From: David Masover <ninja@...>
Date: 2010-03-25T13:03:25+09:00
Subject: Re: How to create an infinite enumerable of Times?

On Wednesday 24 March 2010 10:35:16 pm Alex Baranosky wrote:
> infinite list of Mondays (for example).
> 
> So it would yield: March 29, April 5, April 12...... etc
> 
> How can I implement this in Ruby?

First learn to implement Enumerable, then it should be obvious. All you need 
to do is define a #each method. So, for example, here's an implementation of 
all numbers:

class PositiveIntegers
  include Enumerable
  def each
    i = 1
    while true
      yield i
      i += 1
    end
  end
end

If you can figure out how to do a similar loop for Mondays, you can do that.

Keep in mind that this kind of thing isn't nearly as cool in practice as you 
might like -- for one, a lot of the reasons you'd want an enumerable are not 
going to work well. For example, calling .map{...}.each is probably going to 
result in an infinite loop, as map returns an array.

I would probably do it like this:

module Foo
  def self.positive_integers
    return enum_for(:positive_integers) unless block_given?
    i = 1
    while true
      yield i
      i += 1
    end
  end
end

So that means you could do this:

Foo.positive_integers { ... }

Or, that enum_for means you could also do this:

Foo.positive_integers.each { ... }