Call any callable with perfect forwarding

invoke

template <class Fp, class A0, class... Args>
inline auto invoke(Fp&& f, A0&& a0, Args&&... args)
-> decltype((std::forward<A0>(a0).*f)(std::forward<Args>(args)...))
{ return (std::forward<A0>(a0).*f)(std::forward<Args>(args)...); }

template <class Fp, class A0, class... Args>
inline auto invoke(Fp&& f, A0&& a0, Args&&... args)
-> decltype(((*std::forward<A0>(a0)).*f)(std::forward<Args>(args)...))
{ return ((*std::forward<A0>(a0)).*f)(std::forward<Args>(args)...); }

template <class Fp, class A0>
inline auto invoke(Fp&& f, A0&& a0)
-> decltype(std::forward<A0>(a0).*f)
{ return std::forward<A0>(a0).*f; }

template <class Fp, class A0>
inline auto invoke(Fp&& f, A0&& a0)
-> decltype((*std::forward<A0>(a0)).*f)
{ return (*std::forward<A0>(a0)).*f; }

template <class Fp, class... Args>
inline auto invoke(Fp&& f, Args&&... args)
-> decltype(std::forward<Fp>(f)(std::forward<Args>(args)...))
{ return std::forward<Fp>(f)(std::forward<Args>(args)...); }