merge(3p/immer): Subtree merge at 'ad3e3556d' as 'third_party/immer'

Change-Id: I9636a41ad44b4218293833fd3e9456d9b07c731b

third_party/immer/immer/map_transient.hpp

@@ -0,0 +1,41 @@
+//
+// immer: immutable data structures for C++
+// Copyright (C) 2016, 2017, 2018 Juan Pedro Bolivar Puente
+//
+// This software is distributed under the Boost Software License, Version 1.0.
+// See accompanying file LICENSE or copy at http://boost.org/LICENSE_1_0.txt
+//
+
+#pragma once
+
+#include <immer/detail/hamts/champ.hpp>
+#include <immer/memory_policy.hpp>
+
+#include <functional>
+
+namespace immer {
+
+/*!
+ * @rst
+ *
+ * .. admonition:: Become a sponsor!
+ *    :class: danger
+ *
+ *    This component is planned but it has **not been implemented yet**.
+ *
+ *    Transiens can critically improve the performance of applications
+ *    intensively using ``set`` and ``map``. If you are working for an
+ *    organization using the library in a commercial project, please consider
+ *    **sponsoring this work**: juanpe@sinusoid.al
+ *
+ * @endrst
+ */
+template <typename K,
+          typename T,
+          typename Hash           = std::hash<K>,
+          typename Equal          = std::equal_to<K>,
+          typename MemoryPolicy   = default_memory_policy,
+          detail::hamts::bits_t B = default_bits>
+class map_transient;
+
+} // namespace immer