diff --git a/test/triqs/arrays/const_view.cpp b/test/triqs/arrays/const_view.cpp
new file mode 100644
index 00000000..a4786e34
--- /dev/null
+++ b/test/triqs/arrays/const_view.cpp
@@ -0,0 +1,41 @@
+/*******************************************************************************
+ *
+ * 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 "./common.hpp"
+#include "./src/array.hpp"
+#include <iostream>
+
+using namespace triqs::arrays;
+
+int main(int argc, char **argv) {
+
+ const array<long,1> A = {1,2,3,4};
+
+ std::cerr  << A.opt_flags<<std::endl;
+ std::cerr  << A().opt_flags<<std::endl;
+
+ // None of this should compile
+ //A(0) = 2;
+ //A()(0) = 2;
+ //A(range(0,2))(0) = 10;
+
+ return 0;
+}
+
diff --git a/test/triqs/arrays/temp_slice.cpp b/test/triqs/arrays/temp_slice.cpp
new file mode 100644
index 00000000..7887307b
--- /dev/null
+++ b/test/triqs/arrays/temp_slice.cpp
@@ -0,0 +1,78 @@
+/*******************************************************************************
+ *
+ * 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 "./common.hpp"
+#include "./src/array.hpp"
+#include <iostream>
+
+using namespace triqs::arrays;
+
+auto bad (array<long,1> const & a) DECL_AND_RETURN (a(range(0,3))); 
+
+auto bad2 (array<long,1> const & a) DECL_AND_RETURN (a(0)); 
+
+array_view<long,1> good(array<long,1> const & a) {return a(range(0,3));}
+
+
+int main(int argc, char **argv) {
+
+ try { 
+
+  array<long,1> A = {1,2,3,4};
+
+  std::cerr<<"A is "<<A<<std::endl;
+
+  {
+   auto r = A(range(0,3));
+   TEST_ASSERT(r.storage().is_weak);
+  }
+
+  {
+   auto r = array<long,1> {1,2,3,4} (range(0,3));
+   TEST_ASSERT(!r.storage().is_weak);
+   std::cerr  << r << r.storage().is_weak << std::endl ;
+  }
+
+  {
+   auto r = array<long,1> {1,2,3,4} (range(0,3))();
+   std::cerr  << r << r.storage().is_weak << std::endl ;
+   TEST_ASSERT(!r.storage().is_weak);
+  }
+
+  {
+   auto r = good ( { 1,2,3,4} );
+   std::cerr  << " good "<< r << r.storage().is_weak << std::endl ;
+  }
+
+  {
+   auto & r = bad2 ( { 1,2,3,4} );
+   std::cerr  << " bad2 " << r << std::endl ;
+  }
+
+  {
+   auto r = bad ( { 1,2,3,4} );
+   std::cerr  << " bad " << r << r.storage().is_weak << std::endl ;
+  }
+
+ }
+ catch (std::exception & e) { std::cout << e.what()<<std::endl;}
+ return 0;
+}
+
diff --git a/triqs/arrays/impl/common.hpp b/triqs/arrays/impl/common.hpp
index 6404b65f..53648a36 100644
--- a/triqs/arrays/impl/common.hpp
+++ b/triqs/arrays/impl/common.hpp
@@ -55,13 +55,14 @@ namespace boost { namespace serialization { class access;}}
 
 #define TRIQS_ARRAYS_ENFORCE_BOUNDCHECK
 #define TRIQS_ARRAYS_CHECK_IM_STORAGE_COMPAT
+#define TRIQS_ARRAYS_CHECK_WEAK_REFS
 
 #else 
 #define TRIQS_ARRAYS_DEBUG_CHECK(Cond,Error) 
 #endif
 
 // In particular, gcc 4.6, 4.7 do not have "rvalue for *this", which forbid the implementation 
-// of weak references. In that we, we will revert to strong view instead. 
+// of weak references. In that case, we will revert to strong view instead. 
 #ifdef TRIQS_COMPILER_IS_OBSOLETE
 #define TRIQS_ARRAYS_SLICE_DEFAUT_IS_SHARED
 #endif
diff --git a/triqs/arrays/impl/flags.hpp b/triqs/arrays/impl/flags.hpp
index d94c8add..ef79c4e4 100644
--- a/triqs/arrays/impl/flags.hpp
+++ b/triqs/arrays/impl/flags.hpp
@@ -27,18 +27,18 @@ namespace triqs { namespace arrays {
 
  // Flags is a 64 bit unsigned int.
  // 0 is the default option.
- // Meaning of the bits : 
- // 0   -> Boundcheck
+ // Meaning of the bits :
+ // 0   -> Const
  // 1,2 -> Predefined order : 
  //    0 : None, 1 : C, 2 : Fortran 
- // 3,4 -> Init 
- //    0 : Noinit, 1 : NanInit, 2 : DefaultInit
+ // 3 -> Init the array 
+ // 5 -> Boundcheck
 
