rb_define_method (c, "keys", c_keys, 0);
rb_define_method (c, "values", c_values, 0);
rb_define_method (c, "merge!", c_merge, 1);
rb_define_method (c, "keys", c_keys, 0);
rb_define_method (c, "values", c_values, 0);
rb_define_method (c, "merge!", c_merge, 1);