Attached is the software for which you paid several hundred pounds. It should work. Maybe on larger inputs it will fail. Sometimes several small parts of it will work, but when you put them together it will fail.
You see, there’s a maximum input data size for which it works. I don’t know exactly what that is, and it may vary according to your platform, configuration, or the day of the week.
On some platforms it might fail cleanly, on some it might segfault. We’re not sure.
(Our codebase is entirely tail-recursive, but people I’ve mentioned this to in passing seem to consider this an extreme position, citing loss of speed. Really?)