[Boost-users] negating a functor in a remove_copy_if

Hello everyone, I couldn't figure out how to use a logical negation in the following situation. struct IsConditionValid : public unary_function { public: bool operator() (const Event& event)const {} }; remove_copy_if(events.begin(), events.end(), back_inserter(result), IsConditionValid()); <-- how to negate the condition object? What I really need is '! IsConditionValid()'. How can it be done using may be boost::bind ? appreciate your time. thanks pj