diff --git a/test/triqs/gfs/gf_2times.cpp b/test/triqs/gfs/gf_2times.cpp
index be590bee..cacfcb32 100644
--- a/test/triqs/gfs/gf_2times.cpp
+++ b/test/triqs/gfs/gf_2times.cpp
@@ -37,7 +37,7 @@ int main() {
  auto zz = G_w_wn2(t_,tp_);
  //std::cout  << std::get<0>(zz.childs).data() << std::endl ;
  auto yy = eval ( zz, t_=2, tp_=3);
- std::cout  << yy.indexmap()<< std::endl ;
+ //std::cout  << yy.indexmap()<< std::endl ;
  std::cout  << yy << std::endl ;
  //std::cout  << eval ( zz, t_=2, tp_=3)<< std::endl ;
  //std::cout  << eval ( G_w_wn2(t_,tp_), t_=2, tp_=3)<< std::endl ;
diff --git a/triqs/arrays/matrix_tensor_proxy.hpp b/triqs/arrays/matrix_tensor_proxy.hpp
index 99e02747..8bd90e1b 100644
--- a/triqs/arrays/matrix_tensor_proxy.hpp
+++ b/triqs/arrays/matrix_tensor_proxy.hpp
@@ -35,7 +35,7 @@ namespace arrays {
  // tensor const
  template <typename A, bool IsMatrix>
  struct const_matrix_tensor_proxy : std::conditional<IsMatrix, TRIQS_CONCEPT_TAG_NAME(ImmutableMatrix),
-                                                     TRIQS_CONCEPT_TAG_NAME(ImmutableCuboidArray)>::type {
+                                                     TRIQS_CONCEPT_TAG_NAME(ImmutableArray)>::type {
 
   typedef typename std::remove_reference<A>::type A_t;
   static constexpr bool is_const = true;
@@ -84,7 +84,7 @@ namespace arrays {
  // tensor no const
  template <typename A, bool IsMatrix>
  struct matrix_tensor_proxy : std::conditional<IsMatrix, TRIQS_CONCEPT_TAG_NAME(MutableMatrix),
-                                               TRIQS_CONCEPT_TAG_NAME(MutableCuboidArray)>::type {
+                                               TRIQS_CONCEPT_TAG_NAME(MutableArray)>::type {
 
   typedef typename std::remove_reference<A>::type A_t;
   static constexpr bool is_const = false;
diff --git a/triqs/gfs/imfreq.hpp b/triqs/gfs/imfreq.hpp
index a9f723f1..f1f7e558 100644
--- a/triqs/gfs/imfreq.hpp
+++ b/triqs/gfs/imfreq.hpp
@@ -55,10 +55,14 @@ namespace gfs {
   // simple evaluation : take the point on the grid...
   template <> struct evaluator_fnt_on_mesh<imfreq> {
    long n;
+   double w;
    evaluator_fnt_on_mesh() = default;
-   template <typename MeshType> evaluator_fnt_on_mesh(MeshType const &m, long p) { n = p; }
-   template <typename MeshType> evaluator_fnt_on_mesh(MeshType const &m, matsubara_freq const &p) { n = p.n; }
-   template <typename F> auto operator()(F const &f) const DECL_AND_RETURN(f(n));
+   template <typename MeshType> evaluator_fnt_on_mesh(MeshType const &m, long p) { n = p; w=1; } 
+   template <typename MeshType> evaluator_fnt_on_mesh(MeshType const &m, matsubara_freq const &p) { 
+    if ((p.n >= m.index_start()) && (p.n < m.size()+m.index_start())) {w=1; n =p.n;}
+    else {w=0; n=0;}
+   }
+   template <typename F> auto operator()(F const &f) const DECL_AND_RETURN(w*f(n));
   };
 
   // ------------- evaluator  -------------------
diff --git a/triqs/gfs/meshes/matsubara_freq.hpp b/triqs/gfs/meshes/matsubara_freq.hpp
index 617e6685..234410b4 100644
--- a/triqs/gfs/meshes/matsubara_freq.hpp
+++ b/triqs/gfs/meshes/matsubara_freq.hpp
@@ -69,6 +69,9 @@ namespace gfs {
   /// Flatten the index in the positive linear index for memory storage (almost trivial here).
   long index_to_linear(index_t ind) const { return ind - index_start(); }
 
+  /// Is the mesh only for positive omega_n (G(tau) real))
+  bool positive_only() const { return _positive_only;}
+
   /**
    *  The mesh point
    *