From: "Eregon (Benoit Daloze)" <redmine@...>
Date: 2013-06-10T17:20:01+09:00
Subject: [ruby-core:55402] [ruby-trunk - Feature #8506] Object#iter_for / Object#to_iter


Issue #8506 has been updated by Eregon (Benoit Daloze).


Here is the related blogpost: http://alindeman.github.io/2013/06/10/porting-iterate-to-ruby.html
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Feature #8506: Object#iter_for / Object#to_iter
https://bugs.ruby-lang.org/issues/8506#change-39827

Author: alindeman (Andy Lindeman)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 


=begin
Ruby's (({Enumerator})) and (({#enum_for})) methods are very powerful and I use them very often. However, (({Object#enum_for})) requires a method that yields, usually in some sort of loop.

Many objects in Ruby have methods that iterate to a "next value," but do not yield. For example, (({Fixnum#next.})) There is no way to use (({Fixnum#next})) with (({#enum_for})) directly that I am aware of.

I propose the introduction of (({Object#iter_for})) which--given a method--generates a lazy sequence by continually invoking the method on successive values. I call it (({iter})) or (({iterate})) because it is very similar to clojure's iterate: http://clojure.github.io/clojure/clojure.core-api.html#clojure.core/iterate

Proposed API:

  0.iter_for(:next).take(5) # => [0, 1, 2, 3, 4]

  require 'date'
  Date.new(2013, 1, 1).iter_for(:next_month).take(3) # => [Tue, 01 Jan 2013, Fri, 01 Feb 2013, Fri, 01 Mar 2013]

I am especially excited about (({0.iter_for(:next)})) as I find myself using infinite lazy numeric sequences more often lately to solve specific kinds of problems. Right now you are required to write something like: (({Enumerator.new { |y| i = 0; loop { y << i; i += 1 } }})) or (({(0..Float::INFINITY).each})). Neither is especially elegant or happy to the developers' eyes in my opinion.

Thank you all :) Ruby is an amazing tool.
=end



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