Feature #8506

Object#iter_for / Object#to_iter

Added by alindeman (Andy Lindeman) almost 4 years ago. Updated almost 4 years ago.

Target version:


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:

Proposed API:

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

require 'date', 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: (({ { |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.


#2 [ruby-core:55390] Updated by Anonymous almost 4 years ago

Btw., regarding Qbject#to_enum, what is your opinion? Do you use it often? Or is there something about it that makes it less useful?

#3 [ruby-core:55398] Updated by nobu (Nobuyoshi Nakada) almost 4 years ago

  • Description updated (diff)

You may want to show the implementation in ruby (and tests)?

#5 [ruby-core:55403] Updated by phluid61 (Matthew Kerwin) almost 4 years ago

nobu (Nobuyoshi Nakada) wrote:

You may want to show the implementation in ruby (and tests)?

Here is an implementation:

Also available in: Atom PDF