diff --git a/AMDiS/src/expressions/functorN_expr.hpp b/AMDiS/src/expressions/functorN_expr.hpp
index e60ba4d2e1431e22df1fd4a80d83239f7f351605..f7a1e31bd66d67048ec69352cdfb341c224e059c 100644
--- a/AMDiS/src/expressions/functorN_expr.hpp
+++ b/AMDiS/src/expressions/functorN_expr.hpp
@@ -109,13 +109,13 @@ namespace AMDiS
     template <class R, class C, class... As>
     struct Function<R (C::*)(As...)>
     {
-	typedef R result_type;
+	    typedef R type;
     };
 
     template<class R, class C, class... As>
     struct Function<R (C::*)(As...) const>
     {
-	typedef R type;
+	    typedef R type;
     };
 
     template <class T>
@@ -128,11 +128,6 @@ namespace AMDiS
       typedef decltype(function_helper(&F::operator())) type;
     };
 
-    template <class R, class... As>
-    struct Functor<std::function<R(As...)> >
-    {
-      typedef R type;
-    };
 
     template <class F>
     struct Functor<F, typename void_<typename F::value_type>::type>
diff --git a/AMDiS/src/expressions/simplify_expr.hpp b/AMDiS/src/expressions/simplify_expr.hpp
index 2e659b8c364d0be1de80802904c04b62521ba148..5d154895c15accdc9b9ce92c7fe2812dd11cd70d 100644
--- a/AMDiS/src/expressions/simplify_expr.hpp
+++ b/AMDiS/src/expressions/simplify_expr.hpp
@@ -74,6 +74,16 @@ namespace AMDiS
       static type eval(RValue<T> const& t) { return t; }
     };
 
+    /// -(n) -> (-n)
+    template<class T>
+    struct Simplify< Negative<RValue<T> > >
+    {
+      typedef RValue<T> type;
+
+      static type eval(Negative<RValue<T> > const& t)
+      { return RValue<T>(-t.term.value); }
+    };
+
     /// -(N) -> (-N)
     template<int N>
     struct Simplify< Negative<CValue<N> > >
@@ -82,7 +92,6 @@ namespace AMDiS
 
       static type eval(Negative<CValue<N> > const& t)
       { return CValue<-N>(); }
-
     };
 
     /// -0 -> 0
@@ -439,14 +448,23 @@ namespace AMDiS
 
     /// (X + (-Y)) -> X - Y
     template<typename X, typename Y>
-    struct Simplify< Negative<Add<X, Negative<Y> > > >
+    struct Simplify< Add<X, Negative<Y> > >
     {
       typedef Subtract<X, Y> type;
 
-      static type eval(Negative<Add<X, Negative<Y> > > const& t)
+      static type eval(Add<X, Negative<Y> > const& t)
       { return t.term1 - t.term2.term; }
     };
 
+    template<typename Y>
+    struct Simplify< Add<CValue<0>, Negative<Y> > >
+    {
+      typedef Negative<Y> type;
+
+      static type eval(Add<CValue<0>, Negative<Y> > const& t)
+      { return t.term2; }
+    };
+
     /// -(X - Y) -> Y - X
     template<typename X, typename Y>
     struct Simplify< Negative<Subtract<X, Y> > >