lundi 27 février 2017

compare two unorderes type lists for equality

How can one check if two parameter packs are the same, ignoring their internal order?

So far I only have the frame (using std::tuple), but no functionality.

#include <tuple>
#include <type_traits>

template <typename, typename>
struct type_set_eq : std::false_type
{
};

template <typename ... Types1, typename ... Types2>
struct type_set_eq<std::tuple<Types1...>, std::tuple<Types2...>>
    : std::true_type
{
    // should only be true_type if the sets of types are equal
};

int main() {
    using t1 = std::tuple<int, double>;
    using t2 = std::tuple<double, int>;
    using t3 = std::tuple<int, double, char>;

    static_assert(type_set_eq<t1, t1>::value, "err");
    static_assert(type_set_eq<t1, t2>::value, "err");
    static_assert(!type_set_eq<t1, t3>::value, "err");
}

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