switch语句不被执行.....

typedef char OptrType;
.
.
.
char Precede(OptrType optr,char c){
//算符优先级比较
char relationship;
//the code used for comparing
char a=optr;
char b=c;

if(a=='+'||a=='-'){
if(b!='+'&&b!='-'&&b!='#')relationship='<';
else relationship='>';
}
if(a=='*'||a=='/'){
if(b!='(')relationship='<';
else relationship='>';
}
if(a=='('){
if(b==')')relationship='=';
if(b=='#')exit(0);
else relationship='<';
}
if(a==')'){
if(b=='(')exit(0);
else relationship='>';
}
if(a=='#'){
if(b==')')exit(0);
if(b=='#')relationship='=';
else relationship='<';
}
return relationship;
}//precede()结束

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