1 files changed, 15 insertions, 0 deletions
diff --git a/src/utils/cpp/hash_combine.hpp b/src/utils/cpp/hash_combine.hpp
new file mode 100644
index 00000000..65c0c8ad
--- /dev/null
+++ b/src/utils/cpp/hash_combine.hpp
@@ -0,0 +1,15 @@
+#ifndef INCLUDED_SRC_UTILS_CPP_HASH_COMBINE_HPP
+#define INCLUDED_SRC_UTILS_CPP_HASH_COMBINE_HPP
+
+#include "gsl-lite/gsl-lite.hpp"
+
+// Taken from Boost, as hash_combine did not yet make it to STL.
+// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0814r0.pdf
+template <class T>
+inline auto hash_combine(gsl::not_null<std::size_t*> const& seed, T const& v)
+    -> void {
+    *seed ^=
+        std::hash<T>{}(v) + 0x9e3779b9 + (*seed << 6) + (*seed >> 2);  // NOLINT
+}
+
+#endif