词法分析

#include<stdio.h>
#include<string.h>
char prog[80],token[8];
char ch;
int syn,p,m=0;
int n,row,sum=0;
char *rwtab[6]={"begin","if","then","while","do","end"};
void get1()
{
    /*分3块,标识符，数字，符号3块，分别对应if，else——if和else*/
    for(n=0;n<8;n++)
        token[n]=NULL;
    ch=prog[p++];
   while((ch==‘ ‘)||(ch==‘/n‘))
    {
        ch=prog[p];
        p++;
    }
    if((ch>=‘a‘&&ch<=‘z‘)||(ch>=‘A‘&&ch<=‘Z‘))//标识符或变量名
    {
        m=0;
        while((ch>=‘0‘&&ch<=‘9‘)||(ch>=‘a‘&&ch<=‘z‘)||(ch>=‘A‘&&ch<=‘Z‘))
        {
            token[m++]=ch;
            ch=prog[p++];
        }
        token[m++]=‘\0‘;
        p--;
        syn=10;
        for(n=0;n<6;n++)
        {
            if(strcmp(token,rwtab[n])==0)
        {
            syn=n+1;
            break;
        }
        }
    }
        else if(ch>=‘0‘&&ch<=‘9‘)//number
        {
           sum=0;
           while(ch>=‘0‘&&ch<=‘9‘)
           {
               sum=sum*10+ch-‘0‘;
               ch=prog[p++];
           }
           p--;
           syn=11;

        }
        else {
            switch(ch)//other string
            {
                case‘<‘:
                    m=0;
                    token[m++]=ch;
                    ch=prog[p++];
                    if(ch=‘>‘)
                    {
                        syn=22;
                    }
                    else if(ch==‘=‘)
                    {
                        syn=21;
                        token[m++]=ch;
                    }
                    else
                    {
                        syn=20;
                        p--;
                    }break;
                case‘>‘:
                    m=0;
                    token[m++]=ch;
                    ch=prog[p++];
                    if(ch==‘=‘)
                    {
                        syn=24;
                        token[m++]=ch;
                    }
                    else
                    {
                        syn=23;
                        p--;
                    }break;
                case‘:‘:
                    m=0;
                    token[m++]=ch;
                    ch=prog[p++];
                    if(ch==‘=‘)
                    {
                        syn=18;
                        token[m++]=ch;
                    }
                    else
                    {
                        syn=17;
                        p--;
                    }break;
                    case‘*‘:syn=11;token[0]=ch;break;
                    case‘/‘:syn=16;token[0]=ch;break;
                    case‘+‘:syn=13;token[0]=ch;break;
                    case‘-‘:syn=14;token[0]=ch;break;
                    case‘=‘:syn=25;token[0]=ch;break;
                    case‘;‘:syn=26;token[0]=ch;break;
                    case‘(‘:syn=27;token[0]=ch;break;
                    case‘)‘:syn=28;token[0]=ch;break;
                    case‘#‘:syn=0;token[0]=ch;break;
                    case‘\n‘:syn=-2;break;
                    default: syn=-1;break;

            }
        }

}
int main()
{
    p=0;
    row=1;
    printf("输入一串字符串(以#结束)：");
    do
    {
        scanf("%c",&ch);
        prog[p++]=ch;
    }while(ch!=‘#‘);

    p=0;
    do
    {
        get1();
        switch(syn)
        {
            case 11:
                printf("(%d,%d)",syn,sum);
                break;
            case -1:
               printf("错误（row）！");
               getch();
               break;
            case -2:
                row=row++;
                break;
            default:
                printf("(%d,%s)",syn,token);
                break;
        }
    }while(syn!=0);
    getch();

}