Type trait to check that all types in a parameter pack are copy constructible

Question

I need a type trait to check whether all types in a parameter pack are copy constructible. This is what I\'ve done so far. The main function contains some test cases, to che

Answer 1

First define a reusable utility to test whether every predicate in a pack is true:

template
  struct and_
  : std::true_type
  { };

template
  struct and_
  : std::conditional, std::false_type>::type
  { };

Then it's trivial to use that with is_copy_constructible (or any other unary type trait):

template
  using areCopyConstructible = and_...>;

One advantage of defining and_ like this is that it short-circuits, i.e. stops instantiating is_copy_constructible for the rest of the pack after the first false result.