C++实现词法分析器

 /*************Written By Zzg************/      /*******Date : 11,25,2017********/ #include <iostream>#include <stdlib.h>#include <stdio.h> using namespace std;string KEYWORD[15]={"if","else","void","return","while","then","for","do",   //关键字          "int","char","double","float","case","cin","cout"};char SEPARATER[8]={';',',','{','}','[',']','(',')'};  //分隔符char OPERATOR[8]={'+','-','*','/','>','<','=','!'};   //运算符char FILTER[4]={' ','/t','/r','/n'};          //过滤符const int IDENTIFIER=100;     //标识符值const int CONSTANT=101;      //常数值const int FILTER_VALUE=102;    //过滤字符值  /**判断是否为关键字**/bool IsKeyword(string word){  for(int i=0;i<15;i++){    if(KEYWORD[i]==word){      return true;    }  }  return false;}/**判断是否为分隔符**/bool IsSeparater(char ch){  for(int i=0;i<8;i++){    if(SEPARATER[i]==ch){      return true;    }  }  return false;} /**判断是否为运算符**/bool IsOperator(char ch){  for(int i=0;i<8;i++){    if(OPERATOR[i]==ch){      return true;    }  }  return false;}/**判断是否为过滤符**/bool IsFilter(char ch){  for(int i=0;i<4;i++){    if(FILTER[i]==ch){      return true;    }  }  return false;}/**判断是否为大写字母**/bool IsUpLetter(char ch){  if(ch>='A' && ch<='Z') return true;  return false;}/**判断是否为小写字母**/bool IsLowLetter(char ch){  if(ch>='a' && ch<='z') return true;  return false;}/**判断是否为数字**/bool IsDigit(char ch){  if(ch>='0' && ch<='9') return true;  return false;}/**返回每个字的值**/template <class T>int value(T *a,int n,T str){ for(int i=0;i<n;i++){ if(a[i]==str) return i+1; } return -1;}/**词法分析**/void analyse(FILE * fpin){  char ch=' ';  string arr="";  while((ch=fgetc(fpin))!=EOF){    arr="";    if(IsFilter(ch)){}       //判断是否为过滤符    else if(IsLowLetter(ch)){    //判断是否为关键字      while(IsLowLetter(ch)){  arr += ch;  ch=fgetc(fpin);      }  //fseek(fpin,-1L,SEEK_CUR);  if(IsKeyword(arr)){        printf("%3d  ",value(KEYWORD,15,arr));  cout<<arr<<" 关键字"<<endl;  }  else      {        printf("%3d  ",IDENTIFIER);        cout<<arr<<" 标识符"<<endl;      }    }    else if(IsDigit(ch)){      //判断是否为数字      while(IsDigit(ch)||(ch=='.'&&IsDigit(fgetc(fpin)))){        arr += ch;        ch=fgetc(fpin);      }      fseek(fpin,-1L,SEEK_CUR);      printf("%3d  ",CONSTANT);      cout<<arr<<" 整形数"<<endl;    }    else if(IsUpLetter(ch)||IsLowLetter(ch)||ch=='_'){      while(IsUpLetter(ch)||IsLowLetter(ch)||ch=='_'||IsDigit(ch)){        arr += ch;        ch=fgetc(fpin);      }      fseek(fpin,-1L,SEEK_CUR);      printf("%3d  ",CONSTANT);      cout<<arr<<" 标识符"<<endl;    }    else switch(ch){    case '+':    case '-':    case '*':    case '/':    case '>':    case '<':    case '=':    case '!':      {        arr += ch;        printf("%3d  ",value(OPERATOR,8,*arr.data()));        cout<<arr<<" 运算符"<<endl;        break;      }    case ';':    case ',':    case '(':    case ')':    case '[':    case ']':    case '{':    case '}':      {       arr += ch;       printf("%3d  ",value(SEPARATER,8,*arr.data()));       cout<<arr<<" 分隔符"<<endl;       break;      }    default :cout<<"/""<<ch<<"/":无法识别的字符！"<<endl;    }  } }int main(){  char inFile[40];  FILE *fpin;  cout<<"请输入源文件名（包括路径和后缀）:";  while(true){    cin>>inFile;    if((fpin=fopen(inFile,"r"))!=NULL)      break;    else{      cout<<"文件名错误！"<<endl;      cout<<"请输入源文件名（包括路径和后缀）:";    }   }  cout<<"------词法分析如下------"<<endl;  analyse(fpin);  return 0;}