What's the easiest way to create a repeating sequence a la: ['a','b'][2]='a'

I fi开发者_StackOverflow中文版nd myself wondering if there's a built-in Ruby method to get the nth number in a 12-element sequence, no matter how large 'n' is.

For example, if I have a sequence (portrayed as an array below) that has 3 elements, and if I try to access the fourth element, it starts from the beginning. Here's a method that will do this, but I wonder if there's a built-in way to do it.

Array.class_eval do
  def sequenced(n)
    n/size >= 1 ? fetch(n%size) : fetch(n)
  end
end

['a', 'b', 'c'].sequenced(3) => 'a'

Why do you need to special case the n < size case? Just use fetch(n%size)

In Ruby 1.9:

['a', 'b', 'c'].cycle.take(size).last