《编译原理》 实验报告
第二篇：编译原理(语法分析源代码)
#include＜stdio.h＞
#include＜string.h＞
#include＜iostream.h＞
char prog[80],token[8];
char ch;
int syn,p,m=0,n,sum=0,kk=0;
char *rwtab[6]={"begin","if","then","while","do","end"};
void expression();
void factor();
void term();
void statement();
void yucu();
void scaner()
{
for(n=0;n＜8;n++) token[n]=NULL;
ch=prog[p++];
while(ch==' ')
{
ch=prog[p];
p++;
}
if((ch＞='a'&&ch＜='z')||(ch＞='A'&&ch＜='Z'))
{
m=0;
while((ch＞='0'&&ch＜='9')||(ch＞='a'&&ch＜='z')||(ch＞='A'&&ch＜='Z'))
{
token[m++]=ch;
ch=prog[p++];
}
token[m++]='\0';
p--;
syn=10;
for(n=0;n＜6;n++)
if(strcmp(token,rwtab[n])==0)
{
syn=n+1;
break;
}
}
else if((ch＞='0'&&ch＜='9'))
{
{
sum=0;
while((ch＞='0'&&ch＜='9'))
{
sum=sum*10+ch-'0';
ch=prog[p++];
}
}
p--;
syn=11;
if(sum＞32767)
syn=-1;
}
else switch(ch)
{
case'＜':m=0;token[m++]=ch;
ch=prog[p++];
if(ch=='＞')
{
syn=21;
token[m++]=ch;
}
else if(ch=='=')
{
syn=22;
token[m++]=ch;
}
else
{
syn=23;
p--;
}
break;
case'＞':m=0;token[m++]=ch;
ch=prog[p++];
if(ch=='=')
{
syn=24;
token[m++]=ch;
}
else
{
syn=20;
p--;
}
break;
case':':m=0;token[m++]=ch;
ch=prog[p++];
if(ch=='=')
{
syn=18;
token[m++]=ch;
}
else
{
syn=17;
p--;
}
break;
case'*':syn=15;token[0]=ch;break;
case'/':syn=16;token[0]=ch;break;
case'+':syn=13;token[0]=ch;break;
case'-':syn=14;token[0]=ch;break;
case'=':syn=25;token[0]=ch;break;
case';':syn=26;token[0]=ch;break;
case'(':syn=27;token[0]=ch;break;
case')':syn=28;token[0]=ch;break;
case'#':syn=0;token[0]=ch;break;
case'\n':syn=-2;break;
default: syn=-1;break;
}
}
void expression()
{
term();
while(syn==13||syn==14)
{
scaner();
term();
}
return;
}
void factor()
{
if(syn==10)
scaner();
else if(syn==11)
scaner();
else if(syn==27)
{
scaner();
expression();
if(syn==28)
{
scaner();
}
else
{
cout＜＜"输出')'错误"＜＜endl;
kk=1;
}
}
else
{
cout＜＜"表达式错误"＜＜endl;
kk=1;
}
return;
}
void term()
{
factor();
while(syn==15||syn==16)
{
scaner();
factor();
}
return;
}
void statement()
{
if(syn==10)
{
scaner();
if(syn==18)
{
scaner();
expression();
}
else
{
cout＜＜"赋值号错误"＜＜endl;
kk=1;
}
}
else
{
cout＜＜"语句错误"＜＜endl;
kk=1;
}
return;
}
void yucu()
{
statement();
while(syn==26)
{
scaner();
statement();
}
return;
}
void lrparser()
{
if(syn==1)
{
scaner();
yucu();
if(syn==6)
{
scaner();
if(syn==0&&(kk==0))
{
cout＜＜"success"＜＜endl;
}
}
else if(kk!=1)
{
cout＜＜"缺少end错误"＜＜endl;
}
}
else
{
cout＜＜"缺少begin错误"＜＜endl;
}
return;
}
void main()
{
p=0;
cout＜＜"Please input string:"＜＜endl;
do
{
cin.get(ch);
prog[p++]=ch;
}
while(ch!='#');
p=0;
scaner();
lrparser();
}