C语言语法分析器

#include <stdio.h>
#include <string.h>
char prog[], token[];
char ch;
int syn,p,m,n,sum;
char * rwtab[]= {"begin","if","then","while","do","end"};

main()
{
      p=;
      printf("\n 请输入字符串: \n");
      do{
                 ch=getchar();
                 prog[p++]=ch;
      }while (ch!='#');
      p=;
      do{
          scaner();
          switch(syn)
                  {
                     case : printf("\n(%d,%d)",syn,sum); break;
                     case -: printf("\n(%s,出错!)",token);break;
                     default: printf("\n(%d,%s)",syn, token);
                  }
       }while (syn!=);
       printf("\n  分析成功 \n");
           p=;
    scaner();
     E();
     if (syn==)
              printf("\n 没有错误. \n");
     else     printf("\n  出现错误. \n");
}

scaner()
{
        for (n=;n<;n++) token[n]=NULL;
        m=;
        sum=;
        ch=prog[p++];
        while (ch==' ') {ch=prog[p++];}
        if (ch>='a'&& ch<='z')
           {while (ch>='a'&& ch<='z'||ch>='' && ch<='')
                  {
                   token[m++]=ch;
                   ch=prog[p++];
                  }

            syn=;p--;
            for (n=;n<;n++)
                if(strcmp(token,rwtab[n])==) {syn=n+;break;}
           }
 else
            if(ch>='' && ch<='')
            {while (ch>='' && ch<='') {sum=sum*+(ch-''); ch=prog[p++];}
             syn=;p--;
            }
          else
                switch(ch)
                {
                  case '<': token[m++]=ch;
                            ch=prog[p++];
                            if (ch=='>') {syn=;token[m++]=ch;}
                            else if (ch=='=') {syn=;token[m++]=ch;}
                                 else {syn=;p--;}
                            break;

                  case '>': m=; token[m++]=ch;
                            ch=prog[p++];
                            if (ch=='='){syn=;token[m++]=ch;}
                            else {syn=;p--;}
                            break;
                  case ':': m=; token[m++]=ch;
                            ch=prog[p++];
                            if (ch=='='){syn=;token[m++]=ch;}
                            else {syn=;p--;}
                            break;
                 case '+': syn=;token[]=ch;break;
                  case '-': syn=;token[]=ch;break;
                  case '*': syn=;token[]=ch;break;
                  case '/': syn=;token[]=ch;break;
                  case '=': syn=;token[]=ch;break;
                  case ';': syn=;token[]=ch;break;
                  case '(': syn=;token[]=ch;break;
                  case ')': syn=;token[]=ch;break;
                  case '#': syn=; token[]=ch;break;
                  default: syn=-;token[]=ch;
                }
}

E()
{printf("E ");
    T();
    E1();

}

E1()
{printf("E1 ");
    if (syn==) {
        scaner();
        T();
        E1();
    }
    else {
        if (syn!= && syn!=) error();
    }
} 

T()
{printf("T ");
    F();
    T1();
}

T1()
{printf("T1 ");
    if (syn==) {
        scaner();
        F();
        T1();
    }
    else {
        if (syn!= && syn!= && syn!=) error();
    }
}

F()
{printf("F ");
    if (syn==) {
        scaner();
        E();
        if(syn==) scaner();
        else error();
    }
    else if (syn== || syn==) scaner();

}
error()
{
    printf("\n (%d,%s)错误地方! \n",syn, token);
}

运行结果：