cpp implementation of constexpr fold

fold_ver2.cpp

#include <iostream>

template <typename F>
struct Fold {
    F func;

    template <typename Fs>
    constexpr Fold(Fs&& func) : func(std::forward<Fs>(func)) {}

    template <typename T, typename U>
    constexpr auto impl(T&& arg1, U&& arg2) {
        return func(std::forward<T>(arg1), std::forward<U>(arg2));
    }

    template <typename T, typename... Ts>
    constexpr auto impl(T&& init, Ts&&... rest) {
        return func(std::forward<T>(init), impl(std::forward<Ts>(rest)...));
    }

    template <typename... Ts>
    constexpr auto operator()(Ts&&... args) {
        return impl(std::forward<Ts>(args)...);
    }
};

template <typename F>
constexpr auto fold(F&& func) {
    return Fold<F>(std::forward<F>(func));
}

int main() {
    auto max = [](auto a, auto b) constexpr { return a > b ? a : b; };
    constexpr int result = fold(max)(1, 4, 3, 5, 2);
    std::cout << result << std::endl;
}