Stack operation: Reverse Polish expression calculation

char Calval_InvertPoland(char Buffer[]){
	InitStack(S);
	int i = 0;	ElemType c, e1, e2;    //定义操作符，运算数值
	while(Buffer[i]!="#"){    //对数组中逆波兰表达式元素计算
        //如果当前元素是数字则入栈
		if((Buffer[i]!="+")||(Buffer[i]!="-")||(Buffer[i]!="*")||(Buffer[i]!="/")){
			Push(S,Buffer[i]);
		}else{    
        //遇到操作符则取出栈顶的两个元素进行该操作符的运算，处理结果入栈进行下一轮的计算
			if(!IsEmpty(S)){
				Pop(S,e1);
				Pop(S,e2);
				c = Cal(e1,e2,Buffer[i]);
				Push(S,c);
			}
		}
		i++;
	}
}
ElemType Cal(ElemType e1, ElemType e2, char opt){
	ElemType x;
	switch(opt){
		case '+':
			x = e1+e2;
			break;
		case '-':
			x = e1-e2;
			break;
		case '*':
			x = e1*e2;
			break;
		case '/':
			x = e1/e2;
			break;
		default:
			break;
	}
	return x;
}