lex-wxw.cpp

词法分析程序 词法分析程序

#include<iostream>
#include<map>
#include<vector>
#include<fstream>
#include<string>
#include<utility>
#include<queue>
#include<conio.h>
using namespace std;
#define  MAX 20   //分析表的最大容量
#define  MAXBUF 255
char  ch =' ';   // 存放读入当前的输入字符
int lineno;    //行号 

struct reserve   //关键字
{
 char lexptr[MAXBUF];
 int token;
};

struct reserve symtable[MAX];
char * str[]={"include","main","using","namespace","endl","cout","cin","char","int","float",
              "double","while","for","if","then","else","do","return" };


void init()     //对符号表进行初始化
{
 for( int j=0; j<18; j++)
 { 
  strcpy(symtable[j].lexptr,str[j]);
  symtable[j].token=j+3;
 }
}
 

bool search(char *temp)
{
  string a=temp;
  string b="";
  for(int i=0; i<18;i++)
  {
      b=str[i];
      if(a==b) return true;
  }
  return false;
}     

 


void analyse(FILE *fpin,FILE *fpout)    //分析程序
{
     char arr[MAXBUF];
     int i=0;
     int j=0;
 
     while((ch=fgetc(fpin))!=EOF)    //读入字符判断，空格、字母、数字、界符
     {
           if(ch==' '||ch=='\t')
           {
   
           }
           else if(ch=='\n')    //如果是换行符，则行号加1
           {  
                lineno++;
           }
           else if(isdigit(ch))   //如果是数字
           { 
                while(isdigit(ch))   //判断和读取数字
                { 
                      arr[j]=ch;
                      j++;
                      ch=fgetc(fpin);
                } 
                arr[j]='\0';
                j=0;
                fseek(fpin,-1L,SEEK_CUR); //? 
                fprintf(fpout,"%s\t,常量\n",arr) ;
           }
           else if (isalpha(ch))  //如果是字母
           {
                while(isalpha(ch)||isdigit(ch))
                {
                    arr[j]=ch;
                    j++;
                    ch=fgetc(fpin);
                }
                fseek(fpin,-1L,SEEK_CUR);
                arr[j]='\0';
                j=0;
                if (search(arr)) //如果是关键字
                {
                    fprintf(fpout,"%s\t关键字\n",arr,search(arr));
                }
                else  
                    fprintf(fpout,"%s\t文字串\n",arr,1); //文字串 
           }
           else if(ch=='=')  
           {
                ch=fgetc(fpin);
                if(ch=='=') 
                {
                    fprintf(fpout,"%s\t赋值符\n","=");    //如果是 =
                }
                else
                {
                    fprintf(fpout,"%s\t普通符号\n",":");   //如果是 :
                    fseek(fpin,-1L,SEEK_CUR);
                }
           }
           else if (ch=='>')
           {
                ch=fgetc(fpin);
                if(ch=='=')    //如果是 >=
                {
                    fprintf(fpout,"%s\t普通符号\n",">=");
                }
                else
                {
                    fprintf(fpout,"%s\t普通符号\n",">");  //如果是 >
                    fseek(fpin,-1L,SEEK_CUR);
                }
           }
           else if(ch=='<')
           { 
                ch=fgetc(fpin);
                if(ch=='=')
                {
                     fprintf(fpout,"%s\t小于等于号\n","<=");   //如果是 <=
                }
                else 
                {
                     fprintf(fpout,"%s\t小于号号\n","<");   //如果是 <
                     fseek(fpin,-1L,SEEK_CUR);
                }
           }
           else if(ch=='/')
           { 
                ch=fgetc(fpin);
                if(ch=='*')
                {
                   ch=fgetc(fpin);
                   s:
                     while(ch!='*')
                     {
                           ch=fgetc(fpin);
                     }
                     while(ch=='*')
                     {
                           ch=fgetc(fpin);
                           while(ch!='/')
                           {
                           goto s;   //如果是注释 /*  */， 忽略，直到代码段 
                     }
                 }
           }
           else if(ch=='/')
           {
                   ch=fgetc(fpin);
                   while(ch!='\n')
                   {
                   ch=fgetc(fpin);   //如果是注释 //
                   }
           }
           else 
           {  
                   fprintf(fpout,"%s\t除法运算符\n","/");
                   fseek(fpin,-1L,SEEK_CUR);
           }
   }
  else if(ch=='+')
  {
           fprintf(fpout,"%s\t加法运算符\n","+");
  }
  else if(ch=='-')
  {
           fprintf(fpout,"%s\t减法运算符\n","-",22);
  }
  else if(ch=='*')
  {
   fprintf(fpout,"%s\t乘法运算符\n","*");
  }
  else if(ch=='(')
  {
   fprintf(fpout,"%s\t左括号\n","(");
  }
  else if(ch==')')
  {
   fprintf(fpout,"%s\t右括号\n",")");
  }
  else if(ch=='[')
  {
   fprintf(fpout,"%s\t左中括号\n","[");
  }
  else if(ch==']')
  {
   fprintf(fpout,"%s\t右中括号\n","]");
  }
  else if(ch=='{')
  {
   fprintf(fpout,"%s\t左花括号\n","(");
  }  
  else if(ch=='}')
  {
   fprintf(fpout,"%s\t右大括号\n","(");
  }
  else if(ch=='.')
  {
   fprintf(fpout,"%s\t成员引用符\n",".");
  }
  else if(ch==';')
  {
   fprintf(fpout,"%s\t标点符号\n",";");
  }
  else if(ch==',')
  {
   fprintf(fpout,"%s\t标点符号\n",",");
  }
  else if(ch=='#')
  {
   fprintf(fpout,"%s\t标识符\n","#");
  }
  else fprintf(fpout,"无法识别的字符 %c\n",ch)  ;
   }
} 


int main()
{
 cout<<"***************************词法分析器——>计科0502 王小伟 200542036*************************\n\n\n";
 //cout<<"直接输入源代码请按1，从文件中读入源代码请按2 \n" ;
 
 char filenamein[10];
 char filenameout[10];
   
 cout<<"请输入源文件名：\n";
 cin>>filenamein;
 cout<<"请输入保存词法分析结果的文件名：\n";
 cin>>filenameout;
 FILE* fpin=fopen(filenamein,"r");
 FILE* fpout=fopen(filenameout,"w");
 init();
 analyse(fpin,fpout);
 fclose(fpin);
 fclose(fpout);
 getch();
}