Whilst looking for some implementation of algorithms I found Rosetta Code, which is trying to show general algorithms in various languages. The 6502 section is severely lacking so could do with some expanding.

I've started by adding some code to do rot13 (which could be improved - it's currently at &37 bytes with no lookup tables, but a lot of cmps).

They also got no ARM snippets at all, which I may remediate if I have the time to remind myself how ARM code works...