From: Joshua Ballanco Date: 2012-02-14T04:50:52+09:00 Subject: [ruby-core:42567] [ruby-trunk - Feature #4890] Enumerable#lazy Issue #4890 has been updated by Joshua Ballanco. I think the main difference is that current Enumerable#{map|select|inject} use yield semantics with the block. This is not always conducive to lazy evaluation: class AlwaysThree include Enumerable def each yield 3 end end AlwaysThree.new.each { |i| puts i } #=> 3 AlwaysThree.new.map { |i| i**2 } #=> [9] I realize that's a trivial example, but I think lazy enumerables will require generator semantics. i.e. Instead of everything being based around #each, it should be based around #next. ---------------------------------------- Feature #4890: Enumerable#lazy https://bugs.ruby-lang.org/issues/4890 Author: Yutaka HARA Status: Assigned Priority: Normal Assignee: Yutaka HARA Category: core Target version: 2.0.0 =begin = Example Print first 100 primes which are in form of n^2+1 require 'prime' INFINITY = 1.0 / 0 p (1..INFINITY).lazy.map{|n| n**2+1}.select{|m| m.prime?}.take(100) (Example taken from enumerable_lz; thanks @antimon2) = Description Enumerable#lazy returns an instance of Enumerable::Lazy. This is the only method added to the existing bulit-in classes. Lazy is a subclass of Enumerator, which includes Enumerable. So you can call any methods of Enumerable on Lazy, except methods like map, select, etc. are redefined as 'lazy' versions. = Sample implementation (()) (also attached to this ticket) =end -- http://bugs.ruby-lang.org/