ツナでもわかるmruby [5回目：配列と遅延評価] ref: http://qiita.com/hiroeorz@github/items/371a12316091c63a3aa8

array-time-lazy.rb

start_time = Time.now
Array.new(1000000, 1).lazy.map{|e| e}.take(3).force
end_time = Time.now

process_time = end_time - start_time
puts "process time: #{process_time}"

array-time.rb

start_time = Time.now
Array.new(1000000, 1).map{|e| e}[0, 3]
end_time = Time.now

process_time = end_time - start_time
puts "process time: #{process_time}"

mirb

[1,2,3,4,5,6,7,8,9,10].lazy.map{|e| e * e}.
                       select{|e| (e % 2) == 0}.
                       take(3).
                       force

mruby1.0.0

$ mruby array-time-lazy.rb 
process time: 0.17267199999999

ruby2.1.1

$ ruby array-time-lazy.rb 
process time: 0.00678566