From 8cf7465114ae04da1f55ff58d0e181ea5a364dc3 Mon Sep 17 00:00:00 2001
From: Olivier Parcollet <olivier.parcollet@cea.fr>
Date: Tue, 3 Jun 2014 17:16:24 +0200
Subject: [PATCH] C14 : add sequence.

correct seq gcc code inclusion
---
 triqs/utility/c14.hpp | 66 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 65 insertions(+), 1 deletion(-)

diff --git a/triqs/utility/c14.hpp b/triqs/utility/c14.hpp
index c9faa602..c9165cf9 100644
--- a/triqs/utility/c14.hpp
+++ b/triqs/utility/c14.hpp
@@ -23,7 +23,8 @@
 #include <functional>
 #include "./macros.hpp"
 
-// a few that will be C++14, use in advance....
+// backward compat. C++11 compilers.
+// new stuff in 
 
 namespace std { 
  namespace c14 {
@@ -60,6 +61,69 @@ namespace std {
   template<typename T, typename... Args>
    std::unique_ptr<T> make_unique(Args&&... args) { return std::unique_ptr<T>(new T(std::forward<Args>(args)...)); }
 
+  //------------------------------------------------------------------------------------------
+  //
+  // sequence from C++14 : from gcc lib 4.9 
+ /// Class template integer_sequence
+  // Stores a tuple of indices.  Used by tuple and pair, and by bind() to
+  // extract the elements in a tuple.
+  template<size_t... _Indexes>
+    struct _Index_tuple
+    {
+      typedef _Index_tuple<_Indexes..., sizeof...(_Indexes)> __next;
+    };
+
+  // Builds an _Index_tuple<0, 1, 2, ..., _Num-1>.
+  template<size_t _Num>
+    struct _Build_index_tuple
+    {
+      typedef typename _Build_index_tuple<_Num - 1>::__type::__next __type;
+    };
+
+  template<>
+    struct _Build_index_tuple<0>
+    {
+      typedef _Index_tuple<> __type;
+    };
+
+  template<typename _Tp, _Tp... _Idx>
+    struct integer_sequence
+    {
+      typedef _Tp value_type;
+      static constexpr size_t size() { return sizeof...(_Idx); }
+    };
+
+  template<typename _Tp, _Tp _Num,
+	   typename _ISeq = typename _Build_index_tuple<_Num>::__type>
+    struct _Make_integer_sequence;
+
+  template<typename _Tp, _Tp _Num,  size_t... _Idx>
+    struct _Make_integer_sequence<_Tp, _Num, _Index_tuple<_Idx...>>
+    {
+      static_assert( _Num >= 0,
+		     "Cannot make integer sequence of negative length" );
+
+      typedef integer_sequence<_Tp, static_cast<_Tp>(_Idx)...> __type;
+    };
+
+  /// Alias template make_integer_sequence
+  template<typename _Tp, _Tp _Num>
+    using make_integer_sequence
+      = typename _Make_integer_sequence<_Tp, _Num>::__type;
+
+  /// Alias template index_sequence
+  template<size_t... _Idx>
+    using index_sequence = integer_sequence<size_t, _Idx...>;
+
+  /// Alias template make_index_sequence
+  template<size_t _Num>
+    using make_index_sequence = make_integer_sequence<size_t, _Num>;
+
+  /// Alias template index_sequence_for
+  template<typename... _Types>
+    using index_sequence_for = make_index_sequence<sizeof...(_Types)>;
+//--------------------------------------------------
+
  }
 }