rb_define_method (c, "append_element", c_append_element, 1);
rb_define_method (c, "prepend_element", c_prepend_element, 1);
rb_define_method (c, "remove_element", c_remove_element, 1);
rb_define_method (c, "append_element", c_append_element, 1);
rb_define_method (c, "prepend_element", c_prepend_element, 1);
rb_define_method (c, "remove_element", c_remove_element, 1);