编译原理算符优先文法自上而下的语法分析程序的算法-Principle of the priority operator compiler grammar parser top-down algorithm

用预测分析法实现自上而下的语法分析器（编译原理）-Using predictive analysis method to achieve a top-down parser (compiler principle)

该程序使用的自上而下的LL（1）分析法，，该文法不允许左递归，首先要消除左递归。(The program uses the top-down LL (1) analysis method, which does not allow left recursion, and the left recursion is first eliminated.)