Add Traits::None

misc/traits.h

@@ -30,6 +30,11 @@ template <typename... T> struct All : Bool<true> {
 template <typename Head, typename... Tail> struct All<Head, Tail...> : Conditional<Head, All<Tail...>, Bool<false>> {
 };
 
+template <typename... T> struct None : Bool<true> {
+};
+template <typename Head, typename... Tail> struct None<Head, Tail...> : Conditional<Head, Bool<false>, None<Tail...>> {
+};
+
 template <typename... Condition> using EnableIf = typename std::enable_if<All<Condition...>::value, Detail::Enabler>::type;
 template <typename... Condition> using DisableIf = typename std::enable_if<!All<Condition...>::value, Detail::Enabler>::type;
 

tests/traitstests.cpp

@@ -28,6 +28,9 @@ static_assert(!Any<Bool<false>, Bool<false>>::value, "Any: negative case");
 static_assert(Any<Bool<true>, Bool<false>>::value, "Any: positive case");
 static_assert(!All<Bool<true>, Bool<false>>::value, "All: negative case");
 static_assert(All<Bool<true>, Bool<true>>::value, "All: positive case");
+static_assert(!None<Bool<true>, Bool<false>>::value, "None: negative case");
+static_assert(!None<Bool<true>, Bool<true>>::value, "None: negative case");
+static_assert(None<Bool<false>, Bool<false>>::value, "None: positive case");
 
 static_assert(!IsSpecializationOf<string, basic_stringbuf>::value, "IsSpecializationOf: negative case");
 static_assert(IsSpecializationOf<string, basic_string>::value, "IsSpecializationOf: positive case");