#include<stdio.h>
#include<string.h>
char character[80];//存放所有输入的字符
char token[8];//单词自身字符串
char ch;//单个字符
int sym;//sym:单词种别码
int p,m=0,i,row,sum=0;//sum:整型常数 row：记录新读入的字符行的行号
char*rwtab[6]={"begin","if","then","while","do","end"};
void scanner();
E();
E1();
T();
T1();
F();
error();


void main()
{
    p=0;
    row=1;
    printf("请输入一串字符串\n");
    do
    {
        ch=getchar();
        character[i++]=ch;
    }while(ch!=‘#‘);//输入以#号键结束
p=0;
do
{
  scanner();//识别单词
  switch(sym)
  {
    case 11:printf("(%d,%d)\n",sym,sum);break;
    case -1:printf("error in row %d!\n",row);break;
    case -2:row=row++;break;
    default:printf("(%d,%s)\n",sym,token);break;
  }
}while(sym!=0);
printf("\n  Token Over. \n");

    system("pause");
    p=0;
    scanner();
     E();
     if (sym==0)
              printf("\n Syntax success. \n");
     else     printf("\n  Syntax fail. \n");

}

//词法分析程序
void scanner()
{
    for(i=0;i<8;i++)
        token[i]=NULL;
       ch=character[p++];
    while(ch==‘ ‘)
    {
        ch=character[p];
        p++;
    }
    if((ch>=‘a‘&&ch<=‘z‘)||(ch>=‘A‘&&ch<=‘Z‘))//标识符或者变量名
    {
        m=0;
        while((ch>=‘0‘&&ch<=‘9‘)||(ch>=‘a‘&&ch<=‘z‘)||(ch>=‘A‘&&ch<=‘Z‘))
        {
            token[m++]=ch;
            ch=character[p++];
        }
            token[m++]=‘\0‘;
            p--;
            sym=10;
            for(i=0;i<6;i++)  //将识别出来的字符和已定义的标示符作比较，
            if(strcmp(token,rwtab[i])==0)
            {
                sym=i+1;
                break;
            }
    }
    else if((ch>=‘0‘&&ch<=‘9‘))//数字
    {
        sum=0;
        while((ch>=‘0‘&&ch<=‘9‘))
            {
                sum=sum*10+ch-‘0‘;
                ch=character[p++];

            }
            p--;
            sym=11;
            if(sum>32767)
                sym=-1;
    }
    else switch(ch)//其他字符
    {
    case‘<‘:m=0;token[m++]=ch;
        ch=character[p++];
        if(ch==‘=‘)
        {
            sym=21;
            token[m++]=ch;
        }
        else if(ch==‘>‘)
        {
            sym=22;
            token[m++]=ch;
        }
        else
        {
            sym=23;
            p--;
        }
        break;
    case‘>‘:m=0;token[m++]=ch;
       ch=character[p++];
       if(ch==‘=‘)
       {
           sym=24;
           token[m++]=ch;
       }
       else
       {
           sym=20;
           p--;
       }
       break;
    case‘:‘:m=0;token[m++]=ch;
       ch=character[p++];
       if(ch==‘=‘)
       {
           sym=18;
           token[m++]=ch;
       }
       else
       {
           sym=17;
           p--;
       }
       break;
        case‘+‘:sym=13;token[0]=ch;break;
        case‘-‘:sym=14;token[0]=ch;break;
        case‘*‘:sym=15;token[0]=ch;break;
        case‘/‘:sym=16;token[0]=ch;break;
        case‘=‘:sym=25;token[0]=ch;break;
        case‘;‘:sym=26;token[0]=ch;break;
        case‘(‘:sym=27;token[0]=ch;break;
        case‘)‘:sym=28;token[0]=ch;break;
        case‘#‘:sym=0;token[0]=ch;break;
        case‘\n‘:sym=-2;break;
        default:sym=-1;break;

    }
}
//E程序
E()
{
    printf("E ");
    T();
    E1();
}
E1()
{
       printf("E1 ");
    if(sym==13||sym==14 )
    {
    scanner();
    T();
    E1();
    }
    else {
        if (sym!=28 && sym!=0) error();
    }
}
T()
{
       printf("T ");
    F();
    T1();

}
T1()
{
       printf("T1 ");
    if(sym==15||sym==16)
    {
        scanner();
        F();
        T1();
    }
    else {
        if (sym!=28 && sym!=0 && sym!=13&& sym!=14) error();
    }
}
F()
{
       printf("F ");
    if(sym==27)
    {
        scanner();
        E();
        if(sym==28)
          scanner() ;
        else error();
    }
    else
    {
        if(sym==10||sym==11)
          scanner();
    }
}
error()
{
    printf("\n (%d,%s)Syntax Error! \n",sym, token);
}