Hashing concept on A and B key

headers/Containers/DualkeyMap.hpp

@@ -8,16 +8,17 @@
  */
 #ifndef GUARD_TOURMALINE_DUALKEYMAP_H
 #define GUARD_TOURMALINE_DUALKEYMAP_H
+#include "Hashing.hpp"
+
 #include <cstddef>
 #include <cstdint>
 #include <vector>
 
 namespace Tourmaline::Containers {
-template <typename AKey, typename BKey, typename Value,
+template <Hashable AKey, Hashable BKey, typename Value,
           uint64_t baseReservation = 1024,
           float reservationGrowthExponent = 1.5>
 class DualkeyMap {
-  constexpr static uint64_t EmptyKey = -1;
   DualkeyMap() {
     ValueList.reserve(baseReservation);
     HashList.reserve(baseReservation);

headers/Containers/Hashing.hpp

@@ -0,0 +1,21 @@
+/*
+ * SPDX-FileCopyrightText: Dora "cat" <cat@thenight.club>
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public License,
+ * v. 2.0. If a copy of the MPL was not distributed with this file, You can
+ * obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef GUARD_TOURMALINE_HASHING_H
+#define GUARD_TOURMALINE_HASHING_H
+#include <concepts>
+#include <functional>
+
+namespace Tourmaline::Containers {
+template <typename T>
+concept Hashable = requires(T x) {
+  { std::hash<T>{x}() } -> std::convertible_to<std::size_t>;
+};
+} // namespace Tourmaline::Containers
+#endif