diff --git a/libs/geom/include/psemek/geom/contains.hpp b/libs/geom/include/psemek/geom/contains.hpp
index 3fb65f00..579e1fe1 100644
--- a/libs/geom/include/psemek/geom/contains.hpp
+++ b/libs/geom/include/psemek/geom/contains.hpp
@@ -24,6 +24,21 @@ namespace psemek::geom
 		return true;
 	}
 
+	template <typename T>
+	bool half_open_contains(interval<T> const & i, T const & x)
+	{
+		return (i.min <= x) && (x < i.max);
+	}
+
+	template <typename T, std::size_t N>
+	bool half_open_contains(box<T, N> const & b, point<T, N> const & p)
+	{
+		for (std::size_t i = 0; i < N; ++i)
+			if (!half_open_contains(b[i], p[i]))
+				return false;
+		return true;
+	}
+
 	template <typename T>
 	bool contains(simplex<point<T, 2>, 2> const & t, point<T, 2> const & p)
 	{