学习简单的Yacc说明的原理，掌握Yacc源文件的写法以及语法分析器生成工具BISON的使用方法和Yacc源文件的运行方法和基本步骤。 -Yacc study shows a simple principle, Yacc master source file written syntax analyzer and generate UML tools and the use of the source language Yacc pieces of the operation and bas