# File lib/core-uncommon/facets/module/let.rb, line 13
  def let(var,&block)
    name = "@#{var}"
    self.class_eval do
      define_method(var) do
        if instance_variable_defined?(name)
          instance_variable_get(name)
        else
          val = self.instance_eval(&block)
          instance_variable_set(name,val)
        end
      end
    end
  end