- constexpr ull_t BoundCheck   = 1ull << 0;
- constexpr ull_t TraversalOrderC       = 1ull << 1;
- constexpr ull_t TraversalOrderFortran = 1ull << 2;
- //constexpr ull_t NanInit      = 1ull << 3;
- constexpr ull_t DefaultInit  = 1ull << 4;
+ constexpr ull_t ConstView              = 1ull << 0;
+ constexpr ull_t TraversalOrderC        = 1ull << 1;
+ constexpr ull_t TraversalOrderFortran  = 1ull << 2;
+ constexpr ull_t DefaultInit            = 1ull << 3;
+ constexpr ull_t BoundCheck             = 1ull << 5;
 
 #define BOUND_CHECK              triqs::arrays::BoundCheck
 #define TRAVERSAL_ORDER_C        triqs::arrays::TraversalOrderC
@@ -55,10 +55,12 @@ namespace triqs { namespace arrays {
   constexpr ull_t get(ull_t f, ull_t a)   { return  ((f & (1ull<<a)) >> a);}
   constexpr ull_t get2(ull_t f, ull_t a)  { return  ((f & ((1ull<<a) + (1ull<< (a+1ull)))) >> a);}
 
+  constexpr bool is_const (ull_t f) { return get (f,0) !=0;}
+
 #ifdef TRIQS_ARRAYS_ENFORCE_BOUNDCHECK
   constexpr bool bound_check      (ull_t f) { return true;}
 #else
-  constexpr bool bound_check      (ull_t f) { return get (f, 0)!=0;}
+  constexpr bool bound_check      (ull_t f) { return get (f, 5)!=0;}
 #endif
 
   constexpr bool traversal_order_c         (ull_t f) { return get (f,1ull)!=0ull;}
@@ -66,13 +68,11 @@ namespace triqs { namespace arrays {
 
   template< ull_t F> struct bound_check_trait { static constexpr bool value = bound_check(F); }; 
 
-  constexpr ull_t init_mode        (ull_t f) { return get2 (f,3);}
-  constexpr bool check_init_mode   (ull_t f) { return get2 (f,3)!=3ull;}
+  constexpr ull_t init_mode        (ull_t f) { return get (f,3);}
 
   template<ull_t F> struct init_tag1;
   template<> struct init_tag1<0> { typedef Tag::no_init type;};
-  //template<> struct init_tag1<1> { typedef Tag::nan_inf_init type;};
-  template<> struct init_tag1<2> { typedef Tag::default_init type;};
+  template<> struct init_tag1<1> { typedef Tag::default_init type;};
 
   // for the init_tag, we pass the *whole* option flag.
   template<ull_t F> struct init_tag : init_tag1 < init_mode(F)> {};
@@ -81,21 +81,21 @@ namespace triqs { namespace arrays {
    static constexpr bool bc = bound_check(F);
    static constexpr bool is_c = traversal_order_c(F);
    static constexpr bool is_f = traversal_order_fortran(F);
-   static constexpr bool inm = check_init_mode(F);
    static_assert ( (!( is_c && is_f)), "You asked C and Fortran traversal order at the same time...");
    static_assert ( (!( (is_c || is_f) && To )), "You asked C or Fortran traversal order and gave a traversal order ...");
-   static_assert ( (inm), "You asked nan and default init at the same time...");
   };
 
 #else 
 
 #define TRIQS_FLAGS_GET(f,a) ((f & (1ull<<a)) >> a)
 #define TRIQS_FLAGS_GET2(f,a) ((f & ((1ull<<a) + (1ull<< (a+1ull)))) >> a) 
- 
+
+  constexpr bool is_const (ull_t f) { return false;} // non const view on icc 
+
 #ifdef TRIQS_ARRAYS_ENFORCE_BOUNDCHECK
   template< ull_t F> struct bound_check_trait { static constexpr bool value = true;};
 #else
-  template< ull_t F> struct bound_check_trait { static constexpr bool value = TRIQS_FLAGS_GET (F, 0)!=0; }; 
+  template< ull_t F> struct bound_check_trait { static constexpr bool value = TRIQS_FLAGS_GET (F, 5)!=0; }; 
 #endif
   
   template< ull_t F> struct traversal_order_c { static constexpr bool value = TRIQS_FLAGS_GET(F,1) !=0; };
@@ -105,8 +105,7 @@ namespace triqs { namespace arrays {
 
   template<ull_t F> struct init_tag1;
   template<> struct init_tag1<0> { typedef Tag::no_init type;};
-  //template<> struct init_tag1<1> { typedef Tag::nan_inf_init type;};
-  template<> struct init_tag1<2> { typedef Tag::default_init type;};
+  template<> struct init_tag1<1> { typedef Tag::default_init type;};
   template<ull_t F> struct init_tag : init_tag1 < init_mode_tr<F>::value > {};
 
