- double new_value = can->func (input, can->n++, can->aux);
- case_nullify (output);
- case_move (output, input);
- case_resize (output, can->value_ofs + 1);
- case_data_rw_idx (output, can->value_ofs)->f = new_value;
+ double new_value = can->func (c, can->n++, can->aux);
+ c = case_unshare_and_resize (c, can->value_ofs + 1);
+ case_data_rw_idx (c, can->value_ofs)->f = new_value;
+ return c;