>what would be the difference between a never-null unique_ptr and a reference ? Ownership. > all implementations do use atomic reference counting They do not

>what would be the difference between a never-null unique_ptr and a reference ? Ownership. > all implementations do use atomic reference counting They do not. > exception is the standard way to report errors in C++ Not really, at least in practice. Many C++ developers do not use exceptions at all, with good reason. >turing-complete language can generate arbitrary things and is not immune to halting problem, news at 11 :p The point is that a relatively simple syntax error on behalf of the programmer generates an incomprehensible error message. This is just a comical example of that, and a lot of real world code using templates is full of opaque errors at the start. That said, concepts should help eventually.