diff --git a/test/triqs/arrays/diagonal_matrix.cpp b/test/triqs/arrays/diagonal_matrix.cpp
new file mode 100644
index 00000000..43e4f3d5
--- /dev/null
+++ b/test/triqs/arrays/diagonal_matrix.cpp
@@ -0,0 +1,71 @@
+/*******************************************************************************
+ *
+ * TRIQS: a Toolbox for Research in Interacting Quantum Systems
+ *
+ * Copyright (C) 2013 by O. Parcollet
+ *
+ * TRIQS is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * TRIQS is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * TRIQS. If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+#include <triqs/arrays.hpp>
+#include <iostream>
+
+namespace triqs { namespace arrays { 
+
+ template<typename T> class immutable_diagonal_matrix_view : TRIQS_MODEL_CONCEPT(ImmutableMatrix) { 
+  array_view<T,1> data;
+  public:
+
+  //immutable_diagonal_matrix_view(size_t i=1) : data ( array<T,1>(i)) {}
+  immutable_diagonal_matrix_view(array_view<T,1> v) : data (v) {}
+ 
+  // the ImmutableMatrix concept 
+  typedef T value_type;
+  T operator()(size_t i, size_t j) const { return (i==j ? data(i) : 0);}
+
+  typedef indexmaps::cuboid::domain_t<2> domain_type;
+  domain_type domain() const { auto s = data.shape()[0]; return mini_vector<size_t,2>(s,s);}
+
+  //
+  friend std::ostream & operator<<(std::ostream & out, immutable_diagonal_matrix_view const & d) { return out<<"diagonal_matrix "<<d.data;}
+  
+  // ----------------------
+  // should be remove from concept. redundant....
+  // need to clean dim0, dim1 and shape and make them free function everywhere (deduced from domain)
+  size_t dim0() const { return data.shape()[0];}
+  size_t dim1() const { return data.shape()[0];}
+  mini_vector<size_t,2> shape() const { auto s = data.shape()[0]; return mini_vector<size_t,2>(s,s);}
+ 
+ };
+ 
+}}
+
+using namespace triqs::arrays;
+
+int main(int argc, char **argv) {
+
+ auto a = array<int,1> { 1,2,3,4};
+
+ auto d = immutable_diagonal_matrix_view<int>(a);
+
+ std::cout  << d<< std::endl;
+ std::cout << matrix<int>( 2* d) << std::endl;
+ std::cout << matrix<int>( d * d) << std::endl;
+ return 0;
+}
+
+
+
+
+
diff --git a/test/triqs/arrays/reinterpret_view.cpp b/test/triqs/arrays/reinterpret_view.cpp
new file mode 100644
index 00000000..7bfc6abd
--- /dev/null
+++ b/test/triqs/arrays/reinterpret_view.cpp
@@ -0,0 +1,45 @@
+/*******************************************************************************
+ *
+ * TRIQS: a Toolbox for Research in Interacting Quantum Systems
+ *
+ * Copyright (C) 2011 by O. Parcollet
+ *
+ * TRIQS is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * TRIQS is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * TRIQS. If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+
+#include <triqs/arrays.hpp>
+#include <iostream>
+
+namespace triqs { namespace arrays { 
+
+ template <typename V, int R, ull_t Opt, ull_t To, typename ... I>  
+  array_view<V, sizeof...(I), Opt> reinterpret_array_view (array<V,R,Opt,To> const & a, I ... index) { 
+   static int constexpr rank = sizeof...(I);
+   typedef array_view<V, rank, Opt, indexmaps::mem_layout::c_order(rank)> return_t;
+   return return_t (typename return_t::indexmap_type (mini_vector<size_t,rank>(index...)) , a.storage());
+  }
+
+}}
+
+int main(int argc, char **argv) {
+ triqs::arrays::array<long,1> A = {1,2,3,4,5,6};
+ std::cout << reinterpret_array_view(A, 2,3);
+ return 0;
+}
+
+
+
+
+