编译原理语法分析。自顶向下分析语法，首先要分析词法是否正确，若错误有错误提示，若没有进行语法分析自顶向下匹配字符串，显示匹配成功，或者失败结果。-Parsing compiler theory. Top-down analysis of grammar, lexical analysis is correct first, if an error has error, if there is no top-down parsing strings match, display matching success or failure results.