PASCAL语法分析

Pascal语言的语法分析器基于文档最下面词法分析器写的#include<iostream>#include<cstring>#include<fstream>#include<sstream>#include<string>using namespace std;fstream f;char ch,ch1[100];intcla,no,num;stringstr;//program 1 1//var 1 2//begin 1 3//end 1 4//integer 1 5//real 1 6//while 1 7//if 1 8//then 1 9//else 1 10//do 1 11//";" 5,0//"." 6,0//":" 7,0//"," 8,0//":=" 9,0//"+" 10,0;//"-" 11,0//"*" 12,0//"/" 13,0//"<" 14,0//"<=" 15,0//"=" 16,0;//">" 17,0//">=" 18,0//"<>" 19,0//"||" 20,0//"&" 21,0//"!" 22,0//"(" 23,0//")" 24,0 void scan(){f.getline(ch1,100);stringstreamss(ch1);ss>>ch>>cla>>ch>> no >>ch>>str;}boolisprogram();bool variable();bool constant();bool factor();bool term();bool arithmetic();bool assignment();bool relation();bool condition();bool repeat();bool complex();bool statement();boolstatementlist();bool block();bool judge();int main(){f.open("out.txt",ios::in);bool flag = false;num = 0;if(judge()){flag = true;}if(flag){//判断是不是程序cout<< "It is a program!" <<endl;}else{cout<< "It is not a program!" <<endl;}system("pause");return 0;}boolisprogram(){//判断程序scan();//判断progreamif(cla != 1 && no != 1) return false;scan();//判断程序名if(cla != 3 && no != 1) return false;num++;scan();//判断分号if(cla != 5 && no != 0) return false;scan();//判断varif(cla != 1 && no != 2) return false;while(true){//if(cla == 1 && no == 3) break;//如果遇到begin 跳出//if(cla != 3) return false;//既不是begin也不是变量while(true){scan();if(cla == 1 && no == 3) return true;else if(cla == 3){num++;}else return false;scan();if(cla != 8){//不是，跳出break;}}if(cla != 7) return false;//不是：scan();if(cla != 1 && (no != 5 || no != 6)) return false;//不是intger realscan();if(cla != 5) return false;}return true;}bool variable(){//变量scan();if(cla == 3 ) return true;else{f.unget();return false;}}bool constant(){//常数scan();if(cla != 2 &&cla != 6){//2为整数6为.f.unget();return false;}if(cla == 2){//前面是整数，scan();if(cla != 6){//后面不是点，则返回，此数为整数f.unget();return true;}else{//后面是点scan();if(cla != 2){//点后面不是整数返回falsef.unget();return false;}return true;}}else if(cla == 6){//前面是.scan();if(cla != 2){//点后面不是整数返回falsef.unget();return false;}return true;}}bool factor(){//因式if(variable()) return true;//变量else if(constant()) return true;//常数scan();if(cla == 23){if(!arithmetic()) return false;//算术表达式scan();if(cla == 24) return true;f.unget();return false;}f.unget();return false;}bool term(){//项if(factor()){scan();if(cla != 12 &&cla != 13){f.unget();return true;}else{if(term()) return true;return false;}}return false;}bool arithmetic(){//判断算术表达式if(term()){scan();if(cla != 10 &&cla != 11){f.unget();return true;}if(arithmetic()) return true;return false;}}bool assignment(){//赋值scan();if(cla != 3){f.unget();return false;}//判断变量scan();if(cla != 9 || no != 0){f.unget();return false;}//判断:=if(!arithmetic()) return false;/*scan();if(cla != 5) return false;*/return true;}bool relation(){//关系表达式if(!arithmetic()) return false;scan();if(cla == 14 || cla == 15 || cla == 16 || cla == 17 || cla == 18 || cla == 19){//如果是关系运算符if(!arithmetic()){f.unget();return false;}return true;}f.unget();//如果不是关系运算符return false;}bool condition(){//条件scan();if(cla != 1 || no != 8){//iff.unget();return false;}int flag = 0;while(true){scan();if(cla != 23){f.unget();//判断是否有（有的话过滤掉break;}flag++;}int nr = 0;while(true){scan();if(cla != 20 &&cla != 21 &&cla != 22){if(cla == 24) {f.unget();break;}//遇到）跳出if(cla == 1 && no == 9){//遇到then返回f.unget();break;}f.unget();}intfl = 0;while(true){scan();if(cla != 23){f.unget();//判断是否有（有的话过滤掉break;}fl++;}if(!relation()){//关系表达式return false;}nr++;if(nr == 1){while(true){scan();if(cla == 24) flag--;if(fl == 0){//关系表达式的右括号等于左括号跳出break;}}}if(nr != 1){while(true){scan();if(cla == 24) fl--;if(fl == 0){//关系表达式的右括号等于左括号跳出break;}}}}while(true){//判断（==）scan();if(cla != 24){f.unget();//判断是否有（有的话过滤掉break;}flag--;}if(flag != 0) return false;scan();if(cla != 1 || no != 9){//thenf.unget();return false;}if(!statement()) return false;//语句scan();if(cla != 1 || no != 10){//elsef.unget();return false;}if(!statement()) return false;//语句return true;}bool repeat(){//whilescan();if(cla != 1 || no != 7){f.unget();return false;}if(!relation()) return false;scan();if(cla != 1 || no != 11){f.unget();return false;}if(!statement()) return false;return true;}bool complex(){//复合f.getline(ch1,100);stringstreamss(ch1);ss>>ch>>cla>>ch>> no >>ch>>str;if(cla != 1 || no != 3){f.unget();return false;}if(!statementlist())return false;f.getline(ch1,100);ss<< ch1;ss>>ch>>cla>>ch>> no >>ch>>str;if(cla != 1 || no != 4){f.unget();return false;}return true;}bool statement(){//语句判断函数bool a = assignment();if(a) return true;//赋值bool b = condition();if(b) return true;//条件bool c = repeat();if(c) return true;//whilebool d = complex();if(d) return true;//复合//if(a || b || c || d) return true;return false;}boolstatementlist(){//语句表判断函数if(!statement()) return false;//不是语句返回false scan();if(cla != 5){//是语句后面不是分号if(cla == 1 && no == 4){return true;}f.unget();return false;}if(!statementlist()){//后面分号但后面不是语句表。