Jul 21, 2022

template <typename Functor>
struct for_each
{
    template <size_t Index = zero, typename... Args,
        if_lesser<Index, array_count<argument<zero, Args...>>> = true>
    static constexpr void unroll(Args&... args) noexcept
    {
        static_assert(!is_zero(array_count<argument<zero, Args...>>));

        Functor::fn(args[Index]...);

        if constexpr (Index != sub1(array_count<argument<zero, Args...>>))
        {
            unroll<add1(Index)>(args...);
        }
    }
};

struct xor2
{
    static constexpr void fn(auto& x, auto y) noexcept
    {
        x ^= y;
    }
};

// static_assert helper.
template <size_t Offset = zero>
constexpr auto zeroize2(auto a) noexcept
{
    auto copy{ a };
    for_each<xor2>::unroll<Offset>(copy, a);
    return copy;
}

static_assert(zeroize2(set3{ 1, 2, 3 }) == set3{ 0, 0, 0 });
static_assert(zeroize2<0>(set3{ 1, 2, 3 }) == set3{ 0, 0, 0 });
static_assert(zeroize2<1>(set3{ 1, 2, 3 }) == set3{ 1, 0, 0 });
static_assert(zeroize2<2>(set3{ 1, 2, 3 }) == set3{ 1, 2, 0 });
static_assert(zeroize2<3>(set3{ 1, 2, 3 }) == set3{ 1, 2, 3 });