Remove adjacent identical elements in a Ruby Array?

Question

Ruby 1.8.6

I have an array containing numerical values. I want to reduce it such that sequences of the same value are reduced to a single instance of that value.

Answer 1

For the simplest, leanest solution, you could use the method Enumerable#chunk:

a.chunk(&:itself).map(&:first)

The itself method is Ruby 2.2+. Use {|n| n} if you are stuck in an older Ruby, or my backports gems. It was introduced in Ruby 1.9.2. If you're unlucky enough to be using older rubies, you could use my backports gem and require 'backports/1.9.2/enumerable/chunk'.