If you bundle functions and data, you end up implementing M functions each on N types, or M*N. If you can separate your functions and your data, you implement M

If you bundle functions and data, you end up implementing M functions each on N types, or M*N. If you can separate your functions and your data, you implement M functions and N types, or M+N. This is an explicit design goal of the STL and Stepanov's research that led to it. Similarly, Stepanov was explicitly trying to be able to write a polymorphic max function `T max(T a, T b)`. That is, the instance of the max function actually used is chosen based on all the arguments, not solely on the first, which is the definition of multiple dispatch. C++ also has a single dispatch object system, and the STL even mixes them, putting things like vector::push on the class with the single dispatch system and the STL algorithms in the multiple dispatch system.