c++ - Can I use template aliases as template template parameters?

Question

Can I use template aliases as template template parameters?

template <template <typename...> class> struct foo {};

template <typename T> using simple_ptr = std::unique_ptr<T>;

foo<std::unique_ptr> a; // this doesn't work, std::unique_ptr has two parameters
foo<simple_ptr> b; // does this work?

question from:https://stackoverflow.com/questions/7319567/can-i-use-template-aliases-as-template-template-parameters

Answer 1

Yes, it is apparently allowed. According to the latest draft of the upcoming standard I could find, it is stated that

A template-argument for a template template-parameter shall be the name of a class template or an alias template [...].

However, alias templates seems very seldomly supported at the moment, so you might have some trouble making it work with most compilers.