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diff --git a/immer/detail/rbts/bits.hpp b/immer/detail/rbts/bits.hpp
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+//
+// 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 <cstdint>
+
+namespace immer {
+namespace detail {
+namespace rbts {
+
+using bits_t  = std::uint32_t;
+using shift_t = std::uint32_t;
+using count_t = std::uint32_t;
+using size_t  = std::size_t;
+
+template <bits_t B, typename T = count_t>
+constexpr T branches = T{1} << B;
+
+template <bits_t B, typename T = size_t>
+constexpr T mask = branches<B, T> - 1;
+
+template <bits_t B, bits_t BL>
+constexpr shift_t endshift = shift_t{BL} - shift_t{B};
+
+} // namespace rbts
+} // namespace detail
+} // namespace immer