Add helper to obtain matrix with fieldmatrix type leaves.

dune/matrix-vector/CMakeLists.txt

@@ -6,6 +6,7 @@ add_subdirectory(types)
 install(FILES
   addtodiagonal.hh
   algorithm.hh
+  asfieldmatrix.hh
   axpy.hh
   axy.hh
   blockmatrixview.hh

dune/matrix-vector/asfieldmatrix.hh

+#ifndef DUNE_MATRIX_VECTOR_ASFIELDMATRIX_HH
+#define DUNE_MATRIX_VECTOR_ASFIELDMATRIX_HH
+
+#include <dune/common/fmatrix.hh>
+#include <dune/common/diagonalmatrix.hh>
+#include <dune/istl/scaledidmatrix.hh>
+#include <dune/istl/bcrsmatrix.hh>
+#include <dune/istl/multitypeblockmatrix.hh>
+#include <dune/matrix-vector/types/multitypematrix.hh>
+
+namespace Dune {
+namespace MatrixVector {
+
+template <class>
+struct AsFieldMatrix;
+
+template <class M>
+using AsFieldMatrix_t = typename AsFieldMatrix<M>::type;
+
+template <class K, int n, int m>
+struct AsFieldMatrix<FieldMatrix<K, n, m>> {
+  using type = FieldMatrix<K, n, m>;
+};
+
+template <class K, int n>
+struct AsFieldMatrix<DiagonalMatrix<K, n>> {
+  using type = FieldMatrix<K, n, n>;
+};
+
+template <class K, int n>
+struct AsFieldMatrix<ScaledIdentityMatrix<K, n>> {
+  using type = FieldMatrix<K, n, n>;
+};
+
+template <class BlockMatrix>
+struct AsFieldMatrix<BCRSMatrix<BlockMatrix>> {
+  using type = BCRSMatrix<AsFieldMatrix_t<BlockMatrix>>;
+};
+
+template <class... Args>
+struct AsFieldMatrix<MultiTypeBlockMatrix<Args...>> {
+  using type = MultiTypeBlockMatrix<AsFieldMatrix_t<Args>...>;
+};
+
+template <class... Args>
+struct AsFieldMatrix<MultiTypeMatrix<Args...>> {
+  using type = MultiTypeMatrix<AsFieldMatrix_t<Args>...>;
+};
+
+} // end namespace MatrixVector
+} // end namespace Dune
+
+#endif // DUNE_MATRIX_VECTOR_ASFIELDMATRIX_HH