets) to guarantee not having compatibility problems.