diff --git a/libs/util/include/psemek/util/array.hpp b/libs/util/include/psemek/util/array.hpp
index d58a0e76..bd221a2c 100644
--- a/libs/util/include/psemek/util/array.hpp
+++ b/libs/util/include/psemek/util/array.hpp
@@ -376,6 +376,21 @@ namespace psemek::util
 		data_ = std::move(data);
 	}
 
+	template <typename T, std::size_t N>
+	void mirror(array<T, N> & a, std::size_t i)
+	{
+		assert(i < N);
+
+		auto const s = a.dim(i);
+		for (auto idx : a.indices())
+		{
+			auto jdx = idx;
+			jdx[i] = s - 1 - jdx[i];
+			if (jdx[i] < idx[i])
+				std::swap(a(idx), a(jdx));
+		}
+	}
+
 	template <typename F, typename T, std::size_t N>
 	auto map(F && f, array<T, N> const & a)
 	{