I'm working on what is probably a complicated solution to a relatively trivial
problem.  I have no idea whether I'm doing this right or not (well, obviously,
I'm doing -something- wrong) but based on everything I've read, and all of the
examples I could dig up, I don't see anything wrong with my structure.

basically, I have a custom library:

#ifndef _MY_LIB_
#define _MY_LIB_
#include <iostream>
#include <cmath>
using std::ostream;

namespace geometry {

    enum pointName{X,Y,Z};

    class point3d
    {
        public:
        .
        .
        .
        friend ostream &operator <<(ostream &, const point3d &);

        private:
    };

    class vector3d : public point3d
    {
        ...
    };

    const point3d ORIGIN;
    const vector3d ZERO_VECTOR;
}

class implementations are handled in separate files, and compiled with:

g++ -g -c -Wall -std=c++0x point3d.cpp vector3d.cpp

This compiles fine, and everything is awesome until I try to use the << operator
in my unit test program.  g++ gives me the following:

g++ -g -Wall -o uTest unit_test.cpp point3d.o vector3d.o
/tmp/cca86ida.o: In function `point_arithmetic_test()':
/home/.../Documents/Projects/Planets/unit_test.cpp:56:
undefined reference to `geometry::operator<<(std::basic_ostream<char,
std::char_traits<char> >&, geometry::point3d const&)'
/home/.../Documents/Projects/Planets/unit_test.cpp:57:
undefined reference to `geometry::operator<<(std::basic_ostream<char,
std::char_traits<char> >&, geometry::point3d const&)'
collect2: ld returned 1 exit status
make: *** [uTest] Error 1

now unit_test.cpp, like both of my library files uses:

using namespace geometry;

if I remove the namespace wrapper from around my classes, everything works.

can somebody tell me what I'm missing?

Regards,
A.D.B.

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