The YACC Parser Generator/Example: Calculator with Variables

This example implements a simple calculator. The calculator has an unspecified number of integer variables and the common binary integer operators (namely, addition, subtraction, multiplication, division, and modulus), and unary integer operators (+ and -).

The Lexical Analyzer (Flex) Specification

The lexical analyzer is very simple and limited to recognizing variable names, integers numbers, and the operators themselves. <text> </text>