做这些事情的正确方法是什么？
我想在参数包上使用条件，例如：
static_assert(all_of<ChildTypes ...>::are_in<ParentTypes ...>::value);
简而言之，我有这样的代码：
template <class ... Types> struct is_in
{
template <class Arg>
struct test : any_of<Types ...>::is_same_as<Arg> {}; // error C2059
};
template <class ... Args>
struct all_of
{
template <class ... Types>
struct are_in : all_fulfill<typename is_in<Types ...>::test, Args ...> {};
template <class Type>
struct are : all_fulfill<typename is_same_as<Type>::test, Args ...> {};
};
any_of<Types...>::is_same_as<Type>::valueall_of<Types...>::are<Type>::valueall_fulfill尝试调用 are_in 时出现以下错误：
error C2059: syntax error: '<'
error C2039: 'value': is not a member of 'is_in<bool,int>::test<Head>' with [ Head=int ]
error C2065: 'value': undeclared identifier
error C2975: '_Test': invalid template argument for 'std::conditional', expected compile-time constant expression
作为背景：
template < template <class> typename Test, typename... List >
struct all_fulfill : std::false_type {};
template < template <class> typename Test, typename Head, typename... List >
struct all_fulfill<Test, Head, List ...>
: std::conditional< Test<Head>::value, // error C2065 // error C2975
all_fulfill<Test, List...>, // error C2039
std::false_type
>::type {};
template < template <class> typename Test >
struct all_fulfill<Test> : std::true_type {};
试过：
在
struct is_inusing AnyOfTypes = any_of<Types ...>;struct AnyOfTypes : any_of<Types ...> {}预期结果：
any_of<Types...>::is_same_as<Type>::value