C++ 左值表达式

左值表达式可以是变量，指针和引用，所以函数的返回值是这些类型，也能用在赋值号左边。

#include <iostream>
using namespace std;

int x = 10;
int y = 20;

int & refValue(int & x){
	return x;
}

int main(){
	cout << "leftValue before \tx: " << x << '\n';
	refValue(x) = 30;
	cout << "leftValue after \tx: " << x << '\n';
	cout << "-------------------------------\n";
	cout << "leftValue before \ty: " << y << '\n';
	refValue(y) = 40;
	cout << "leftValue after \ty: " << y << '\n';
	return 0;
}