Retrieving Function Argument Types in a Variadic Template Class
The specified functor class, Foo, provides a means to invoke functions with arbitrary argument lists. However, determining the argument types within the constructor presents a challenge.
To overcome this, you can utilize the function_traits class as follows:
<code class="cpp">template<typename T> struct function_traits; template<typename R, typename ...Args> struct function_traits<std::function<R(Args...)>> { static const size_t nargs = sizeof...(Args); typedef R result_type; template <size_t i> struct arg { typedef typename std::tuple_element<i, std::tuple<Args...>>::type type; }; };</code>
Within the Foo class, you can employ function_traits to obtain the argument type information:
<code class="cpp">class Foo { std::function<void(ARGS...)> m_f; public: using result_type = typename function_traits<decltype(m_f)>::result_type; using arg0_type = typename function_traits<decltype(m_f)>::arg<0>::type; // ... Additional argument types as needed };</code>
This approach allows you to leverage the type system to access and manipulate the function argument types in a generic and type-safe manner.
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