http://ruby-doc.org/core-2.0/Enumerable.html#method-i-inject[1, 2, 3, 4].inject(0) { |result, element| result + element } # => 10ary = %w(1 2 2 3 3 3 4 4 4 4) ary.inject(Hash.new(0)){|hash, a| hash[a] += 1; hash} #=> {"1"=>1, "2"=>2, "3"=>…