At the moment, it's not possible to compose std::function on top of boost::any because you can't get the interface back out of boost::any. But with a polymorphic_any_cast, you can. Consider the following: template<typename Signature> class function; template<typename Ret, typename... Args> class function<Ret(Args...)> { boost::any contents; struct callable { virtual Ret call(Args... args) = 0; }; template<typename F> struct derived : callable { F f; derived(F obj) : f(std::move(obj)) {} derived(derived&&) = default; derived(const derived&) = default; derived& operator=(derived&&) = default; derived& operator=(const derived&) = default; Ret call(Args... args) { return f(std::forward<Args>(args)...); } }; public: template<typename F> function(F f, /* constraint */ = 0) : contents(derived<F>(std::move(f))) {} function(const function&) = default; function(function&&) = default; function& operator=(const function&) = default; function& operator=(function&&) = default; explicit operator bool() const { return contents; } Ret operator()(Args... args) { if (auto callable = boost::polymorphic_any_cast<callable*>(&contents)) return callable->call(std::forward<Args>(args)...); throw std::bad_function_call(); } }; Here, pretty much all of, well, everything, is just delegated to boost::any. This isn't the entire interface, but enough that you should be able to get the idea. Even on an Itanium ABI system where boost::polymorphic_any_cast can become a dynamic_cast or you assume future Standard support, this won't be as efficient as a specialized std::function implementation, or one based on the more appropriate value_ptr<T>. But the interface offered by polymorphic_any_cast is substantially more flexible than is required here. On 28 November 2013 13:36, Antony Polukhin <antoshkka@gmail.com> wrote:
2013/11/28 Alexander Nasonov <alnsn@yandex.ru>
I'm not *the official* maintainer of the Boost.Any library, I'm just
Antony Polukhin wrote: the
one who made all the latest changes with rvalues and C++11 support. But if there'll be no objections and the official maintainer won't appear I can add this functionality to Boost.Any.
If I'm still the official maintainer I can happily pass my maintainership to Antony.
Thanks! I'll do my best.
-- Best regards, Antony Polukhin
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