added somewhat sinnfreie methods N(), M() - but for compilation they are so...

added somewhat sinnfreie methods N(), M() - but for compilation they are so far required by our implementation

[[Imported from SVN: r5706]]

dune/solvers/operators/nulloperator.hh

@@ -89,6 +89,17 @@ class NullOperator
         void operator*=(const field_type&)
         {}
 
+        size_type M() const
+        {
+            return 0;
+        }
+
+        size_type N() const
+        {
+            return 0;
+        }
+
+
 };
 
 #endif