FEValuesViews::View<dim,spacedim,Extractor>

diff --git a/doc/news/changes/minor/20190320LucaHeltai b/doc/news/changes/minor/20190320LucaHeltai
new file mode 100644 (file)
index 0000000..5d1cbf8
--- /dev/null
+++ b/doc/news/changes/minor/20190320LucaHeltai
@@ -0,0 +1,5 @@
+New: The type alias FEValuesViews::View now allows one to infer the correct FEValuesViews type 
+that would be returned by FEValuesBase::operator[]() when called with a specified extractor type from the 
+FEValuesExtractors namespace. 
+<br>
+(Luca Heltai, 2019/03/20)

diff --git a/include/deal.II/fe/fe_values.h b/include/deal.II/fe/fe_values.h
index 713f1c64adad43fc7ffa67b2a500dc21f0f0d5fa..71b50d966407160d03eab89ecaa46e7ec58c0ff0 100644 (file)
--- a/include/deal.II/fe/fe_values.h
+++ b/include/deal.II/fe/fe_values.h
@@ -1871,6 +1871,69 @@ namespace internal
 {
   namespace FEValuesViews
   {
+    /**
+     * A class whose specialization is used to define what FEValuesViews
+     * object corresponds to the given FEValuesExtractors object.
+     *
+     * @author Luca Heltai, 2019.
+     */
+    template <int dim, int spacedim, typename Extractor>
+    struct ViewType
+    {};
+
+    /**
+     * A class whose specialization is used to define what FEValuesViews
+     * object corresponds to the given FEValuesExtractors object.
+     *
+     * When using FEValuesExtractors::Scalar, the corresponding view is an
+     * FEValuesViews::Scalar<dim, spacedim>.
+     */
+    template <int dim, int spacedim>
+    struct ViewType<dim, spacedim, FEValuesExtractors::Scalar>
+    {
+      using type = typename dealii::FEValuesViews::Scalar<dim, spacedim>;
+    };
+
+    /**
+     * A class whose specialization is used to define what FEValuesViews
+     * object corresponds to the given FEValuesExtractors object.
+     *
+     * When using FEValuesExtractors::Vector, the corresponding view is an
+     * FEValuesViews::Vector<dim, spacedim>.
+     */
+    template <int dim, int spacedim>
+    struct ViewType<dim, spacedim, FEValuesExtractors::Vector>
+    {
+      using type = typename dealii::FEValuesViews::Vector<dim, spacedim>;
+    };
+
+    /**
+     * A class whose specialization is used to define what FEValuesViews
+     * object corresponds to the given FEValuesExtractors object.
+     *
+     * When using FEValuesExtractors::Tensor<rank>, the corresponding view is an
+     * FEValuesViews::Tensor<rank, dim, spacedim>.
+     */
+    template <int dim, int spacedim, int rank>
+    struct ViewType<dim, spacedim, FEValuesExtractors::Tensor<rank>>
+    {
+      using type = typename dealii::FEValuesViews::Tensor<rank, dim, spacedim>;
+    };
+
+    /**
+     * A class whose specialization is used to define what FEValuesViews
+     * object corresponds to the given FEValuesExtractors object.
+     *
+     * When using FEValuesExtractors::SymmetricTensor<rank>, the corresponding
+     * view is an FEValuesViews::SymmetricTensor<rank, dim, spacedim>.
+     */
+    template <int dim, int spacedim, int rank>
+    struct ViewType<dim, spacedim, FEValuesExtractors::SymmetricTensor<rank>>
+    {
+      using type =
+        typename dealii::FEValuesViews::SymmetricTensor<rank, dim, spacedim>;
+    };
+
     /**
      * A class objects of which store a collection of FEValuesViews::Scalar,
      * FEValuesViews::Vector, etc object. The FEValuesBase class uses it to
@@ -1900,6 +1963,18 @@ namespace internal
   } // namespace FEValuesViews
 } // namespace internal
 
+namespace FEValuesViews
+{
+  /**
+   * A templated alias that associates to a given Extractor class
+   * the corresponding view in FEValuesViews.
+   *
+   * @author Luca Heltai, 2019.
+   */
+  template <int dim, int spacedim, typename Extractor>
+  using View =
+    typename internal::FEValuesViews::ViewType<dim, spacedim, Extractor>::type;
+} // namespace FEValuesViews
 
