编译原理 之 语法分析器（自上而下分析法）

#include <stdio.h>
#include <stdlib.h>
#include <windows.h>

#define fprint(fpw,k) { if(k>='a'&&k<='z') fprintf(fpw,"%c",k); else fprintf(fpw,"temp%d",k); }

int PLACE=1;
int index=1;

typedef struct _info{
int place;
int op;
}info;

int advance(FILE *fpr)
{
char t;
t=fgetc(fpr);
if(t==EOF)
return '#';
return t;
}

int E(FILE *fpr,FILE *fpw,int *character,info *k);
int V(FILE *fpr,FILE *fpw,int *character,info *k)
{
int flag=0;
if(*character>='a'&&*character<='z')
flag=1;
if(flag==0)
{
printf("error in V!\n");
return 0;
}
k->place=*character;
*character=advance(fpr);
return 1;
}

int F(FILE *fpr,FILE *fpw,int *character,info *k)//F=(E)|V
{
info v;
v.place=0;
if(*character=='(')
{
*character=advance(fpr);
if(E(fpr,fpw,character,&v)==0)
return 0;
if(*character!=')')
{
printf("error in F!\n");
return 0;
}
*character=advance(fpr);
}
else
{
if(V(fpr,fpw,character,&v)==0)
return 0;;

}
k->place=v.place;
return 1;
}

int T1(FILE *fpr,FILE *fpw,int *character,info *k)// T1=(*|/)F T1
{
info f,t1;
f.place=t1.place=0;
if(*character=='*'||*character=='/')
{
if(*character=='*')
k->op=0;
else
k->op=1;
*character=advance(fpr);
if(F(fpr,fpw,character,&f)==0)
return 0;
if(T1(fpr,fpw,character,&t1)==0)
return 0;
if(t1.place==0)
k->place=f.place;
else
{
k->place=PLACE++;
fprintf(fpw,"%3d: ",index++);
fprintf(fpw,"'%c',",t1.op==0?'*':'/');
fprint(fpw,f.place);
fprintf(fpw,",");
fprint(fpw,t1.place);
fprintf(fpw,",");
fprint(fpw,k->place);
fprintf(fpw,"\n");
}
}
return 1;
}

int T(FILE *fpr,FILE *fpw,int *character,info *k)// T=F T1
{
info f,t1;
f.place=t1.place=0;
if(F(fpr,fpw,character,&f)==0)
return 0;
if(T1(fpr,fpw,character,&t1)==0)
return 0;
if(t1.place==0)
k->place=f.place;
else
{
k->place=PLACE++;
fprintf(fpw,"%3d: ",index++);
fprintf(fpw,"'%c',",t1.op==0?'*':'/');
fprint(fpw,f.place);
fprintf(fpw,",");
fprint(fpw,t1.place);
fprintf(fpw,",");
fprint(fpw,k->place);
fprintf(fpw,"\n");
}
return 1;
}

int E1(FILE *fpr,FILE *fpw,int *character,info *k)// E1=(+|-)T E1
{
info t,e1;
t.place=e1.place=0;
if(*character=='+'||*character=='-')
{
if(*character=='+')
k->op=0;
else
k->op=1;
*character=advance(fpr);
if(T(fpr,fpw,character,&t)==0)
return 0;
if(E1(fpr,fpw,character,&e1)==0)
return 0;
if(e1.place==0)
k->place=t.place;
else
{
k->place=PLACE++;
fprintf(fpw,"%3d: ",index++);
fprintf(fpw,"'%c',",e1.op==0?'+':'-');
fprint(fpw,t.place);
fprintf(fpw,",");
fprint(fpw,e1.place);
fprintf(fpw,",");
fprint(fpw,k->place);
fprintf(fpw,"\n");
}
}
return 1;
}

int E(FILE *fpr,FILE *fpw,int *character,info *k)// E=T E1
{
info t,e1;
t.place=e1.place=0;
if(T(fpr,fpw,character,&t)==0)
return 0;
if(E1(fpr,fpw,character,&e1)==0)
return 0;
if(e1.place==0)
k->place=t.place;
else
{
k->place=PLACE++;
fprintf(fpw,"%3d: ",index++);
fprintf(fpw,"'%c',",e1.op==0?'+':'-');
fprint(fpw,t.place);
fprintf(fpw,",");
fprint(fpw,e1.place);
fprintf(fpw,",");
fprint(fpw,k->place);
fprintf(fpw,"\n");
}
return 1;
}

int A(FILE *fpr,FILE *fpw,int *character)// V=E
{
info e,v;
e.place=v.place=0;
if(V(fpr,fpw,character,&v)==0)
return 0;
if(*character!='=')
{
printf("error in A!\n");
return 0;
}
*character=advance(fpr);
if(E(fpr,fpw,character,&e)==0)
return 0;
fprintf(fpw,"%3d: ",index++);
fprintf(fpw,"'=',");
fprint(fpw,e.place);
fprintf(fpw,",-,");
fprint(fpw,v.place);
fprintf(fpw,"\n");
return 1;
}

void scan(FILE *fpr,FILE *fpw)
{
int character;
index=1;
PLACE=1;
character=advance(fpr);
if(A(fpr,fpw,&character)==0)
return;
printf("succeed!\n");
}

int main()
{
int n;
system("color 1E");
FILE *fpr,*fpw;
char filepath[256];
while(1)
{
printf("选择文件输入的请按 1，结束请 2！\n");
scanf("%d",&n);
switch(n)
{
case 1:
{
A: printf("请输入源文件路径: ");
scanf("%s",filepath);
fpr=fopen(filepath,"rt");
if(fpr==NULL)
{
printf("打开源文件失败!\n");
goto A;
}
putchar(10);
B:printf("请输入输出文件路径: ");
scanf("%s",filepath);
fpw=fopen(filepath,"wt");
putchar(10);
if(fpw==NULL)
{
printf("创建目标文件失败!\n");
goto B;
}
scan(fpr,fpw);
fclose(fpr);
fclose(fpw);
fpw=fopen(filepath,"rt");
char ch;
while(!feof(fpw))
{
ch=fgetc(fpw);
printf("%c",ch);
}
fclose(fpw);
break;
}

case 2:
{
printf("谢谢使用！\n\n\n");
system("pause");
return 0;
}
default: printf("输入数字错误，请重新输入数字：！\n\n\n");
}
}
return 0;
}