Add convenience functions to create result instances.

dune/matrix-vector/axpy.hh

@@ -23,7 +23,6 @@ namespace MatrixVector {
             bool BisScalar, bool CisScalar>
   struct ScaledProductHelper;
 
-
   /** \brief Add a product to some matrix or vector
    *
    * This function computes a+=b*c.
@@ -94,6 +93,21 @@ namespace MatrixVector {
                         isScalar<D>()>::addProduct(a, -b, c, d);
   }
 
+  template <class A, class... BCD>
+  A getAddProduct(const A& a, BCD&&... bcd) {
+    auto sum = a;
+    addProduct(sum, std::forward<BCD>(bcd)...);
+    return sum;
+  }
+
+  template <class A, class... BCD>
+  A getSubtractProduct(const A& a, BCD&&... bcd) {
+    auto difference = a;
+    subtractProduct(difference, std::forward<BCD>(bcd)...);
+    return difference;
+  }
+
+
   /** \brief Internal helper class for product operations
    *
    */