thelfer · Oct 2, 2026 · Oct 2, 2026 · Oct 2, 2026
diff --git a/include/CMakeLists.txt b/include/CMakeLists.txt
@@ -99,6 +99,7 @@ if(enable-mgis-function)
   mgis_header(MGIS/Function Algorithms.hxx)
   mgis_header(MGIS/Function Algorithms.ixx)
   mgis_header(MGIS/Function Buffer.hxx)
+  mgis_header(MGIS/Function DataViewConcept.hxx)
   mgis_header(MGIS/Function CoalescedMemoryAccessFunctionViewBase.hxx)
   mgis_header(MGIS/Function CoalescedMemoryAccessFunctionViewBase.ixx)
   mgis_header(MGIS/Function StridedCoalescedMemoryAccessFunctionViewBase.hxx)
@@ -108,6 +109,8 @@ if(enable-mgis-function)
     mgis_header(MGIS/Function/CUDA Algorithms.ixx)
   endif(enable-cuda-algorithms)
   if(MGIS_HAVE_TFEL)
+    mgis_header(MGIS/Function/TFEL General.hxx)
+    mgis_header(MGIS/Function/TFEL DataView.hxx)
     mgis_header(MGIS/Function/TFEL Quantity.hxx)
     mgis_header(MGIS/Function/TFEL QuantityView.hxx)
     mgis_header(MGIS/Function/TFEL QuantityView.ixx)

diff --git a/include/MGIS/Function/DataViewConcept.hxx b/include/MGIS/Function/DataViewConcept.hxx
@@ -0,0 +1,38 @@
+/*!
+ * \file   MGIS/Function/DataViewConcept.hxx
+ * \brief  This file declares `DataViewConcept`
+ * \author Thomas Helfer
+ * \date   02/10/2026
+ */
+
+#ifndef LIB_MGIS_FUNCTION_DATAVIEWCONCEPT_HXX
+#define LIB_MGIS_FUNCTION_DATAVIEWCONCEPT_HXX
+
+#include <span>
+#include <type_traits>
+
+namespace mgis::function::internals {
+
+  /*!
+   * \brief this class must be specialised
+   * for class holding views to data, such as
+   * std::span or tfel::math::View
+   */
+  template <typename T>
+  struct IsDataView : std::false_type {};
+
+  //! \brief partial specialisation for std::span
+  template <class T, std::size_t Extent>
+  struct IsDataView<::std::span<T, Extent>> : std::true_type{};
+
+}  // end of namespace mgis::function::internals
+
+namespace mgis::function {
+
+  //! \brief a concept used to distinguish views from data
+  template <typename T>
+  concept DataViewConcept = ::mgis::function::internals::IsDataView<T>::value;
+
+}  // end of namespace mgis::function
+
+#endif /* LIB_MGIS_FUNCTION_DATAVIEWCONCEPT_HXX */
diff --git a/include/MGIS/Function/TFEL/CoalescedMemoryAccessCompositeTensorsView.hxx b/include/MGIS/Function/TFEL/CoalescedMemoryAccessCompositeTensorsView.hxx
@@ -24,6 +24,7 @@
 #include <type_traits>
 #include "TFEL/Math/Array/CoalescedView.hxx"
 #include "MGIS/Function/CoalescedMemoryAccessFunctionViewBase.hxx"
+#include "MGIS/Function/TFEL/General.hxx"
 #include "MGIS/Function/TFEL/TensorConcept.hxx"
 
 namespace mgis::function {

diff --git a/include/MGIS/Function/TFEL/CoalescedMemoryAccessTensorView.hxx b/include/MGIS/Function/TFEL/CoalescedMemoryAccessTensorView.hxx
@@ -20,6 +20,7 @@
 #define LIB_MGIS_FUNCTION_TFEL_COALESCEDMEMORYACCESSTENSORVIEW_HXX
 
