From: Christopher Dicely <cmdicely@...>
Date: 2010-08-28T14:43:03+09:00
Subject: Re: how about Array#collect_until

On Fri, Aug 27, 2010 at 9:40 PM, timr <timrandg@gmail.com> wrote:

> The other tests may help clarify the expected behavior. In each case
> the method should result in a collection that DOES NOT INCLUDE A
> RESULT FOR EVERY ITEM in the original set since the condition is met
> part way through and break is executed. Therefore, it provides the
> most a collection of calculations upto and including the solution when
> an end condition was met.

Okay.. I misunderstood the intent. So you can't use the
Enumerable#through method I proposed upthread quite as simply, because
you have to reverse the order of the filtering and transforming
operations, and the existing transforming operation for enumerables
(Enumerable#map) produces an array, not an Enumerator, and
Kernel#enum_for won't pass a block to map (or any other method) to
create an Enumerator that uses the block.

But its easy to create a general-purpose map-like enumerator method.

module Enumerable
  def transform
    Enumerator.new do |yielder|
      self.each { |val| yielder << yield(val) }
    end
  end
end

Then you can just chain this Enumerable#transform in front of the
Enumerable#through I proposed upthread,