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://github.com/arcosuc3m/clang-contracts/
https://llvm.org/devmtg/2019-04/slides/SRC-Lopez-Gomez-Adding_support_for_C++_contracts_to_clang.pdf
https://www.fi.muni.cz/~xtusil/cpp-contracts-1.html
https://www.modernescpp.com/index.php/c-core-guidelines-a-detour-to-contracts
https://habr.com/ru/post/443766/
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1290r1.pdf
https://cppeurope.com/wp-content/uploads/2018/03/contracts.pdf