class Module

def memoize_function(*function_ids)

function.
memoized result does ONLY depend on the arguments given to the
Automatically memoize calls of the functions +function_ids+. The 
def memoize_function(*function_ids)
  mc = @__memoize_cache__ ||= {}
  function_ids.each do |method_id|
    method_id = method_id.to_s.to_sym
    orig_method = instance_method(method_id)
    __send__(:define_method, method_id) do |*args|
      if mc.key?(method_id) and result = mc[method_id][args]
        result
      else
        (mc[method_id] ||= {})[args] = result = orig_method.bind(self).call(*args)
        $DEBUG and warn "#{self.class} cached function #{method_id}(#{args.inspect unless args.empty?}) = #{result.inspect}"
      end
      result
    end
  end
end