From: Shugo Maeda <redmine@...>
Date: 2011-11-01T11:57:02+09:00
Subject: [ruby-core:40596] [ruby-trunk - Feature #4890] Enumerable#lazy


Issue #4890 has been updated by Shugo Maeda.


One more question.

Shugo Maeda wrote:
> Akinori MUSHA wrote:
> > My suggestion is to turn Enumerator into a lazy stream and make every Enumerable class including the new Enumerator operate on the receiver's class wherever appropriate instead of fixing Array as result container.
> 
> It sounds fine for me, but I don't think Enumerable (or Enumerator) should have methods of Array such as [] and size.

How about to add Enumerable#defer that returns a lazy version of Enumerator as a transition step in Ruby 2.0?
If Enumerator gets lazy in Ruby 3.0, Enumerable#defer can be changed to be just an alias of to_enum.

----------------------------------------
Feature #4890: Enumerable#lazy
http://redmine.ruby-lang.org/issues/4890

Author: Yutaka HARA
Status: Open
Priority: Normal
Assignee: Yukihiro Matsumoto
Category: core
Target version: 3.0


=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

((<URL:https://gist.github.com/1028609>))
(also attached to this ticket)

=end



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