using void_t = typename make_void<Ts...>::type;
/* A few trait helpers, mainly stolen from libstdc++. Uppercase
- because "and" is a keyword. */
+ because "and/or", etc. are reserved keywords. */
+
+template<typename Predicate>
+struct Not : public std::integral_constant<bool, !Predicate::value>
+{};
+
+template<typename...>
+struct Or;
+
+template<>
+struct Or<> : public std::false_type
+{};
+
+template<typename B1>
+struct Or<B1> : public B1
+{};
+
+template<typename B1, typename B2>
+struct Or<B1, B2>
+ : public std::conditional<B1::value, B1, B2>::type
+{};
+
+template<typename B1,typename B2,typename B3, typename... Bn>
+struct Or<B1, B2, B3, Bn...>
+ : public std::conditional<B1::value, B1, Or<B2, B3, Bn...>>::type
+{};
template<typename...>
struct And;
: public std::conditional<B1::value, And<B2, B3, Bn...>, B1>::type
{};
+/* Concepts-light-like helper to make SFINAE logic easier to read. */
+template<typename Condition>
+using Requires = typename std::enable_if<Condition::value, void>::type;
}
#endif /* COMMON_TRAITS_H */