How to building a parser using flex and bison

There is a simple demo about the program

This will be in C#.

Enter your code in the console below to check the syntax. Type 'exit' to quit! a-1; b -2; print a +b ; "a-1; b2; print a +b;" is a valid sentence >x=-42; y = a+1 ; print z; "X=-4^2; y = a+1 ; print z;" is a valid sentence "X!=4;" contains invalid lexemes, thus is not a valid sentence "X=-4;" is not a valid sentence. "x" is not a valid sentence. exit Exit! [02/10/191 seed@VM:-/.../assignmentls