added operator() to change values

cpp/Tensor2.h

@@ -10,13 +10,13 @@
 
 namespace tensors {
 
-	/** Rank 2 Tensor */
-	template<int N1, int N2>
-	class Tensor2 {
-	protected:
+/** Rank 2 Tensor */
+template<int N1, int N2>
+class Tensor2 {
+protected:
 	Tensor1<N1> T[N2];
 
-	public:
+public:
 
 	/** default constructor */
 	Tensor2() {
@@ -35,7 +35,11 @@ namespace tensors {
 			T[j] = a(j);
 	}
 
-		double operator()(int i, int j) const {
+	const double & operator()(int i, int j) const {
+		return T[j](i);
+	}
+
+	double & operator()(int i, int j) {
 		return T[j](i);
 	}
 
@@ -44,7 +48,7 @@ namespace tensors {
 			N2, J> > operator()(Index<N1, I> i, Index<N2, J> j) const {
 		return Tensor2Expression<Tensor2, Index<N1, I> , Index<N2, J> > (*this);
 	}
-	};
+};
 
 } // namespace tensors