yuyifenxi.cpp

语义分析：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

#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "iostream.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();
void yucu();
char *term();
void statement();
void lrparser();
char *newtemp();
void scaner();
void emit(char *result,char *ag1,char *op,char *ag2);
void main()
{ 
	int j;
	q=p=kk=0;
	printf("\n请输入一个句子并以#结束: ");
    do
   { 
		scanf("%c",&ch);
    
		prog[p++]=ch;
   
	}while(ch!='#');
    p=0;
    scaner();
    lrparser();
    if(q>19)
		cout<<"句子太长!!!\n";
    else 
		for (j=0;j<q;j++)
			cout<<quad[j].result1<<"="<<quad[j].ag11<<quad[j].op1<<quad[j].ag21<<endl;;
}
void lrparser()
{ 

    kk=0;
    if(syn==1)      
	{ 
		scaner();
		yucu();
		if(syn==6)
		{ 	
			scaner();		
			if((syn==0)&&(kk==0))  
				printf("Success!\n");
		}
  	else 
		{ 		
			if(kk!=1)
				printf("缺少'end' !\n");       			
			kk=1;
			exit(0);	
		}	
	}
    else
	{
		cout<<"缺少begin!\n";
		kk=1;   
		exit(0);
	}
}
void yucu()
{ 
	statement(); 
	while(syn==26)
	{ 
		scaner();
        statement();
   }
}
void statement()
{ 
	char tt[8],eplace[8]; 
    if (syn==10)
	{ 
		strcpy(tt,token);
		scaner();     
		if(syn==18)
   		{
			scaner();	
			strcpy(eplace,expression());
			emit(tt,eplace,"","");
		}    	 
		else 
	 	{ 		 
			printf("缺少 ':=' !\n");     
			kk=1;	
			exit(0);    
		}	
	}
}
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;
				exit(0);
				}
			}
			else 
			{ 
				printf("error on '(' !\n");
				kk=1;
				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);
}
void 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;
       }
}
void 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++;
}