From: Intransition <transfire@...>
Date: 2010-10-08T00:02:47+09:00
Subject: Re: "map" a deeply nested structure: Object#deep_map

Perhaps what is being sought here is a form of search and replace.

  class Array
    def deep_replace(replacement, &match)
      map do |e|
        if e.respond_to?(:deep_replace)
          e.deep_replace(replacement, &match)
        else
          match[e] ? replacement : e
        end
    end
  end

  require 'facets/hash/mash'   #[1]

  class Hash
    def deep_replace(replacement, &match)
      mash do |k,v|
        nk = if k.respond_to?(:deep_replace)
          k.deep_replace(replacement, &match)
        else
          match[k] ? replacement : k
        end
        nv = if v.respond_to?(:deep_replace)
          v.deep_replace(replacement, &match)
        else
          match[v] ? replacement : v
        end
        [nk, nv]
    end
  end

Not tested but you get the idea.

I'm not 100% sure about handling the key for Hash either, but perhaps
an option could toggle that usage on or off.

[1]http://blog.thepete.net/2010/02/ruby-facets-mash-method.html