词法分析器
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作者：朱鑫
邮箱：zhuxin@nwsuaf.edu.cn
/*C语言词法分析器，从三个方面处理:关键字，运算符，界符。并且将输出，符号，常数输出到文件,可以忽略同一行的注释//-1 error,代表错误//保留字1auto 2break 3case 4char 5const 6continue 7default 8do9double 10else 11enum 12extern 13float 14for 15goto 16if17int 18long 19register 20return 21short 22signed 23static 24sizeof25struct 26switch 27typedef 28union 29unsigned 30void 31volatile 32while//运算符33= 34==35+ 36++ 37+=38- 39-- 40-= 41->42* 43*=44/ 45/=46% 47%=48(49)50[51]52,53> 54>> 55>>= 56>=57< 58<< 59<<= 60<=61! 62!=63^ 64^=65& 66&& 67&=68| 69|| 70|=71~72? :73.//界符74{75}76；77\//注释78 ////79标示符//80常数*/#include<iostream>#include<fstream>#include<cstdlib>using namespace std;string Keyword[]={"","auto","break","case","char","const","continue","default","do", "double","else","enum","extern","float","for","goto","if", "int","long","register","return","short","signed","static","sizeof", "struct","switch","typedef","union","unsigned","void","volatile","while" };string ID[1000]; //符号表int indexOfID=0;string Const[1000]; //常数表int indexOfConst=0;bool IsLetter(char ch); //判断是不是字母或下划线bool IsDigit(char ch); //判断是不是数字int Reserve(string strToken); //查询是否是关键字，不是的话返回0，是的话返回ID(二分查找)void insertID(string strToken); //插入符号表void insertConst(string strToken); //插入常数表int main(void){ int code=0,lineAt=0; //ID号及行号 string line; //一行 int i; int length=0; string strToken=""; char ch; ifstream in; //从文件中读取 ofstream out; //输出到文件 ofstream IDOut; //符号表 ofstream ConstOut; //常数表 in.open("in.txt",ios::in); if(!in) { cerr<<"File open or create error!"<<endl; exit(1); } out.open("out.txt",ios::out); IDOut.open("IDOut.txt",ios::out); ConstOut.open("ConstOut.txt",ios::out); while(getline(in,line)) { lineAt++; if((length=line.length())==0) { continue; } i=0; while(i<=length) { while(line[i]==' '||line[i]=='\t'||line[i]=='\n') { i++; } ch=line[i]; if(ch=='\0') { break; } strToken+=ch; //字母 if(IsLetter(ch)) { while( IsLetter(line[++i]) || IsDigit(line[i]) ) { strToken+=line[i]; } i--; code=Reserve(strToken); if(code==0) { code=79; insertID(strToken); } } //数字 else if(IsDigit(ch)) { while(IsDigit(line[++i])) { strToken+=line[i]; } i--; code=80; insertConst(strToken); } //等号 else if(ch=='=') { if(line[++i]=='=') { code=34; strToken+='='; } else { i--; code=33; } } //加号 else if(ch=='+') { if(line[++i]=='+') { code=36; strToken+='+'; } else if(line[i]=='=') { code=37; strToken+='='; } else { i--; code=35; } } //减号 else if(ch=='-') { if(line[++i]=='-') { code=39; strToken+='-'; } else if(line[i]=='=') { code=40; strToken+='='; } else if(line[i]=='>') { code=41; strToken+='>'; } else { i--; code=38; } } //乘号 else if(ch=='*') { if(line[++i]=='=') { code=43; strToken+='='; } else { i--; code=42; } } //除号 else if(ch=='/') { if(line[++i]=='=') { code=45; strToken+='='; } else if(line[i]=='/') { code=78; strToken+='/'; cout<<"( "<<lineAt<<","<<"\""<<code<<"\""<<","<<"\""<<strToken<<"\""<<" )"<<endl; out<<"( "<<lineAt<<","<<"\""<<code<<"\""<<","<<"\""<<strToken<<"\""<<" )"<<endl; strToken=""; break; } else { i--; code=44; } } // else if(ch=='%') { if(line[++i]=='=') { code=47; strToken+='='; } else { i--; code=46; } } //括号 else if(ch=='(') { code=48; } else if(ch==')') { code=49; } else if(ch=='[') { code=50; } else if(ch==']') { code=51; } else if(ch==',') { code=52; } //大于号 else if(ch=='>') { if(line[++i]=='>') { strToken+='>'; if(line[++i]=='=') { code=55; strToken+='='; i++; } else { i--; code=54; } } else if(line[i]=='=') { code=56; strToken+='='; i++; } else { i--; code=53; } } //小于号 else if(ch=='<') { if(line[++i]=='<') { strToken+='<'; if(line[++i]=='=') { code=59; strToken+='='; } else { i--; code=58; } } else if(line[i]=='=') { code=60; strToken+='='; } else { i--; code=57; } } //非号 else if(ch=='!') { if(line[++i]=='=') { code=62; strToken+='='; } else { i--; code=61; } } // else if(ch=='^') { if(line[++i]=='=') { code=64; strToken+='='; } else { i--; code=63; } } // else if(ch=='&') { if(line[++i]=='&') { code=66; strToken+='&'; } else if(line[i]=='=') { code=67; strToken+='='; } else { i--; code=65; } } // else if(ch=='|') { if(line[++i]=='|') { code=69; strToken+='|'; } else if(line[i]=='=') { code=70; strToken+='='; } else { i--; code=68; } } // else if(ch=='~') { code=71; } else if(ch=='?') { code=72; } else if(ch=='.') { code=73; } else if(ch=='{') { code=74; } else if(ch=='}') { code=75; } else if(ch==';') { code=76; } else if(ch=='\\') { code=77; } else { code=-1; } i++; if(strToken.length()>1) { cout<<"( "<<lineAt<<","<<"\""<<code<<"\""<<","<<"\""<<strToken<<"\""<<" )"<<endl; out<<"( "<<lineAt<<","<<"\""<<code<<"\""<<","<<"\""<<strToken<<"\""<<" )"<<endl; } else { cout<<"( "<<lineAt<<","<<"\""<<code<<"\""<<","<<"\""<<ch<<"\""<<" )"<<endl; out<<"( "<<lineAt<<","<<"\""<<code<<"\""<<","<<"\""<<ch<<"\""<<" )"<<endl; } strToken=""; } } for(int i=0;i<indexOfID;i++) { IDOut<<i<<"\t"<<ID[i]<<endl; } for(int i=0;i<indexOfConst;i++) { ConstOut<<i<<"\t"<<Const[i]<<endl; } in.close(); out.close(); IDOut.close(); ConstOut.close(); return 0;}bool IsLetter(char ch){ if( (ch>='a'&&ch<='z') || (ch>='A'&&ch<='Z') || ch=='_') { return true; } return false;}bool IsDigit(char ch){ if(ch>='0'&&ch<='9') { return true; } return false;}int Reserve(string strToken){ int left=1; int right=32; int middle; while(left<=right) { middle=(left+right)/2; if(Keyword[middle]==strToken) { return middle; } else if(Keyword[middle]>strToken) { right=middle-1; } else { left=middle+1; } } return 0;}void insertID(string strToken){ for(int i=0;i<indexOfID;i++) { if(strToken==ID[i]) { return ; } } ID[indexOfID++]=strToken;}void insertConst(string strToken){ for(int i=0;i<indexOfConst;i++) { if(strToken==Const[i]) { return ; } } Const[indexOfConst++]=strToken;}- 词法分析器
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