I mean, how can you not love: expr: [term ["+" | "-"] expr | term] term: [factor ["*" | "/"] term | factor] factor: [primary "**" factor | primary

I mean, how can you not love: expr: [term ["+" | "-"] expr | term] term: [factor ["*" | "/"] term | factor] factor: [primary "**" factor | primary] primary: [some digit | "(" expr ")"] digit: charset "0123456789"