编译原理实验1

clude  
#include  
#include  
#define KEYWORDEND "waiting for your expanding"  
  
typedef struct  
{  
    int typenum;  
    char *word;  
} WORD;  
  
char input[255];  
char token[255]="";  
int pinput;  
int ptoken;  
char ch;  
char *rwtab[]= {"begin","if","then","while","do","end",KEYWORDEND};  
  
WORD *scaner();  
  
int main()  
{  
    int over=1;  
    WORD *oneword=new WORD;  
    printf ("enter your words(end with #):");  
    scanf("%[^#]s",input);  
    pinput=0;  
    printf ("your words:\n%s\n",input);  
    while(over<1000 && over!=-1)  
    {  
        oneword=scaner();  
        if (oneword->typenum<1000)  
            printf ("(%d,%s)",oneword->typenum,oneword->word);  
        over=oneword->typenum;  
    }  
    printf("\npress # to exit:");  
    scanf("%[^#]s",input);  
    return 0;  
}  
  
char mgetch()           //读取一个字符到ch  
{  
    ch=input[pinput];  
    pinput=pinput+1;  
    return(ch);  
}  
  
void getbc()            //去掉空白符号  
{  
    while(ch==' ' || ch==10)  
    {  
        ch=input[pinput];  
        pinput=pinput+1;  
    }  
}  
  
void concat()  
{  
    token[ptoken]=ch;  
    ptoken=ptoken+1;  
    token[ptoken]='\0';  
}  
  
int letter()  
{  
    if (ch>='a' && ch<='z'||ch>='A'&&ch<='z')return 1;  
    else  
        return 0;  
}  
  
int digit()  
{  
    if (ch>='0' && ch<='9') return 1;  
    else return 0;  
}  
  
int reserve()  
{  
    int i=0;  
    while(strcmp(rwtab[i],KEYWORDEND))  
    {  
        if(!strcmp(rwtab[i],token))  
        {  
            return i+1;  
        }  
        i=i+1;  
    }  
    return 10;  
}  
  
void retract()  
{  
    pinput=pinput-1;  
}  
  
char *dtb()  
{  
    return NULL;  
}  
  
WORD *scaner()  
{  
    WORD *myword=new WORD;  
    myword->typenum=10;  
    myword->word="";  
    ptoken=0;  
    mgetch();  
    getbc();  
    if (letter())  
    {  
        while(letter() || digit())  
        {  
            concat();  
            mgetch();  
        }  
        retract();  
        myword->typenum=reserve();  
        myword->word=token;  
        return(myword);  
    }  
    else if(digit())  
    {  
        while(digit())  
        {  
            concat();  
            mgetch();  
        }  
        retract();  
        myword->typenum=11;  
        myword->word=token;  
        return(myword);  
    }  
    else switch(ch)  
        {  
        case'=':  
            mgetch();  
            if (ch=='=')  
            {  
                myword->typenum=39;  
                myword->word="==";  
                return(myword);  
            }  
            retract();  
            myword->typenum=21;  
            myword->word="=";  
            return(myword);  
            break;  
        case'+':  
            myword->typenum=13;  
            myword->word="+";  
            return(myword);  
            break;  
        case'-':  
            myword->typenum=14;  
            myword->word="-";  
            return(myword);  
            break;  
        case'*':  
            myword->typenum=15;  
            myword->





word="*";  
            return(myword);  
            break;  
        case'/':  
            myword->typenum=16;  
            myword->word="/";  
            return(myword);  
            break;  
        case'(':  
            myword->typenum=27;  
            myword->word="(";  
            return(myword);  
            break;  
        case')':  
            myword->typenum=28;  
            myword->word=")";  
            return(myword);  
            break;  
        case'[':  
            myword->typenum=28;  
            myword->word="[";  
            return(myword);  
            break;  
        case']':  
            myword->typenum=29;  
            myword->word="]";  
            return(myword);  
            break;  
        case'{':  
            myword->typenum=30;  
            myword->word="{";  
            return(myword);  
            break;  
        case'}':  
            myword->typenum=31;  
            myword->word="}";  
            return(myword);  
            break;  
        case',':  
            myword->typenum=32;  
            myword->word=",";  
            return(myword);  
            break;  
        case':':  
            mgetch();  
            if (ch=='=')  
            {  
                myword->typenum=18;  
                myword->word=":=";  
                return(myword);  
            }  
            retract();  
            myword->typenum=17;  
            myword->word=":";  
            return(myword);  
            break;  
        case';':  
            myword->typenum=26;  
            myword->word=";";  
            return(myword);  
            break;  
        case'>':  
            mgetch();  
            if (ch=='=')  
            {  
                myword->typenum=37;  
                myword->word=">=";  
                return(myword);  
            }  
            retract();  
            myword->typenum=35;  
            myword->word=">";  
            return(myword);  
            break;  
        case'<':  
            mgetch();  
            if (ch=='=')  
            {  
                myword->typenum=38;  
                myword->word="<=";  
                return(myword);  
            }  
            if (ch=='>')  
            {  
                myword->typenum=21;  
                myword->word="<=";  
                return(myword);  
            }  
            retract();  
            myword->typenum=20;  
            myword->word="<";  
            return(myword);  
            break;  
        case'!':  
            mgetch();  
            if (ch=='=')  
            {  
                myword->typenum=40;  
                myword->word="!=";  
                return(myword);  
            }  
            retract();  
            myword->typenum=-1;  
            myword->word="ERROR";  
            return(myword);  
            break;  
        case'\0':  
            myword->typenum=1000;  
            myword->word="OVER";  
            return(myword);  
            break;  
        default:  
            myword->typenum=-1;  
            myword->word="ERROR";  
            return(myword);  
        }  
}