Can I build a KDTree of pointers to objects?

[Eric Fowler]

I have a toy app that is storing a set<> of pointers to a PlanePoint object,
itself little more than a wrapper for {int x, y;}.

Since I am storing pointers I want to store pointers in my KDTree too. With
that in mind, I wrote this:

//header PlanePoint.h:
class PlanePoint : blah blah ..

inline bool operator==(PlanePoint const * A, PlanePoint const * B);

//header main.cpp:
#include "PlanePoint.h"
typedef KDTree::KDTree<2, PlanePoint*,
std::pointer_to_binary_function<PlanePoint*, int, double> > tree_type_ptr;

When I make I get this:
PlanePoint.h:24: error: 'bool operator==(const PlanePoint*, const
PlanePoint*)' must have an argument of class or enumerated type
PlanePoint.cpp:16: error: 'bool operator==(const PlanePoint*, const
PlanePoint*)' must have an argument of class or enumerated type

This is apparently rooted in some obscure C++  - ism to the effect that you
can't define operators for pointers, or some such thing.

What I want to know is, do we have a workaround? I could just make copies of
my object in the kdtree but would like to avoid that if at all possible.

Thanks

Eric
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