memoizer.rb

class Memoizer
  def initialize(tgt)
    @target = tgt
    @cache = {}
  end

  def cache(*method_names)
    method_names.each {|name| cache[name] = {} }
  end

  def method_missing(m, *a, &b)
    if @cache[m]
      @cache[m][a] ||= @target.send(m, *a, &b)
    else
      @target.send(m, *a, &b)
    end
  end
end