词法分析程序

#include <stdio.h>    
#include <string.h>       
char prog[80],token[8],ch;    
int syn,p,m,n,sum;    
char *rwtab[6]={"begin","if","then","while","do","end"};         
void scaner(void);        
main()    
{    
    p=0;    
    printf("\n please input a string(end with ‘#‘):\n");    
        
    do{    
            scanf("%c",&ch);    
            prog[p++]=ch;    
    }while(ch!=‘#‘);    
        
    p=0;    
    do{    
            scaner();    
            switch(syn)    
            {    
                case 11:    
                    printf("( %-10d%5d )\n",sum,syn);    
                break;    
                    
                case -1:    
                    printf("you have input a wrong string\n");    
                    //getch();    
                    return 0;    
                break;    
                    
                default:     
                printf("( %-10s%5d )\n",token,syn);    
                break;    
            }    
        }while(syn!=0);    
    return 0;//getch();    
 }    
    
void scaner()    
{      
    sum=0;    
    for(m=0;m<8;m++)    
        token[m]=0;    
        ch=prog[p++];    
        m=0;              
    while((ch==‘ ‘)||(ch==‘\n‘))    
        ch=prog[p++];      
    if(((ch<=‘z‘)&&(ch>=‘a‘))||((ch<=‘Z‘)&&(ch>=‘A‘)))//可能是标示符或者变量名    
     {     
        while(((ch<=‘z‘)&&(ch>=‘a‘))||((ch<=‘Z‘)&&(ch>=‘A‘))||((ch>=‘0‘)&&(ch<=‘9‘))) //找到一个变量名或者关键字，直到遇到空格为止   
        {    
            token[m++]=ch;    
            ch=prog[p++];    
        }                
        p--;    
        syn=10;    
        for(n=0;n<6;n++)    //将识别出来的字符和已定义的标示符作比较
        if(strcmp(token,rwtab[n])==0)    
        {     
            syn=n+1;    
            break;    
        }    
     }    
     else if((ch>=‘0‘)&&(ch<=‘9‘)) //数字    
     {     
        while((ch>=‘0‘)&&(ch<=‘9‘))    
        {    
            sum=sum*10+ch-‘0‘; //将字符串转换成数字   
            ch=prog[p++];    
        }    
        p--;    
        syn=11;    
    }    
    else     
    {    
        switch(ch)    //其它字符
        {    
        case ‘<‘:    
            token[m++]=ch;    
            ch=prog[p++];    
            if(ch==‘=‘)    
            {     
                syn=22;    
                token[m++]=ch;    
            }    
            else    
            {      
                syn=20;    
                p--;    
            }    
        break;    
    
        case ‘>‘:    
            token[m++]=ch;    
            ch=prog[p++];    
            if(ch==‘=‘)    
            {    
                syn=24;    
                token[m++]=ch;    
            }    
            else    
            {     
                syn=23;    
                p--;    
            }    
        break;    
    
        case ‘+‘:    
            token[m++]=ch;    
            ch=prog[p++];    
            if(ch==‘+‘)    
            {    
                syn=17;    
                token[m++]=ch;    
            }    
            else    
            {    
                syn=13;    
                p--;    
            }    
        break;    
    
        case ‘-‘:    
            token[m++]=ch;    
            ch=prog[p++];    
            if(ch==‘-‘)    
            {    
                syn=29;    
                token[m++]=ch;    
            }    
            else    
            {     
                syn=14;    
                p--;    
            }    
        break;    
    
        case ‘!‘:    
            ch=prog[p++];    
            if(ch==‘=‘)    
            {     
                syn=21;    
                token[m++]=ch;    
            }    
            else    
            {     
                syn=31;    
                p--;    
            }    
        break;    
    
        case ‘=‘:    
            token[m++]=ch;    
            ch=prog[p++];    
            if(ch==‘=‘)    
            {    
                syn=25;    
                token[m++]=ch;    
            }    
            else    
            {    
                syn=18;    
                p--;    
            }    
        break;    
    
        case ‘*‘:    
            syn=15;    
            token[m++]=ch;    
        break;    
    
        case ‘/‘:    
            syn=16;    
            token[m++]=ch;    
        break;    
    
        case ‘(‘:     
            syn=27;    
            token[m++]=ch;    
        break;    
    
        case ‘)‘:    
            syn=28;    
            token[m++]=ch;    
        break;    
    
        case ‘{‘:     
            syn=5;    
            token[m++]=ch;    
        break;    
    
        case ‘}‘:     
            syn=6;    
            token[m++]=ch;    
        break;    
    
        case ‘;‘:    
            syn=26;    
            token[m++]=ch;    
        break;    
    
        case ‘\"‘:    
            syn=30;    
            token[m++]=ch;    
        break;    
    
        case ‘#‘:     
            syn=0;    
            token[m++]=ch;    
        break;    
    
        case ‘:‘:    
            syn=17;    
            token[m++]=ch;    
        break;    
    
        default:    
            syn=-1;    
        break;    
        }    
    }    
        token[m++]=‘\0‘;    
}