Using a reference in a conditional statement...

I was looking at some code that uses fstream:


    #include <fstream>
    //
    // which includes:
    // istream& getline( char* buffer, streamsize num );
    //

    ifstream fin;
    while( fin.getline(line, size) ) {
        ...
    }


If fin.getline() returns a reference, how could it be used in a
conditional
statement?  I've looked at the member functions and I could not find a
conversion to a bool type.