diff --git a/utils.h b/utils.h
new file mode 100644
--- /dev/null
+++ b/utils.h
@@ -0,0 +1,8 @@
+
+// credits: peppe@stackoverflow [http://stackoverflow.com/a/16795664/432492]
+template<typename... Args> struct SELECT {
+    template<typename C, typename R>
+    static constexpr auto OVERLOAD_OF( R (C::*pmf)(Args...) ) -> decltype(pmf) {
+        return pmf;
+    }
+};