Issue #4890 has been updated by Alexey Muranov.


Rodrigo Rosenfeld Rosas wrote:
> Thomas, I think it only makes sense for enumerables to be lazy if you call take(n) on it.
> 
> Usually, you want all elements when calling any of those methods without explicitly marking them as lazy.

I disagree, i think lazy versions of all methods that return arrays are useful, to avoid generating intermediate arrays and to be able to work with infinite collections.

Alexey.
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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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