编译原理(语法分析源代码).doc

#include<stdio.h>
#include<string.h>
#include<iostream.h>
charprog[80],token[8];
charch;
intsyn,p,m=0,n,sum=0,kk=0;
char*rwtab[6]={"begin","if","then","while","do","end"};
voidexpression();
voidfactor();
voidterm();
voidstatement();
voidyucu();
voidscaner()
{
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;
}
}
elseif((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;
}
elseswitch(ch)
{
case'<':m=0;token[m++]=ch;
ch=prog[p++];
if(ch=='>')
{
syn=21;
token[m++]=ch;
}
elseif(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;
}
}
voidexpression()
{
term();
while(syn==13||syn==14)
{
scaner();
term();
}

return;
}
voidfactor()
{
if(syn==10)
scaner();
elseif(syn==11)
scaner();
elseif(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;

}