[python] Add python cnversion for Dune::TupleVector

dune/fufem/python/conversion.hh

@@ -20,6 +20,10 @@
 #include <dune/common/fvector.hh>
 #include <dune/common/parametertree.hh>
 #include <dune/common/typetraits.hh>
+#include <dune/common/hybridutilities.hh>
+#include <dune/common/tuplevector.hh>
+#include <dune/common/indices.hh>
+#include <dune/common/rangeutilities.hh>
 
 #include <dune/geometry/utility/typefromvertexcount.hh>
 
@@ -373,6 +377,45 @@ struct Conversion<Dune::BlockVector<T> >
 };
 
 
+// conversion of FieldVector
+template<class... T>
+struct Conversion<Dune::TupleVector<T...> >
+{
+    enum {useDefaultConstructorConversion=true};
+    static void toC(PyObject* list, Dune::TupleVector<T...>& v)
+    {
+        static constexpr auto n = Dune::index_constant<sizeof...(T)>{};
+        if (not PySequence_Check(list))
+            DUNE_THROW(Dune::Exception, "cannot convert a non-sequence to a Dune::TupleVector<T...>");
+        else
+        {
+            if (PySequence_Size(list)!=v.size())
+                DUNE_THROW(Dune::Exception, "cannot convert a sequence of size" << PySequence_Size(list) << " to a Dune::TupleVector of size " << v.size());
+
+            Dune::Hybrid::forEach(Dune::range(n), [&](auto i) {
+                Reference(PySequence_GetItem(list, i)).toC(v[i]);
+            });
+            // The above is OK since PySequence_GetItem returns a new reference.
+            // With PyTuple_GetItem we would need one of the following since it
+            // returns a borrowed reference:
+            // Conversion<T>::toC(PySequence_GetItem(list, i), v[i]);
+            // Reference(Imp::inc(PySequence_GetItem(list, i))).toC(v[i]);
+        }
+    }
+
+    static PyObject* toPy(const Dune::TupleVector<T...>& v)
+    {
+        static constexpr auto n = Dune::index_constant<sizeof...(T)>{};
+        PyObject* tuple = PyTuple_New(n);
+        Dune::Hybrid::forEach(Dune::range(n), [&](auto i) {
+            PyTuple_SetItem(tuple, i, Imp::inc(makeObject(v[i])));
+        });
+        // We have to use inc() since PyTuple_SetItem STEALS a reference!
+        return tuple;
+    }
+};
+
+
 // conversion to dict to ParameterTree
 template<>
 struct Conversion<Dune::ParameterTree>