 
 /**

diff --git a/tests/fe/fe_values_views_types.cc b/tests/fe/fe_values_views_types.cc
new file mode 100644 (file)
index 0000000..e6f5739
--- /dev/null
+++ b/tests/fe/fe_values_views_types.cc
@@ -0,0 +1,67 @@
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2019 by the deal.II authors
+//
+// This file is part of the deal.II library.
+//
+// The deal.II library is free software; you can use it, redistribute
+// it, and/or modify it under the terms of the GNU Lesser General
+// Public License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+// The full text of the license can be found in the file LICENSE.md at
+// the top level directory of deal.II.
+//
+// ---------------------------------------------------------------------
+
+// Test FEValuesViews::View<dim,spacedim,Extractor>
+
+#include <deal.II/base/utilities.h>
+
+#include <deal.II/fe/fe_values.h>
+
+#include "../tests.h"
+
+template <int dim, int spacedim, typename Extractor>
+void
+test(const Extractor &)
+{
+  typename FEValuesViews::View<dim, spacedim, Extractor>::template OutputType<
+    double>::value_type t1;
+
+  typename FEValuesViews::View<dim, spacedim, Extractor>::template OutputType<
+    double>::gradient_type t2;
+
+  deallog << "Test<" << Utilities::dim_string(dim, spacedim) << ">" << std::endl
+          << Utilities::type_to_string(t1) << std::endl
+          << Utilities::type_to_string(t2) << std::endl;
+}
+
+int
+main()
+{
+  initlog();
+
+  FEValuesExtractors::Scalar    scalar(0);
+  FEValuesExtractors::Vector    vector(1);
+  FEValuesExtractors::Tensor<2> tensor(2);
+
+  test<1, 1>(scalar);
+  test<1, 1>(vector);
+  test<1, 1>(tensor);
+
+  test<1, 2>(scalar);
+  test<1, 2>(vector);
+  test<1, 2>(tensor);
+
+  test<2, 2>(scalar);
+  test<2, 2>(vector);
+  test<2, 2>(tensor);
+
+  test<2, 3>(scalar);
+  test<2, 3>(vector);
+  test<2, 3>(tensor);
+
+  test<3, 3>(scalar);
+  test<3, 3>(vector);
+  test<3, 3>(tensor);
+}

diff --git a/tests/fe/fe_values_views_types.output b/tests/fe/fe_values_views_types.output
new file mode 100644 (file)
index 0000000..5eacce9
--- /dev/null
+++ b/tests/fe/fe_values_views_types.output
@@ -0,0 +1,46 @@
+
+DEAL::Test<1>
+DEAL::double
+DEAL::dealii::Tensor<1, 1, double>
+DEAL::Test<1>
+DEAL::dealii::Tensor<1, 1, double>
+DEAL::dealii::Tensor<2, 1, double>
+DEAL::Test<1>
+DEAL::dealii::Tensor<2, 1, double>
+DEAL::dealii::Tensor<3, 1, double>
+DEAL::Test<1,2>
+DEAL::double
+DEAL::dealii::Tensor<1, 2, double>
+DEAL::Test<1,2>
+DEAL::dealii::Tensor<1, 2, double>
+DEAL::dealii::Tensor<2, 2, double>
+DEAL::Test<1,2>
+DEAL::dealii::Tensor<2, 2, double>
+DEAL::dealii::Tensor<3, 2, double>
+DEAL::Test<2>
+DEAL::double
+DEAL::dealii::Tensor<1, 2, double>
+DEAL::Test<2>
+DEAL::dealii::Tensor<1, 2, double>
+DEAL::dealii::Tensor<2, 2, double>
+DEAL::Test<2>
+DEAL::dealii::Tensor<2, 2, double>
+DEAL::dealii::Tensor<3, 2, double>
+DEAL::Test<2,3>
+DEAL::double
+DEAL::dealii::Tensor<1, 3, double>
+DEAL::Test<2,3>
+DEAL::dealii::Tensor<1, 3, double>
+DEAL::dealii::Tensor<2, 3, double>
+DEAL::Test<2,3>
+DEAL::dealii::Tensor<2, 3, double>
+DEAL::dealii::Tensor<3, 3, double>
+DEAL::Test<3>
+DEAL::double
+DEAL::dealii::Tensor<1, 3, double>
+DEAL::Test<3>
+DEAL::dealii::Tensor<1, 3, double>
+DEAL::dealii::Tensor<2, 3, double>
+DEAL::Test<3>
+DEAL::dealii::Tensor<2, 3, double>
+DEAL::dealii::Tensor<3, 3, double>