cleanup GaudiKernel/reverse.h

• move implementation details into details namespace
• drop gcc 4.9 backwards compatibility hack
• add test case

GaudiKernel/GaudiKernel/reverse.h

@@ -22,51 +22,36 @@
 //  implies that it does meet the requirements for aggregate initializaton,
 //  which allows for {} initialization of its member.
 //
-#include <utility>
 
+#include <iterator>
 #include <utility>
 
-template <typename Iterable>
-struct reverse_wrapper {
-  Iterable iterable;
-};
-
-template <typename T>
-reverse_wrapper<T> reverse( T&& iterable )
+namespace details
 {
-  return {std::forward<T>( iterable )};
-}
-
-#if defined __GNUC__ && __GNUC__ < 5
 
-// std::rbegin and std::rend require gcc 5.0 or later (or clang 3.5 or later)
-template <typename T>
-auto begin( reverse_wrapper<T>& w ) -> decltype( w.iterable.rbegin() )
-{
-  return w.iterable.rbegin();
-}
-template <typename T>
-auto end( reverse_wrapper<T>& w ) -> decltype( w.iterable.rend() )
-{
-  return w.iterable.rend();
+  template <typename Iterable>
+  struct reverse_wrapper {
+    Iterable iterable;
+  };
+
+  template <typename T>
+  auto begin( reverse_wrapper<T>& w )
+  {
+    using std::rbegin;
+    return rbegin( w.iterable );
+  }
+  template <typename T>
+  auto end( reverse_wrapper<T>& w )
+  {
+    using std::rend;
+    return rend( w.iterable );
+  }
 }
 
-#else
-
-#include <iterator>
-template <typename T>
-auto begin( reverse_wrapper<T>& w )
-{
-  using std::rbegin;
-  return rbegin( w.iterable );
-}
 template <typename T>
-auto end( reverse_wrapper<T>& w )
+details::reverse_wrapper<T> reverse( T&& iterable )
 {
-  using std::rend;
-  return rend( w.iterable );
+  return {std::forward<T>( iterable )};
 }
 
 #endif
-
-#endif