Some extensions to Ruby's Enumerable class to allow some fancy functional programming. More info here: http://ukoki.com/post/38615453403/extending-rubys-enumerable

enumerable_functional_extensions.rb

#
# Extensions to Enumerable to add more functional operators
# More info here: http://ukoki.com/post/38615453403/extending-rubys-enumerable
#

module Enumerable

  # example:
  # [1,2,3].zip_map([1,2,3], [1,2,3]) { |x,y,z| x * y * z }
  # => [1,8,27]
  def zip_map *lists
    self.map.with_index do |elem, idx| 
      args = [elem] + lists.each.with_object(idx).map(&:[])
      yield *args, idx
    end
  end

  # example:
  # [[1,2],[3,4],[5,6]].map_at_level(2) { |n| -n }
  # => [[-1, -2], [-3, -4], [-5, -6]] 
  def map_at_level level = 1, &block
    if level <= 1
      self.map &block
    else
      self.map { |e| e.map_at_level level-1, &block }
    end
  end

  # example:
  # [[1,2,3],['a','b','c']].transpose
  # => [[1, "a"], [2, "b"], [3, "c"]]
  def transpose
    self.with_index do |i| 
      yield self.with_object(i).map &:[]
    end
  end

  # example:
  # [[[[1],[2],[3]],[['a'],['b'],['c']]]].flatten_at_level(2)
  # => [[[1, 2, 3], ['a','b','c']]]
  def flatten_at_level level, depth = nil
    self.map_at_level(level) { |list| list.flatten depth }
  end

  # example:
  # [1,2,3,4,5,6,7,8,9,10].group(3)
  # => [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
  def group size # groups list into sublists of size 'size'
    self.each_slice(size).to_a
  end

  def blockify width, height = nil # groups 2D array into sub-2D-arrays of size widthxheight
    self.each_slice(height||width).map { |n| n.transpose.group(width) }.flatten(1)
  end
end

I find sometimes useful

module Enumerable
  # Maybe somedays: .each(&:method, args) do; end 
  def each_call(method, *args,  &block) = each { _1.send method, *args, &block }
  def map_call(method, *args,  &block) = map { _1.send method, *args, &block }
  def map_call!(method, *args,  &block) = map! { _1.send method, *args, &block }
end
# ======
a = %w[a b c]
a.each_call(:instance_eval) do
    @var = 1
end
p a.map_call(:+, '!')