TypeTraits.hpp

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#pragma once
#include <type_traits> 
#include <tuple>
#include <cstddef>
 
template<typename T, typename B>
struct is_derived_from: std::integral_constant<bool, std::is_base_of<B, T>::value> {};
 
template<typename Base, typename... Derived>
struct all_derived;
 
template<typename Base> // (Base),  n = 0
struct all_derived<Base> : std::true_type {};
 
template<typename Base, typename First, typename... Rest> // (Base, {Item₀, …, Itemₙ}),  n ≥ 0
struct all_derived<Base, First, Rest...> :
    std::integral_constant<bool, //use as a type
        std::is_base_of<Base, First>::value // is_base_of
        && all_derived<Base, Rest...>::value> {}; // recursive
 
template <typename T>
struct is_tuple : std::false_type {};
 
template <typename... Args>
struct is_tuple<std::tuple<Args...>> : std::true_type {};
 
 
template <std::size_t... I>
struct index_sequence {};
 
template <std::size_t N, std::size_t... I>
struct make_index_sequence_impl : make_index_sequence_impl<N - 1, N - 1, I...> {};
 
template <std::size_t... I>
struct make_index_sequence_impl<0, I...> {
    typedef index_sequence<I...> type;
};