Hello, I am attempting to design a class: class C { std::map<double, const A> ma; std::map<double, const B> ma; . public: C(...); }; The keys in the 2 maps are always identical. So I could choose: std::map<double, const std::pair<A,B> > or std::map<double, const std::pair<A,B>* > (ps: AFAIK, using a const-ref for the pair is impossible, but possible with some boost classes) Q1: Is there a difference in memory usage, in access speed or in code readability between the top choice and bottom ones? Q2: Between the 2 bottom ones (storing the pair object in the map vs storing the ptr) Q3: For users of class C, what sort of constructors should I offer? C::C(const std::map<double, const std::pair<A,B>* >& ) Or, should I allow adding elements to the map after the object being constructed? C::add(double, const A&, const B&) Are there better ways with boost classes? Thank you for boost and your time, Rds,