working NudgeProgram#replace_point.rb

    def replace_point(which,new_junk)
      raise ArgumentError,"Cannot replace #{which}th program point" if which < 1
      raise ArgumentError,"Cannot replace #{which}th program point" if which > self.points
      raise ArgumentError,"Cannot insert #{new_junk.class}" unless new_junk.kind_of?(ProgramPoint)
      
      result = self.deep_copy
      
      if which == 1
        result.linked_code = new_junk
      else
        to_replace = result[which]
        parent = result.linked_code.detect do |wrapper|
          wrapper.contents.include?(to_replace) if wrapper.respond_to?(:contents)
        end
        parent_index = parent.contents.find_index(to_replace)
        parent.contents[parent_index] = new_junk
      end
      
      return result
    end