At a first look, the preceding implementation looks like recursion, because function add() calls itself, and in a way it is, but it is a compile-time recursion that does not incur any sort of runtime recursion and overhead. The compiler actually generates several functions with a different number of arguments, based on the variadic function template usage, so it is only function overloading that is involved and not any sort of recursion. However, implementation is done as if parameters would be processed in a recursive manner with an end condition.
In the preceding code we can identify the following key parts:
- Typename... Ts is a template parameter pack that indicates a variable number of template type arguments.
- Ts... rest ...
