yuyi.c

编译原理实验语义分析源程序

#include "stdio.h"
#include "string.h"

char prog[100],token[8],ch;
char *rwtab[6]={"begin","if","then","while","do","end"};
int syn,p,m,n,sum,q;
int kk;

struct
{
    char result1[8];
    char ag11[8];
    char op1[8];
    char ag21[8];
}quad[20];

char *factor();
char *expression();
int yucu();
char *term();
int statement();
int lrparser();
char *newtemp();

scaner();
emit(char *result,char *ag1,char *op,char *ag2);

main()
{
    int j;
    q=p=kk=0;
    printf("\nplease input a string (end with '#'):\n\n ");
    do
    {
        scanf("%c",&ch);
        prog[p++]=ch;
    }while(ch!='#');
    p=0;

    scaner();
    lrparser();

    for (j=0;j<q;j++)
        printf("\n%s = %s %s %s \n",quad[j].result1,quad[j].ag11,quad[j].op1,quad[j].ag21);
    getch();
}

int lrparser()
{
    int schain=0;
    kk=0;
    if (syn==1)
    {
        scaner();
        schain=yucu();
        if(syn==6)
        {
            scaner();
            if(syn==0)  printf("\nSuccess!\n");
        }
        else
        {
            printf("\nshort of 'end' !\n");

            getch();
            exit(0);
        }
    }
    else
    {
        printf("\nshort of 'begin' !\n");

        getch();
        exit(0);
    }
    return (schain);
}


int yucu()
{
    int schain=0;
    schain=statement();
    while(syn==26)
    {
        scaner();
        schain=statement();
    }
    return (schain);
}


int statement()
{
    char tt[8],eplace[8];
    int schain=0;
    if (syn==10)
    {
        strcpy(tt,token);
        scaner();
        if(syn==18)
        {
            scaner();
            strcpy(eplace,expression());
            emit(tt,eplace,"","");
            schain=0;
        }
        else
        {
            printf("short of sign ':=' !\n");
            kk=1;
            getch();
            exit(0);
        }
        return (schain);
    }
}

char *expression()
{
    char *tp,*ep2,*eplace,*tt;
    tp=(char *)malloc(12);
    ep2=(char *)malloc(12);
    eplace=(char *)malloc(12);
    tt=(char *)malloc(12);
    strcpy(eplace,term());
    while((syn==13)||(syn==14))
    {
        if (syn==13)strcpy(tt,"+");
        else strcpy(tt,"-");
        scaner();
        strcpy(ep2,term());
        strcpy(tp,newtemp());
        emit(tp,eplace,tt,ep2);
        strcpy(eplace,tp);
    }
    return (eplace);
}


char *term()
{
    char *tp,*ep2,*eplace,*tt;
    tp=(char *)malloc(12);
    ep2=(char *)malloc(12);
    eplace=(char *)malloc(12);
    tt=(char *)malloc(12);
    strcpy(eplace,factor());
    while((syn==15)||(syn==16))
    {
        if (syn==15)strcpy(tt,"*");
        else strcpy(tt,"/");
        scaner();
        strcpy(ep2,factor());
        strcpy(tp,newtemp());
        emit(tp,eplace,tt,ep2);
        strcpy(eplace,tp);
    }
    return (eplace);
}

char *factor()
{
    char *fplace;
    fplace=(char *)malloc(12);
    strcpy(fplace,"");
    if(syn==10)
    {
        strcpy(fplace,token);
        scaner();
    }
    else if(syn==11)
    {
        itoa(sum,fplace,10);
        scaner();
    }
    else if(syn==27)
    {
        scaner();
        fplace=expression();
        if(syn==28) scaner();
        else
        {
            printf("error on ')' !\n");

            getch();
            exit(0);
        }
    }
    else
    {
        printf("error on '(' !\n");

        getch();
        exit(0);
    }
    return (fplace);
}


char *newtemp()
{
    char *p;
    char m[8];
    p=(char *)malloc(8);
    kk++;
    itoa(kk,m,10);
    strcpy(p+1,m);
    p[0]='t';
    return(p);
}

emit(char *result,char *ag1,char *op,char *ag2)
{ 
    strcpy(quad[q].result1,result);
    strcpy(quad[q].ag11,ag1);
    strcpy(quad[q].op1,op);
    strcpy(quad[q].ag21,ag2);
    q++;
}


scaner()
{   sum=0;
    for(m=0;m<8;m++)token[m++]=NULL;
    m=0;
    ch=prog[p++];
    while(ch==' ')ch=prog[p++];
    if(((ch<='z')&&(ch>='a'))||((ch<='Z')&&(ch>='A')))
    { 
        while(((ch<='z')&&(ch>='a'))||((ch<='Z')&&(ch>='A'))||((ch>='0')&&(ch<='9')))
        {
            token[m++]=ch;
            ch=prog[p++];
        }
        p--;
        syn=10;
        token[m++]='\0';
        for(n=0;n<6;n++)
        if(strcmp(token,rwtab[n])==0)
        { 
            syn=n+1;
            break;
        }
    }
    else if((ch>='0')&&(ch<='9'))
    { 
        while((ch>='0')&&(ch<='9'))
        { 
            sum=sum*10+ch-'0';
            ch=prog[p++];
        }
        p--;
        syn=11;
    }
    else switch(ch)
    {  
        case '<':
        m=0;
        ch=prog[p++];
        if(ch=='>') syn=21;
        else if(ch=='=') syn=22;
        else
        { 
            syn=20;
            p--;
        }
        break;

        case '>':
        m=0;
        ch=prog[p++];
        if(ch=='=') syn=24;
        else
        { 
            syn=23;
            p--;
        }
        break;

        case ':':
        m=0;
        ch=prog[p++];
        if(ch=='=') syn=18;
        else
        { 
            syn=17;
            p--;
        }
        break;
        case '+': syn=13; break;
        case '-': syn=14; break;
        case '*': syn=15; break;
        case '/': syn=16; break;
        case '(': syn=27; break;
        case ')': syn=28; break;
        case '=': syn=25; break;
        case ';': syn=26; break;
        case '#': syn=0; break;
        default: syn=-1;break;
    }
}