Feature #8506

Updated by Nobuyoshi Nakada over 1 year ago

=begin
Ruby's (({Enumerator})) `Enumerator` and (({#enum_for})) `#enum_for` methods are very powerful and I use them very often. However, (({Object#enum_for})) `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.})) `Fixnum#next.` There is no way to use (({Fixnum#next})) `Fixnum#next` with (({#enum_for})) `#enum_for` directly that I am aware of.

I propose the introduction of (({Object#iter_for})) `Object#iter_for` which--given a method--generates a lazy sequence by continually invoking the method on successive values. I call it (({iter})) `iter` or (({iterate})) `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)})) `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 `Enumerator.new { |y| i = 0; loop { y << i; i += 1 } }})) }` or (({(0..Float::INFINITY).each})). `(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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