Question

Does the C++ standard somehow specify what can a T be in the following declaration:

template <typename T>

I mean, from practical terms of view this can be any particular type, which allows the template to compile (when the corresponding substitution happens).

But what about the strict definition?

Answer 1

It is the responsibility of the programmer to ensure that the data type being used for T is compatible and has all the necessary operations that will performed on T defined. As far as the C++ standard is concerned any data type can be used in place of T there.