How does the “return value” of operator >> of istream class work?

Question

I tried to understand the statement:

    int main() {
        fstream inf( \"ex.txt\", ios::in );
        char c;
        while( inf >> c ) {
                  


        

Answer 1

What does ( inf >> c ) return in the while loop above?

void*. The loop test resolves to while (inf.operator void*() != NULL).

How does a reference can be evaluated as true or false?

But supporting conversion to bool or something convertible to bool.

How does the internal implementation of istream actually work?

It just returns a reference to itself (return *this) so it can support chaining.