I have some template functions to aggregate a vector into a string in my C++ project. And I need to pass aggregation algorithm from one function to another using std::function.

I haven arbitrary type T that specializes std::numeric_limits. Typically, for standard types that have the concept of a zero-element, std::numeric_limits<T>::zero() would make sense, but as we know, std::numeric_limits doesn’t provide such a member function.