From: "boris_stitnicky (Boris Stitnicky)" <boris@...>
Date: 2013-06-10T00:38:32+09:00
Subject: [ruby-core:55390] [ruby-trunk - Feature #8506] Object#iter_for / Object#to_iter


Issue #8506 has been updated by boris_stitnicky (Boris Stitnicky).


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?
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Feature #8506: Object#iter_for / Object#to_iter
https://bugs.ruby-lang.org/issues/8506#change-39816

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


-- 
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