1 files changed, 25 insertions, 0 deletions
diff --git a/boost/histogram/detail/replace_default.hpp b/boost/histogram/detail/replace_default.hpp
new file mode 100644
index 0000000000..16c4c071c4
--- /dev/null
+++ b/boost/histogram/detail/replace_default.hpp
@@ -0,0 +1,25 @@
+// Copyright 2015-2019 Hans Dembinski
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt
+// or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_HISTOGRAM_DETAIL_REPLACE_DEFAULT_HPP
+#define BOOST_HISTOGRAM_DETAIL_REPLACE_DEFAULT_HPP
+
+#include <boost/core/use_default.hpp>
+#include <type_traits>
+
+namespace boost {
+namespace histogram {
+namespace detail {
+
+template <class T, class Default>
+using replace_default =
+    std::conditional_t<std::is_same<T, boost::use_default>::value, Default, T>;
+
+} // namespace detail
+} // namespace histogram
+} // namespace boost
+
+#endif