region: add a free function region-region intersects

region.hpp

@@ -296,6 +296,16 @@ namespace cruft {
 
 
     ///////////////////////////////////////////////////////////////////////////
+    template <std::size_t S, typename T>
+    bool
+    intersects (
+        cruft::region<S,T> const &a,
+        cruft::region<S,T> const &b
+    ) {
+        return a.intersects (b);
+    }
+
+
     /// returns true if the supplied point lies within the supplied region
     /// inclusive of borders.
     template <size_t S, typename T>