- fprintf (stderr, "return_string");
- else if (is_function (op->operation))
- fprintf (stderr, "%s", operations[op->operation].prototype);
- else if (is_composite (op->operation))
- fprintf (stderr, "%s", operations[op->operation].name);
+ ds_put_cstr (&s, "return_string");
+ else if (is_function (op->operation))
+ ds_put_format (&s, "%s", operations[op->operation].prototype);
+ else if (is_composite (op->operation))
+ ds_put_format (&s, "%s", operations[op->operation].name);