Operator() overlading and inheritance in C++ error - c++

Question

here is my problem:
code:
file1.hpp:
namespace Output {
class Stringify{ // base class.....
protected:
size_t prec;
public:
std::stringstream out;
public:
Stringify(const size_t& _p = 5): prec(_p) {out.precision(prec);}
virtual ~Stringify(void){}
public:
std::string operator()(const XYZ& _v){
out.str("");
out << "{ " << _v.x() << ", " << _v.y() << ", " << _v.z() << " }";
return out.str();
}
std::string operator()(const XYZ& _v, const bool& _status){
out << "{ " << _v.x() << ", " << _v.y() << ", " << _v.z() << " }";
return out.str();
}
};
}
where XYZ is a vector object.
file2.hpp:
namespace NODE {
class Stringify: public Output::Stringify {
public:
Stringify2(const size_t& _p = 5): Output::Stringify(_p) {}
virtual ~Stringify2(void){}
public:
std::string operator()(const VERTEX& _obj){ return "What?";}
};
}
where VERTEX is another object with members values of type XYZ
main.cpp:
int main(int argc,char * argv[]){
XYZ v(1,2,3);
NODE::Stringify printer;
cout << printer(v) << endl;
return 0;
}
output is:
What?
when it should:
be {1,2,3}
Compilation is ok but,
As far as I know, NODE::Stringify is able to print {1,2,3}, because of, his base object
has inherit the method for XYZ argument, but it prints the Method with the arguments
of VERTEX (What?). virtual word is not neccesary, because I do not overwrite a method in
the base class.
As a information: I am compiling in MAC OS 10.8 with llvm-gcc-4.2
using Eigen 3.0 libs (typedef Eigen::vector3d XYZ)
Any idea?
Thanks in advance.

Answer 1

Your operator () in the derived class hides the operator () overloads from the base class (which you name Stringify in your example, but that's probably a typo, since the constructor and destructor are named (~)Stringify2).
You can fix this through a using declaration inside the derived class:
namespace NODE {
class Stringify2 : public Output::Stringify {
// ^
public:
using Output::Stringify::operator ();
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
// This should fix the problem
Stringify2(const size_t& _p = 5): Output::Stringify(_p) {}
virtual ~Stringify2(void){}
public:
std::string operator()(const VERTEX& _obj){ return "What?";}
};
}