Multiple prefix ops allowed

[jozsef-ostor]

I think the parser should refuse
--1
++1

[cosinekitty]

Those are odd inputs, and they would be rejected by a C/C++ compiler because -- and ++ are operator tokens. However, my goal for this Medium article was to present something simple so people could understand recursive descent parsers. So I chose a math display formatter, not a programming language. Although --1 looks strange, it is really the same thing as -(-1), which is valid.

However, it would be a good exercise if you want, to fork this project and see if you can update the parser to reject such input strings.