# File lib/mindi.rb, line 81
    def multiton(name, &impl) # :yields: arg
      impl_name = Container.impl_method_name(name)
      define_method(impl_name, &impl)
      
      ivname = Container.iv(name)
      define_method(name) do |key|
        map = instance_variable_get(ivname)
        map ||= instance_variable_set(ivname, {})
        map[key] ||= send(impl_name, key)
      end
    end