https://www.coldfix.eu/2015/05/16/bison-c++11/
https://www.geeksforgeeks.org/flex-fast-lexical-analyzer-generator/
http://anoopsarkar.github.io/compilers-class/yacc-practice.html
vid calculator written with flex/bison
https://nullprogram.com/blog/2019/01/25/
books
courses
https://research-information.bristol.ac.uk/files/142141947/%7C
Un-preprocessing: Extended CPP that works with your tools∗