[Boost-users] ptr_vector sort usage

I can't figure out how to use "sort" method in ptr_vector with the function object. Operator < should be defined, but for various reasons I cant define it in the class A, and I have to do the comparison between the A values using some other values. Example: class A { public: int i; }; class Compare { public: Compare (int i) : _i(i){} //this does not compile, but what's the proper way to define // function object for the sort method in ptr_vector? bool operator<(const A& v1, const A& v2) { return (v1.i > v2.i) &&(_i != 1); } private: int _i; }; ptr_vector<A> lst; Compare cmp(3); lst.sort(cmp);