add various vector-space operations

[[Imported from SVN: r6299]]

dune/gfe/tensor3.hh

@@ -9,9 +9,82 @@ template <class T, int N1, int N2, int N3>
 class Tensor3
     : public Dune::array<Dune::FieldMatrix<T,N2,N3>,N1>
 {
+    public:
 
-
+        
+        static Tensor3<T,N1,N2,N3> product(const Dune::FieldVector<T,N1>& a, const Dune::FieldVector<T,N2>& b, const Dune::FieldVector<T,N3>& c)
+        {
+            Tensor3<T,N1,N2,N3> result;
+            
+            for (int i=0; i<N1; i++)
+                for (int j=0; j<N2; j++)
+                    for (int k=0; k<N3; k++)
+                        result[i][j][k] = a[i]*b[j]*c[k];
+                    
+            return result;
+        }
+    
+        static Tensor3<T,N1,N2,N3> product(const Dune::FieldMatrix<T,N1,N2>& ab, const Dune::FieldVector<T,N3>& c)
+        {
+            Tensor3<T,N1,N2,N3> result;
+            
+            for (int i=0; i<N1; i++)
+                for (int j=0; j<N2; j++)
+                    for (int k=0; k<N3; k++)
+                        result[i][j][k] = ab[i][j]*c[k];
+                    
+            return result;
+        }
+    
+        static Tensor3<T,N1,N2,N3> product(const Dune::FieldVector<T,N3>& a, const Dune::FieldMatrix<T,N1,N2>& bc)
+        {
+            Tensor3<T,N1,N2,N3> result;
+            
+            for (int i=0; i<N1; i++)
+                for (int j=0; j<N2; j++)
+                    for (int k=0; k<N3; k++)
+                        result[i][j][k] = a[i]*bc[j][k];
+                    
+            return result;
+        }
     
+    friend Tensor3<T,N1,N2,N3> operator+(const Tensor3<T,N1,N2,N3>& a, const Tensor3<T,N1,N2,N3>& b)
+    {
+            Tensor3<T,N1,N2,N3> result;
+            
+            for (int i=0; i<N1; i++)
+                for (int j=0; j<N2; j++)
+                    for (int k=0; k<N3; k++)
+                        result[i][j][k] = a[i][j][k] + b[i][j][k];
+                    
+            return result;
+    }
+
+    friend Tensor3<T,N1,N2,N3> operator-(const Tensor3<T,N1,N2,N3>& a, const Tensor3<T,N1,N2,N3>& b)
+    {
+            Tensor3<T,N1,N2,N3> result;
+            
+            for (int i=0; i<N1; i++)
+                for (int j=0; j<N2; j++)
+                    for (int k=0; k<N3; k++)
+                        result[i][j][k] = a[i][j][k] - b[i][j][k];
+                    
+            return result;
+    }
+
+    friend Tensor3<T,N1,N2,N3> operator*(const T& scalar, const Tensor3<T,N1,N2,N3>& tensor)
+    {
+        Tensor3<T,N1,N2,N3> result;
+            
+        for (int i=0; i<N1; i++)
+            for (int j=0; j<N2; j++)
+                for (int k=0; k<N3; k++)
+                    result[i][j][k] = scalar * tensor[i][j][k];
+                    
+        return result;
+        
+    }
+
 };
 
 #endif
\ No newline at end of file