Completes an array with missing consecutive numbers. Kind of a linear interpolation. Read something more here http://stackoverflow.com/questions/4570755/calculate-missing-values-in-an-array-from-adjacent-values

interpolation.rb

list = [2, 3, 4, 6, 7, 9, 12]
[].tap{ |array|
  [0, *list, 0].each_cons(3).map do |p, x, n|
    array << x;
    (n - x).times{|i| array << x + i if i > 0}
  end
} # => [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]