Simple enabling and disabling of overloads

Framework/StackInterface/Stack.h

@@ -15,6 +15,7 @@
 #include <corsika/stack/StackIteratorInterface.h>
 // must be after StackIteratorInterface
 #include <corsika/stack/SecondaryView.h>
+#include <corsika/utl/MetaProgramming.h>
 
 #include <stdexcept>
 #include <type_traits>
@@ -72,11 +73,7 @@ namespace corsika::stack {
      * if StackDataType is a reference member we *HAVE* to initialize
      * it in the constructor, this is typically needed for SecondaryView
      */
-    template <
-        typename _StackDataType = StackDataType,
-        typename = std::enable_if<std::is_same<StackDataType, _StackDataType>::value &&
-                                      std::is_reference<_StackDataType>::value,
-                                  void>>
+    template <typename _ = StackDataType, typename = utl::enable_if<std::is_reference<_>>>
     Stack(StackDataType vD)
         : fData(vD) {}
 
@@ -89,11 +86,8 @@ namespace corsika::stack {
      * stacks, where the inner data container is always a reference
      * and cannot be initialized here.
      */
-    template <
-        typename... Args, typename _StackDataType = StackDataType,
-        typename = std::enable_if<std::is_same<StackDataType, _StackDataType>::value &&
-                                      !std::is_reference<_StackDataType>::value,
-                                  void>>
+    template <typename... Args, typename _ = StackDataType,
+              typename = utl::disable_if<std::is_reference<_>>>
     Stack(Args... args)
         : fData(args...) {}
 

Framework/Utilities/CMakeLists.txt

@@ -28,6 +28,7 @@ set (
   Bit.h
   Singleton.h
   CorsikaFenv.h
+  MetaProgramming.h
   )
 
 set (

Framework/Utilities/MetaProgramming.h

+
+/*
+ * (c) Copyright 2018 CORSIKA Project, corsika-project@lists.kit.edu
+ *
+ * See file AUTHORS for a list of contributors.
+ *
+ * This software is distributed under the terms of the GNU General Public
+ * Licence version 3 (GPL Version 3). See file LICENSE for a full version of
+ * the license.
+ */
+
+#ifndef _include_corsika_utilties_meta_programming_h_
+#define _include_corsika_utilties_meta_programming_h_
+
+#include <type_traits>
+
+/**
+  \file MetaProgramming.h
+
+  Tools to emulate conditional compilation of method overloads.
+
+  ```
+  #include <corsika/utl/MetaProgramming.h>
+
+  template <class T>
+  struct Foo {
+    template <class U, class = corsika::utl::enable_if<std::reference<U>>>
+    void enable_only_if_U_is_reference(U x) {}
+
+    template <class _ = T, class = corsika::utl::disable_if<std::reference<_>>>
+    void enable_only_if_T_is_not_reference() {}
+  };
+  ```
+
+  To combine traits, use boost::mp11::mp_and or boost::mp11::mp_or.
+
+  ```
+  #include <corsika/utl/MetaProgramming.h>
+  #include <boost/mp11.hpp>
+
+  template <class T>
+  struct Foo {
+    template <class U, class = corsika::utl::enable_if<
+      boost::mp11::mp_and<std::is_reference<T>, std::is_const<T>>
+    >
+    void enable_only_if_U_is_const_reference(U x) {}
+  };
+  ```
+
+  Common combined traits may be implemented in this header. For example:
+  ```
+  template <class T>
+  using is_cref = boost::mp11::mp_and<std::is_reference<T>, std::is_const<T>>;
+  ```
+}
+*/
+
+namespace corsika::utl {
+  template <class Trait>
+  using enable_if = typename std::enable_if<(Trait::value == true)>::type;
+
+  template <class Trait>
+  using disable_if = typename std::enable_if<(Trait::value == false)>::type;
+} // namespace corsika::utl
+
+#endif