 #include "TFEL/Math/Array/CoalescedView.hxx"
+#include "MGIS/Function/TFEL/General.hxx"
 #include "MGIS/Function/CoalescedMemoryAccessFunctionViewBase.hxx"
 #include "MGIS/Function/TFEL/TensorConcept.hxx"
 

diff --git a/include/MGIS/Function/TFEL/DataView.hxx b/include/MGIS/Function/TFEL/DataView.hxx
@@ -0,0 +1,31 @@
+/*!
+ * \file   MGIS/Function/TFEL/DataView.hxx
+ * \brief  This file specializes the `IsDataView` class for TFEL' types
+ * \author Thomas Helfer
+ * \date   02/10/2026
+ */
+
+#ifndef LIB_MGIS_FUNCTION_TFEL_DATAVIEW_HXX
+#define LIB_MGIS_FUNCTION_TFEL_DATAVIEW_HXX
+
+#include "TFEL/Math/Array/View.hxx"
+#include "TFEL/Math/Array/CoalescedView.hxx"
+#include "MGIS/Function/DataViewConcept.hxx"
+
+namespace mgis::function::internals {
+
+  //! \brief partial specialisation for tfel::math::View
+  template <typename MappedType, typename IndexingPolicyType>
+  struct IsDataView<::tfel::math::View<MappedType, IndexingPolicyType>>
+    : std::true_type{};
+
+  //! \brief partial specialisation for tfel::math::CoalescedView
+  template <
+      ::tfel::math::MappableMathObjectUsingCoalescedViewConcept MappedType,
+      typename IndexingPolicyType>
+  struct IsDataView<::tfel::math::CoalescedView<MappedType, IndexingPolicyType>>
+    : std::true_type{};
+
+}  // end of namespace mgis::function::internals
+
+#endif /* LIB_MGIS_FUNCTION_TFEL_DATAVIEW_HXX */
diff --git a/include/MGIS/Function/TFEL/General.hxx b/include/MGIS/Function/TFEL/General.hxx
@@ -0,0 +1,13 @@
+/*!
+ * \file   MGIS/Function/TFEL/General.hxx
+ * \brief  This file contains common defintions to integrate TFEL's types properly
+ * \author Thomas Helfer
+ * \date   02/10/2026
+ */
+
+#ifndef LIB_MGIS_FUNCTION_TFEL_GENERAL_HXX
+#define LIB_MGIS_FUNCTION_TFEL_GENERAL_HXX
+
+#include "MGIS/Function/TFEL/DataView.hxx"
+
+#endif /* LIB_MGIS_FUNCTION_TFEL_GENERAL_HXX */
diff --git a/include/MGIS/Function/TFEL/Mechanics.hxx b/include/MGIS/Function/TFEL/Mechanics.hxx
@@ -22,6 +22,7 @@
 #include <type_traits>
 #include "TFEL/Material/FiniteStrainBehaviourTangentOperator.hxx"
 #include "MGIS/Function/Evaluator.hxx"
+#include "MGIS/Function/TFEL/General.hxx"
 #include "MGIS/Function/TFEL/Tensors.hxx"
 
 namespace mgis::function::internals {

diff --git a/include/MGIS/Function/TFEL/Quantity.hxx b/include/MGIS/Function/TFEL/Quantity.hxx
@@ -21,6 +21,7 @@
 
 #include "TFEL/Math/qt.hxx"
 #include "MGIS/Function/CompileTimeSize.hxx"
+#include "MGIS/Function/TFEL/General.hxx"
 #include "MGIS/Function/TFEL/QuantityView.hxx"
 #include "MGIS/Function/TFEL/QuantityModifier.hxx"
 

diff --git a/include/MGIS/Function/TFEL/QuantityModifier.hxx b/include/MGIS/Function/TFEL/QuantityModifier.hxx
@@ -22,6 +22,7 @@
 #include "MGIS/Contract.hxx"
 #include "MGIS/Function/SpaceConcept.hxx"
 #include "MGIS/Function/EvaluatorConcept.hxx"
+#include "MGIS/Function/TFEL/General.hxx"
 
 namespace mgis::function {
 

diff --git a/include/MGIS/Function/TFEL/QuantityView.hxx b/include/MGIS/Function/TFEL/QuantityView.hxx
@@ -21,6 +21,7 @@
 
 #include "TFEL/Math/qt.hxx"
 #include "MGIS/Function/FunctionConcept.hxx"
+#include "MGIS/Function/TFEL/General.hxx"
 
 namespace mgis::function {
 

diff --git a/include/MGIS/Function/TFEL/StridedCoalescedMemoryAccessCompositeTensorsView.hxx b/include/MGIS/Function/TFEL/StridedCoalescedMemoryAccessCompositeTensorsView.hxx
@@ -25,6 +25,7 @@
 #include <type_traits>
 #include "TFEL/Math/Array/StridedCoalescedView.hxx"
 #include "MGIS/Function/StridedCoalescedMemoryAccessFunctionViewBase.hxx"
+#include "MGIS/Function/TFEL/General.hxx"
 #include "MGIS/Function/TFEL/TensorConcept.hxx"
 
 namespace mgis::function {

diff --git a/include/MGIS/Function/TFEL/StridedCoalescedMemoryAccessTensorView.hxx b/include/MGIS/Function/TFEL/StridedCoalescedMemoryAccessTensorView.hxx
@@ -21,6 +21,7 @@
 
