From: Thomas Sawyer <transfire@...>
Date: 2012-02-14T05:54:36+09:00
Subject: [ruby-core:42573] [ruby-trunk - Feature #4890] Enumerable#lazy


Issue #4890 has been updated by Thomas Sawyer.


@Rodrigo I'm not suggesting Enumerable methods be lazy. I asking about Enumerator methods being lazy. So first you have to convert to an Enumerator.

  items.to_enum.map{ ... }

As it happens, enumerable methods without a block become enumerators, so

  items.each.map{ ... }

Would be the same.

Just calling `items.map` would not be any different then it is now.

----------------------------------------
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

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

=end



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