[BlockVectorWindow] allow conversion to BlockVector

dune/istl/bvector.hh

@@ -4,6 +4,7 @@
 #ifndef DUNE_ISTL_BVECTOR_HH
 #define DUNE_ISTL_BVECTOR_HH
 
+#include <algorithm>
 #include <cmath>
 #include <complex>
 #include <initializer_list>
@@ -709,6 +710,14 @@ namespace Imp {
       return *this;
     }
 
+    //! copy into an independent BlockVector object
+    operator BlockVector<B, A>() const {
+      auto bv = BlockVector<B, A>(this->n);
+
+      std::copy(this->begin(), this->end(), bv.begin());
+
+      return bv;
+    }
 
     //===== window manipulation methods