   template<ull_t F, ull_t To> struct assert_make_sense { };// no check on icc
diff --git a/triqs/arrays/impl/indexmap_storage_pair.hpp b/triqs/arrays/impl/indexmap_storage_pair.hpp
index b06b7a56..0551f436 100644
--- a/triqs/arrays/impl/indexmap_storage_pair.hpp
+++ b/triqs/arrays/impl/indexmap_storage_pair.hpp
@@ -52,6 +52,7 @@ namespace triqs { namespace arrays {
     typedef StorageType storage_type;
     typedef IndexMapType indexmap_type;
     static constexpr unsigned int rank = IndexMapType::domain_type::rank;
+    static constexpr ull_t opt_flags = OptionFlags;
    protected:
 
     indexmap_type indexmap_;
@@ -188,7 +189,7 @@ namespace triqs { namespace arrays {
     // Evaluation and slices
     template<typename... Args>
      typename std::enable_if<
-     (!clef::is_any_lazy<Args...>::value) && (indexmaps::slicer<indexmap_type,Args...>::r_type::domain_type::rank==0)
+     (!clef::is_any_lazy<Args...>::value) && (indexmaps::slicer<indexmap_type,Args...>::r_type::domain_type::rank==0) && !flags::is_const(OptionFlags)
      , value_type &>::type
      operator()(Args const & ... args) {  return storage_[indexmap_(args...)]; }
 
@@ -203,7 +204,8 @@ namespace triqs { namespace arrays {
      //typedef typename std::conditional<is_const, typename std::add_const<value_type>::type, value_type>::type V2;
      typedef value_type V2;
      static_assert(IM2::domain_type::rank !=0, "Internal error");
-     typedef typename ISPViewType<V2,IM2::domain_type::rank, OptionFlags, IM2::traversal_order_in_template, ViewTag, ForceBorrowed || StorageType::is_weak >::type type;
+     static constexpr ull_t optmodif = (is_const ? ConstView : 0ull);
+     typedef typename ISPViewType<V2,IM2::domain_type::rank, OptionFlags|optmodif, IM2::traversal_order_in_template, ViewTag, ForceBorrowed || StorageType::is_weak >::type type;
     };
 
 // change here only for debug
@@ -211,7 +213,7 @@ namespace triqs { namespace arrays {
 #ifndef TRIQS_ARRAYS_SLICE_DEFAUT_IS_SHARED
     template<typename... Args>   // non const version
      typename boost::lazy_enable_if_c<
-     (!clef::is_any_lazy<Args...>::value) && (indexmaps::slicer<indexmap_type,Args...>::r_type::domain_type::rank!=0)
+     (!clef::is_any_lazy<Args...>::value) && (indexmaps::slicer<indexmap_type,Args...>::r_type::domain_type::rank!=0) && !flags::is_const(OptionFlags) 
      , result_of_call_as_view<false,true,Args...>
      >::type // enable_if
      operator()(Args const & ... args) & {
@@ -236,8 +238,7 @@ namespace triqs { namespace arrays {
      }
 
     /// Equivalent to make_view
-    //typename ISPViewType<typename std::add_const<value_type>::type,domain_type::rank, OptionFlags, TraversalOrder, ViewTag >::type
-    typename ISPViewType<value_type,domain_type::rank, OptionFlags, TraversalOrder, ViewTag, true >::type
+    typename ISPViewType<value_type,domain_type::rank, OptionFlags | ConstView, TraversalOrder, ViewTag, true >::type
      operator()() const & { return *this; }
     
     typename ISPViewType<value_type,domain_type::rank, OptionFlags, TraversalOrder, ViewTag, true >::type
diff --git a/triqs/utility/compiler_details.hpp b/triqs/utility/compiler_details.hpp
index 9967b67f..686bad0b 100644
--- a/triqs/utility/compiler_details.hpp
+++ b/triqs/utility/compiler_details.hpp
@@ -21,13 +21,16 @@
 #ifndef TRIQS_COMPILER_DETAILS_H
 #define TRIQS_COMPILER_DETAILS_H
 
-#ifdef __GNUC__
+#if defined __GNUC__  ||  defined  __clang__
 #define restrict __restrict__
+#endif
 
+#if defined __GNUC__  && ! defined  __clang__
 #define GCC_VERSION (__GNUC__ * 10000 \
                                + __GNUC_MINOR__ * 100 \
                                + __GNUC_PATCHLEVEL__)
 #if GCC_VERSION < 40801
+#warning "gcc compiler" GCC_VERSION
 #define TRIQS_COMPILER_IS_OBSOLETE
 // we still accept gcc 4.6 and 4.7, but only the 4.8.1 and higher is a compliant c++11
 #endif