reference blog
https://dev.to/jrop/pratt-parsing
https://journal.stuffwithstuff.com/2011/03/19/pratt-parsers-expression-parsing-made-easy/
https://matklad.github.io/2020/04/13/simple-but-powerful-pratt-parsing.html
https://chidiwilliams.com/post/on-recursive-descent-and-pratt-parsing/