From: Ara.T.Howard@...
Date: 2004-09-21T03:14:39+09:00
Subject: Re: Array#index block and rdetect

On Tue, 21 Sep 2004, trans.  (T. Onoma) wrote:

> One begins to wonder if maybe blocks might have "underwritten" parameters. Not
> sure how it might work, but basically there would be special global
> variables.  Pseudo-example:
>
>  ["A", "B", "C"].each {|e| p [e, $count, $begin, $end] }
>
>  ["A", 0, 0, 2]
>  ["B", 1, 0, 2]
>  ["C", 2, 0, 2]

good idea but evil impl! ;-)  perhaps a block iterator proxy object:

   class BlockIteratorProxy

     %w(
       count
       begin
       end
       proxy
     ).each{|a| attr a, true}

     def intialize proxy
       @proxy = nil
     end

     def method_missing(*a,&b);proxy.send(*a,&b);end
   end

eg. usage

   class Container

     include Enumerable

     def each

       bi = BlockIterator.new

       @objects.each do |obj|
         bi.proxy = obj
         yield bi
       end

     end
   end

a module and dynamic object extension could also be used:

   module BlockIteratorProxyMethods
     ...
   end


   class Container
     def each
       @objects.each do |obj|
         obj.extend BlockIteratorProxyMethods
         yield obj
       end
     end
   end

you get the idea though...

another idea would be for the blocks to provide a LoopContext object - sort of
the state bit torn out from an iterator...

cheers.

-a
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