From: Roger Pack <rogerpack2005@...>
Date: 2009-11-14T03:45:00+09:00
Subject: Re: RCR enumerable extra into core

>This reminds me of the early 1.9.0 thing, where you could do:
>
>    array = [1,2,3,4]
>    enum = array.enum_for(:map, &lambda {|x| x * x })
> 
>    enum.next   # 1
>    enum.next   # 4


Appears somewhat possible...

class Enumerator
  def filter(&blk)
    self.class.new do |y|
      each do |*input|
        out = blk.call(*input)
        y << out
        # or y << out if out
      end
    end
  end
end

>> array = [1,2,3,4]
>> enum = array.enum_for(:map).filter {|x| x * x }
>> enum.next
=> 1
>> enum.next
=> 4

>> enum.select {|x| x > 1 } # [4, 9, 16]
=> [4, 9, 16]

[Thanks to Brian Candler for the snippet--though perhaps it could be 
improved...]

This should be the default, though--I don't know why blocks are ignored 
currently...

-r

http://www.ruby-forum.com/topic/169844#new
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