语法分析器：递归下降子程序的编写

通过本实验，了解递归下降预测分析的原理和过程以及可能存在的回溯问题，探讨解决方法，为预测分析表方法的学习奠定基础。分析递归下降子程序的优缺点。-Parser: recursive descent routines written by this study to understand the principle of recursive descent and the process of predictive analysis, and possible back problems, explore solutions, methods for the prediction of the table lay the foundation for learning. The advantages and disadvantages of recursive descent subprogram.