 #include "TFEL/Math/Array/StridedCoalescedView.hxx"
 #include "MGIS/Function/StridedCoalescedMemoryAccessFunctionViewBase.hxx"
+#include "MGIS/Function/TFEL/General.hxx"
 #include "MGIS/Function/TFEL/TensorConcept.hxx"
 
 namespace mgis::function {

diff --git a/include/MGIS/Function/TFEL/TensorConcept.hxx b/include/MGIS/Function/TFEL/TensorConcept.hxx
@@ -32,6 +32,7 @@
 #include "TFEL/Math/st2tost2.hxx"
 #include "TFEL/Math/Array/View.hxx"
 #include "MGIS/Function/CompileTimeSize.hxx"
+#include "MGIS/Function/TFEL/General.hxx"
 
 namespace mgis::function {
 

diff --git a/include/MGIS/Function/TFEL/TensorModifier.hxx b/include/MGIS/Function/TFEL/TensorModifier.hxx
@@ -21,6 +21,7 @@
 
 #include "MGIS/Function/Evaluator.hxx"
 #include "MGIS/Function/EvaluatorModifierBase.hxx"
+#include "MGIS/Function/TFEL/General.hxx"
 #include "MGIS/Function/TFEL/TensorConcept.hxx"
 
 namespace mgis::function {

diff --git a/include/MGIS/Function/TFEL/TensorModifier.ixx b/include/MGIS/Function/TFEL/TensorModifier.ixx
@@ -31,7 +31,11 @@ namespace mgis::function {
                                                   EvaluatorType>)  //
       constexpr auto TensorModifier<TensorType, EvaluatorType>::apply(
           const evaluator_result<EvaluatorType>& values) const {
-    return tfel::math::map<const TensorType>(values.data());
+    if constexpr (DataViewConcept<evaluator_result<EvaluatorType>>) {
+      return tfel::math::map<const TensorType>(values.data());
+    } else {
+      return TensorType(tfel::math::map<const TensorType>(values.data()));
+    }
   }  // end of apply
 
   template <TensorConcept TensorType, EvaluatorConcept EvaluatorType>

diff --git a/include/MGIS/Function/TFEL/TensorOperations.hxx b/include/MGIS/Function/TFEL/TensorOperations.hxx
@@ -24,6 +24,7 @@
 #include "MGIS/Config.hxx"
 #include "MGIS/Function/BasicLinearSpace.hxx"
 #include "MGIS/Function/Function.hxx"
+#include "MGIS/Function/TFEL/General.hxx"
 
 namespace mgis::function {
 

diff --git a/include/MGIS/Function/TFEL/TensorView.hxx b/include/MGIS/Function/TFEL/TensorView.hxx
@@ -24,6 +24,7 @@
 #include <span>
 #include "MGIS/Contract.hxx"
 #include "MGIS/Function/Function.hxx"
+#include "MGIS/Function/TFEL/General.hxx"
 #include "MGIS/Function/TFEL/TensorConcept.hxx"
 
 namespace mgis::function {

diff --git a/include/MGIS/Function/TFEL/TensorialFunction.hxx b/include/MGIS/Function/TFEL/TensorialFunction.hxx
@@ -20,6 +20,7 @@
 #define LIB_MGIS_FUNCTION_TFEL_TENSORIALFUNCTION_HXX
 
 #include "MGIS/Function/Function.hxx"
+#include "MGIS/Function/TFEL/General.hxx"
 #include "MGIS/Function/TFEL/Tensors.hxx"
 
 namespace mgis::function {

diff --git a/include/MGIS/Function/TFEL/Tensors.hxx b/include/MGIS/Function/TFEL/Tensors.hxx
@@ -22,6 +22,7 @@
 #include "TFEL/Math/Forward/General.hxx"
 #include "MGIS/Function/FunctionConcept.hxx"
 #include "MGIS/Function/EvaluatorConcept.hxx"
+#include "MGIS/Function/TFEL/General.hxx"
 #include "MGIS/Function/TFEL/TensorConcept.hxx"
 #include "MGIS/Function/TFEL/TensorView.hxx"
 #include "MGIS/Function/TFEL/TensorModifier.hxx"