1.cpp

实验目的 通过上机实习,加深对语法制导翻译原理的理解,掌握将语法分析所识别的语法成分变换为中间代码的语义翻译方法. 实验要求 采用递归下降语法制导翻译法,对算术表达式、赋值语句进行语义分析并生成

#include "stdio.h"
#include "string.h"
#include "stdlib.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 '#'): ");
do
   { scanf("%c",&ch);
     prog[p++]=ch;
   }while(ch!='#');
p=0;
scaner();
lrparser();
if(q>19)printf(" to long sentense!\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();
}
int lrparser()
{ int schain=0;
    kk=0;
    if (syn==1)
      { scaner();
schain=yucu();
if(syn==6)
{ scaner();
    if((syn==0)&&(kk==0)) printf("Success!\n");
}
else { if(kk!=1)printf("short of 'end' !\n");
        kk=1;
//        getch();
        exit(0);
      }
      }
    else { printf("short of 'begin' !\n");
    kk=1;
//    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");
     kk=1;
//   getch();
     exit(0);
   }
   }
else { printf("error on '(' !\n");
kk=1;
// 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);
}
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;
       }
    }
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++;
}