[IMP-dev] a note on operator>> and operator<<

[Daniel Russel <>]

The correct way to have operator<< and operator>> work for reading and 
writing a class is to declare them as functions in the namespace 
containing the object. Declaring them as member functions does something 
else entirely (or absolutely nothing useful, depending on how you do 
it). The problem is that the compiler searches for operators by checking 
member functions of the left hand object (for i/o it is the stream 
itself), then the current namespace and the namespaces containing the 
arguments. It never looks for member functions of the right hand type.


I suggest implementing operator>> as:

struct Mine {
void show(std::ostream &out=std::cout) const;
};

IMP_OUTPUT_OPERATOR(Mine)