引用问题

#include <iostream>
using namespace std;
int f(int i)
{
return i++;
}

int g(int& i)
{
return i++;
}

int main()
{
int a = 0, b = 0, c = 0, d = 0;

int p, q;

a += f(g(a));

f(5); // work
// g(5); // does not work. A reference needs a LValue, but 5 is an RValue

/**
A refernce is a LValue, which should in general be associated with
a named storage.

g(b) is a RValue.
*/
p=g(b);
b+=g(p);
//b += g(g(b)); //请问这个是什么问题呢？提示是不能FROM‘INT’TO‘INT&’

q =f(c);
c+= g(q);
//c += g(f(c)); //这个错误同上，应该怎样该才对呢？
d += f(f(d));
cout << "a=" << a << "b=" << b << "c=" << "d=" << d << "\n";

return 1;
}