try out: simplify automatic forces trait

elements/src/include/ae108/elements/AutomaticForcesTrait.h

@@ -27,12 +27,11 @@ namespace ae108::elements {
 /**
  * @brief Computes the forces by differentiation of the energy.
  */
-template <class Element_> struct AutomaticForcesTrait {
-  template <class Element>
-  typename Element::Forces
-  operator()(const Element &element,
+template <class Element> struct AutomaticForcesTrait {
+  static typename Element::Forces
+  compute(const Element &element,
              const typename Element::NodalDisplacements &u,
-             const typename Element::Time &time) const {
+             const typename Element::Time &time) {
     auto result = typename Element::Forces();
     auto result_matrix = tensor::as_matrix_of_rows(result);
 

elements/src/include/ae108/elements/ElementConcept.h

@@ -95,7 +95,7 @@ concept ElementConcept = requires(const T a) {
 template <ElementConcept ElementImpl> struct Element : ElementImpl {
   using Energy = typename ElementImpl::Energy;
   using Time = typename ElementImpl::Energy;
-  using NodalDisplacements = typename ElementImpl::NodalDisplacement;
+  using NodalDisplacements = typename ElementImpl::NodalDisplacements;
   static constexpr auto size() { return ElementImpl::size_; }
 
   Energy ComputeEnergy(const NodalDisplacements &displacements,

elements/src/include/ae108/elements/Minimal.h

@@ -55,8 +55,15 @@ struct ComputeEnergyTrait<Minimal<Size_, Dimension_, DegreesOfFreedom_>> {
  */
 template <std::size_t Size_, std::size_t Dimension_,
           std::size_t DegreesOfFreedom_>
-struct ComputeForcesTrait<Minimal<Size_, Dimension_, DegreesOfFreedom_>>
-    : AutomaticForcesTrait<Minimal<Size_, Dimension_, DegreesOfFreedom_>> {};
+struct ComputeForcesTrait<Minimal<Size_, Dimension_, DegreesOfFreedom_>>{
+  template <class Element>
+  typename Element::Forces
+  operator()(const Element &element,
+             const typename Element::NodalDisplacements &u,
+             const typename Element::Time &time) const noexcept {
+    return AutomaticForcesTrait<Minimal<Size_, Dimension_, DegreesOfFreedom_>>::compute(element, u, time);
+  }
+};
 
 /**
  * @brief Computes the stiffness matrix by differentiating the forces.

elements/src/include/ae108/elements/automatic_forces.h

@@ -29,7 +29,7 @@ typename Element::Forces
 automatic_forces(const Element &element,
                  const typename Element::NodalDisplacements &displacements,
                  const typename Element::Time &time) {
-  return AutomaticForcesTrait<Element>()(element, displacements, time);
+  return AutomaticForcesTrait<Element>::compute(element, displacements, time);
 }
 
 } // namespace ae108::elements
\ No newline at end of file

elements/src/include/ae108/elements/compute_forces.h

@@ -27,11 +27,7 @@ typename Element::Forces
 compute_forces(const Element &element,
                const typename Element::NodalDisplacements &displacements,
                const typename Element::Time &time) {
-  if constexpr (ElementConcept<Element>) {
-    return element.computeForces(displacements, time);
-  } else {
-    return ComputeForcesTrait<Element>()(element, displacements, time);
-  }
+  return ComputeForcesTrait<Element>()(element, displacements, time);
 }
 
 } // namespace ae108::elements
\ No newline at end of file

elements/test/ForceElement_Test.cc

@@ -43,8 +43,7 @@ template <class Element> typename Element::Force create_test_force() noexcept {
 template <class Element_> struct Configuration {
   using Element = Element_;
   static Element create_element() noexcept {
-    return {// .force =
-            create_test_force<Element_>()};
+    return { .force = create_test_force<Element_>()};
   }
 
   static typename Element::Time create_time() noexcept {
@@ -60,7 +59,7 @@ struct ForceElement_Test : Test {
   static constexpr auto dimension = 2;
 
   using Element = ForceElement<dimension>;
-  const Element element = {// .force =
+  const Element element = {.force =
                            create_test_force<Element>()};
 };