From: Intransition <transfire@...>
Date: 2010-04-08T06:49:15+09:00
Subject: Is it possible, a fully general Enumerable#recursive ?

For the last couple of days I've been trying to write an Enumerable
method called #recursive. Rather than create a bunch of methods like
#recursive_each, #recursive_map, #recursive_sort, etc. I figured that
it should be possible to create a single #recursive method that
returned an Enumerator, or barring that a Functor, that would handle
any enumerable method, e.g. recursive.each, recursive.map,
recursive.sort, and so on. But I have yet to figure out fully general
solution.

My nearest success thus far is:

  require 'facets/functor'

  module Enumerable

    def recursive
      Functor.new do |op,*a,&b|
        __send__(op) do |e|
          if self.class === e
            e.recursive.__send__(op,*a,&b)
          else
            b.call(e)
          end
        end
      end
    end

  end

This works for #each and #map but not #sort.

Can anyone think of a better solution?