I've written expression parsers many times in real life. I prefer recursive descent to shunting yard, though. But I think you mistake the purpose of the exercise. You do it in school because it will make you a better programmer. Programmers write
new things, and they link in or copy/paste things that have been done before. If you only want to learn stuff that is commonly done, then you want to be a copy/paster, not a programmer. —
Matt Timmermans 7 secs ago