编译原理语义分析

来源：互联网发布：mcabook软件关不掉编辑：程序博客网时间：2024/05/21 22:52

#include<stdio.h>
#includ<string.h>
char prog[100],token[8],ch;
char *rwtab[6]={"begin","if","then","while","do","end"};
int syn,p,m,n,sum,q,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 '#'):");
do
    {
    scanf("%c",&ch);
    prog[p++]=ch;
    }while(ch!='#');
    p=0;
    scaner();
    lrparser();
    if(q>19)
    printf("to long sentence!\n");
    else
    for(j=0;j<q;j++)
    printf("%s= %s %s %s \n\n",quad[j].result1,quad[j].ag11,quad[j].op1,quad[j].ag21);
    getch();
}//main

int lrparser()
{
int schain=0;
kk=0;
if(syn==1)
    {
    scaner();
    schain=yucu();//为什么不直接调用,这样有何作用呢？
    if(syn==6)
        {
        scaner();
        if((syn==0)&&(kk==0))
        printf("success!\n");
        }
        else
        {
        if(kk!=1)
        printf("short of 'end'! \n");//达不到
        kk=1;
        getchar();
        exit(0);
        }
    }
    else
    {
    printf("short of 'begin'!\n");
    kk=1;
    getchar();
    exit(0);
    }
    return(schain);
}//lrparser

int yucu()
{
int schain=0;
schain=statement();
while(syn==26)
{
  scaner();
  schain=statement();
}
return(schain);
}//yucu
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);
    }
}//statement
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))//jia jian
    {
    if(syn==13)
    strcpy(tt,"+");
    scaner();
    strcpy(ep2,term());
    strcpy(tp,newtemp());
    emit(tp,eplace,tt,ep2);
    strcpy(eplace,tp);
    }
    return(eplace);
}//expression

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);
}//term

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();//括号里面的加减
     if(syn==28)
     scaner();
     else
     {
       printf("error on')'!\n");
       kk=1;
       getch();
       exit(0);
     }
     }
        else
        {
        printf("error on'('!\n");
        kk=1;
        getchar();
        exit(0);
        }
        return(fplace);
}//factor

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);
}//newtemp

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;
     }
  }//scaner
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++;
}//emit