Question

I’m having problems wrapping my head around this. I have a function

void foo(istream& input) {
     input = cin;
}

This fails (I’m assuming because cin isn’t supposed to be “copyable”.

however, this works

void foo(istream& input) {
    istream& baz = cin;
}

Is there a reason that I can get a reference to cin in baz but I cannot assign it to input?

Thanks

Answer 1

This syntax:

void foo(istream& input) {
     input = cin;
}

Doesn’t create a reference. it invokes the operator= which is meant to copy things around.
This syntax however:

void foo(istream& input) {
    istream& baz = cin;
}

defines a new reference variable.

The key point is that in C++ you can’t change a reference once you’ve declared it.
After the declaration the reference behaves as if it is the object referenced to itself. So using operator= on it tries to copy into it.