编译原理--语法分析 实验 （C++版）

// BianYiYuanLi2.cpp: 定义控制台应用程序的入口点。 // #include "stdafx.h" #include <string> #include <iostream> void E(int& TZ, std::string& ST); void ADVANCE(std::string& ST) { ST.erase(0, 1); } char SYM(std::string& ST) { std::string::iterator it = ST.begin(); return *it; } void F(int& TZ, std::string& ST) {//(SYM >= 'a'&&SYM <= 'z') || if ((SYM(ST) >= 'A'&&SYM(ST) <= 'Z')) { ADVANCE(ST); return; } else { if (SYM(ST) != '(') { //std::cout << "ERROR" << std::endl; TZ = 1; return; } else { ADVANCE(ST); E(TZ, ST); if (SYM(ST) != ')') { std::cout << "ERROR" << std::endl; TZ = 1; return; } else { ADVANCE(ST); return; } } } } void T(int& TZ, std::string& ST) { F(TZ, ST); while (SYM(ST) == '*' || SYM(ST) == '/') { ADVANCE(ST); F(TZ, ST); } } void E(int& TZ, std::string& ST) { do { T(TZ, ST); if (SYM(ST) == '+' || SYM(ST) == '-') { ADVANCE(ST); } else { return; } } while (true); } int main() { while (true) { std::cout << "Input Expression" << std::endl; //接受输入的表达式 std::string ST; std::cin >> ST; int TZ = 0; E(TZ, ST); if (SYM(ST) != '#' || TZ == 1) { std::cout << "ERROR AGAIN!"; TZ = 0; } else { std::cout << "RIGHT AGAIN!"; } system("pause"); } return 0; }