if (!current.empty()){
        Dependency * temp = current.back();
        if (std::find(this->dependents.begin(), this->dependents.end(),     temp) == this->dependents.end()){
            this->dependents.push_back(temp);    //this is the line the compiler does not like

        }
    }
	
std::vector<Dependency *> dependents;
	
extern std::vector<Dependency *> current;
//this is the definition from the header file. It also resides in a cpp file without extern