Flex Bison C++ Template is a code template that can be used to integrate a Flex scanner and Bison parser pair into a modern C++ program. These two universal tools are very difficult to incorporate into a good C++ design. The template utilizes both Flex and Bison in C++ mode and their output are encapsulated into classes. Thus the lexer and parser become fully reentrant, and multiple distinct lexer-parser pairs can easily be linked into one binary. The code implements a simple infix-notation calculator as an example, which can be used as a starting-point for you to insert your grammar.