实验四 递归下降语法分析程序设计

#include<stdio.h>
char curr;
char LL1[1000];
int N=0;

void scaner();

int digital(){         //panduanshifouweishuzi

     if(curr >= '0' && curr <= '9')
     {
     return 1;
     }
     else {
     return 0;
     }

}

int english(){                   
   if(curr >= 'a' && curr<='z' || curr >= 'A' && curr <= 'Z')
   {
    return 1;
   }
  else 
      return 0;

}
int yuansuanf(){
  if(curr=='+'||curr=='-'||curr=='*'||curr=='/')
  {
  return 1;
  }
 
  else{
      return 0;
  }

}
int  end(){
    if(curr!='#'){
    return 1;    
    }
  else 
      return 0;
}


int check(){
      
     if(digital()==1){
          scaner();
          if(end()==1){
              if(yuansuanf()==1){
                  
                       return 1;
              }
              else if(yuansuanf()==0){
                        return 0;
              
              }
          }
          else if(end()==0){
          return 1;
          }
     
     }

       
         return 0;
    


}
 
void checking(){
   int number;
 qq:   scaner();
    if(digital()==1){
    while(curr!='#'){
      number=check();
      if(number==1){
         goto qq;
      }
      else if(number==0){
      
       break;     
      }
    }
    }


if(number==1){

printf("无错误");
}
else 
printf("%c错误",curr);


}



void main()
{    char ch;
    int i=0;
    printf("请输入需要分析的语法：(#结束)
");

    do{
        scanf("%c",&ch);
        LL1[i] = ch;
        i++;
    }while(ch != '#');
    scaner();
    checking();
    

}

void scaner(){   //用于读取源函数的下一个字符

    N++;
    if(LL1[N] == ' '){
        N++;
    }else
    {
        curr = LL1[N];
    }
}