More tk

discuss as desired.
I agree that mapping is an abstract concept. However it does have a canonical (though templated) representation in C++. Following the pattern established by the language spec is reasonable for corresponding concepts and reduces the amount a new user needs to learn.  I like the `Add()` chaining too, but I think it needs to live in (if you pardon the pun) addition to the normal map interface if you are going to call this a map. Your other alternative is to not call it a map (which might have its own baggage).