MetafunctionDescriptionA metafunction is a class or a class template that represents a function invocable at compile-time. An non-nullary metafunction is invoked by instantiating the class template with particular template parameters (metafunction arguments); the result of the metafunction application is accessible through the instantiation's nested type typedef. All metafunction's arguments must be types (i.e. only type template parameters are allowed). A metafunction can have a variable number of parameters. A nullary metafunction is represented as a (template) class with a nested type typename member. Expression requirementsIn the following table and subsequent specifications, f is a Metafunction.
Expression semanticstypedef f::type x;
typedef f<>::type x;
typedef f<a1,... an>::type x;
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