From 02675d8c66bad7540d81e83d6c2ecfd7730be8a6 Mon Sep 17 00:00:00 2001
From: Eduard Valeyev <eduard@valeyev.net>
Date: Mon, 28 Jul 2014 09:58:19 -0400
Subject: [PATCH] Added provisional implementation of C++14's
 cbegin/cend/rbegin/rend

---
 btas/array_adaptor.h         | 72 ++++++++++--------------------------
 btas/util/sequence_adaptor.h |  5 ---
 2 files changed, 20 insertions(+), 57 deletions(-)

diff --git a/btas/array_adaptor.h b/btas/array_adaptor.h
index 25011eef..8cd501ec 100644
--- a/btas/array_adaptor.h
+++ b/btas/array_adaptor.h
@@ -139,58 +139,7 @@ namespace btas {
 namespace std {
 
   template <typename T, size_t N>
-  auto cbegin(const std::array<T,N>& x) -> decltype(x.cbegin()) {
-    return x.cbegin();
-  }
-  template <typename T, size_t N>
-  auto cend(const std::array<T,N>& x) -> decltype(x.cend()) {
-    return x.cend();
-  }
-  template <typename T, size_t N>
-  auto rbegin(std::array<T,N>& x) -> decltype(x.rbegin()) {
-    return x.rbegin();
-  }
-  template <typename T, size_t N>
-  auto rend(std::array<T,N>& x) -> decltype(x.rend()) {
-    return x.rend();
-  }
-
-  template <typename T>
-  auto cbegin(const btas::varray<T>& x) -> decltype(x.cbegin()) {
-    return x.cbegin();
-  }
-  template <typename T>
-  auto cend(const btas::varray<T>& x) -> decltype(x.cend()) {
-    return x.cend();
-  }
-  template <typename T>
-  auto rbegin(btas::varray<T>& x) -> decltype(x.rbegin()) {
-    return x.rbegin();
-  }
-  template <typename T>
-  auto rend(btas::varray<T>& x) -> decltype(x.rend()) {
-    return x.rend();
-  }
-
-  template <typename T>
-  auto cbegin(const std::vector<T>& x) -> decltype(x.cbegin()) {
-    return x.cbegin();
-  }
-  template <typename T>
-  auto cend(const std::vector<T>& x) -> decltype(x.cend()) {
-    return x.cend();
-  }
-  template <typename T>
-  auto rbegin(std::vector<T>& x) -> decltype(x.rbegin()) {
-    return x.rbegin();
-  }
-  template <typename T>
-  auto rend(std::vector<T>& x) -> decltype(x.rend()) {
-    return x.rend();
-  }
-
-  template <typename T, size_t N>
-  const T* cbegin(const T (&x)[N]) {
+  const T* cbegin(const T(&x)[N]) {
     return &x[0];
   }
   template <typename T, size_t N>
@@ -219,6 +168,25 @@ namespace std {
     return x;
   }
 
+#if __cplusplus == 201103L // add useful bits to make transition to C++14 easier
+  template <typename C>
+  constexpr auto cbegin(const C& x) -> decltype(std::begin(x)) {
+    return std::begin(x);
+  }
+  template <typename C>
+  constexpr auto cend(const C& x) -> decltype(std::end(x)) {
+    return std::end(x);
+  }
+  template <typename C>
+  auto rbegin(C& x) -> decltype(x.rbegin()) {
+    return x.rbegin();
+  }
+  template <typename C>
+  auto rend(C& x) -> decltype(x.rend()) {
+    return x.rend();
+  }
+#endif
+
   template <typename T>
   struct make_unsigned<std::vector<T> > {
       typedef std::vector<typename make_unsigned<T>::type > type;
diff --git a/btas/util/sequence_adaptor.h b/btas/util/sequence_adaptor.h
index 9e30a35d..ceb859fb 100644
--- a/btas/util/sequence_adaptor.h
+++ b/btas/util/sequence_adaptor.h
@@ -122,11 +122,6 @@ namespace std {
       return reference_wrapper<const btas::infinite_sequence_adaptor<_T*>>(t);
   }
 
-  template <typename T>
-  auto cbegin(const btas::infinite_sequence_adaptor<T>& x) -> decltype(x.cbegin()) {
-    return x.cbegin();
-  }
-
 }
 
 #endif /* __BTAS_UTIL_SEQUENCEADAPTOR_H_ */