std::experimental::disjunction(3)

NAME
std::experimental::disjunction - std::experimental::disjunction

Synopsis
   Defined in header <experimental/type_traits>
   template<class... B> (library fundamentals TS v2)
   struct disjunction;
   Forms the logical disjunction of the type traits B..., effectively performing a
   logical or on the sequence of traits.
   The specialization std::experimental::disjunction<B1, ..., BN> has a public and
   unambiguous base that is
     * if sizeof...(B) == 0, std::false_type; otherwise
     * the first type Bi in B1, ..., BN for which bool(Bi::value) == true, or BN if
       there is no such type.
   The member names of the base class, other than disjunction and operator=, are not
   hidden and are unambiguously available in disjunction.
   Disjunction is short-circuiting: if there is a template type argument Bi with
   bool(Bi::value) != false, then instantiating disjunction<B1, ..., BN>::value does
   not require the instantiation of Bj::value for j > i

Template parameters
   B... - every template argument Bi for which Bi::value is instantiated must be usable
          as a base class and define member value that is convertible to bool
  Helper variable template
   template<class... B>
   constexpr bool disjunction_v = (library fundamentals TS v2)
   disjunction<B...>::value;

Possible implementation
   template<class...> struct disjunction : std::false_type { };
   template<class B1> struct disjunction<B1> : B1 { };
   template<class B1, class... Bn>
   struct disjunction<B1, Bn...>
       : std::conditional_t<bool(B1::value), B1, disjunction<Bn...>> { };

Notes
   A specialization of disjunction does not necessarily inherit from of either
   std::true_type or std::false_type: it simply inherits from the first B whose
   ::value, explicitly converted to bool, is true, or from the very last B when all of
   them convert to false. For example, disjunction<std::integral_constant<int, 2>,
   std::integral_constant<int, 4>>::value is 2.

Example
    This section is incomplete
    Reason: no example

See also
   disjunction variadic logical OR metafunction
   (C++17) (class template)