Improved the add_layer forwarding constructor. Also added repeat_group()

variable decorator.

dlib/dnn/core.h

@@ -596,6 +596,16 @@ namespace dlib
         };
         template <typename ...T, typename ...U>
         struct disable_forwarding_constr<std::tuple<T...>,U...>
+        {
+            const static bool value = disable_forwarding_constr<typename std::remove_reference<T>::type...>::value;
+        };
+        template <typename T, typename ...U>
+        struct disable_forwarding_constr<std::tuple<T>,U...>
+        {
+            const static bool value = disable_forwarding_constr<typename std::remove_reference<T>::type>::value;
+        };
+        template <typename ...U>
+        struct disable_forwarding_constr<std::tuple<>,U...>
         {
             const static bool value = true;
         };
@@ -658,6 +668,10 @@ namespace dlib
             T&& ...args
         ) : add_layer(layer_det,args...) { }
 
+        add_layer (
+            std::tuple<>
+        ) : add_layer() {}
+
         template <typename ...T>
         add_layer(
             std::tuple<>, 
@@ -1374,6 +1388,23 @@ namespace dlib
         };
     }
 
+    template <typename ...T>
+    struct decorator_repeat_group
+    {
+        decorator_repeat_group(
+            T&& ...args
+        ) : data(std::forward<T>(args)...) {}
+
+        std::tuple<T...> data;
+    };
+    template <typename ...T>
+    decorator_repeat_group<T...> repeat_group (
+        T&& ...args
+    )
+    {
+        return decorator_repeat_group<T...>(std::forward<T>(args)...);
+    }
+
     template <
         size_t num,
         template<typename> class REPEATED_LAYER, 
@@ -1440,6 +1471,16 @@ namespace dlib
         {
         }
 
+        template <typename ...T, typename ...U>
+        repeat(
+            decorator_repeat_group<T...>&& arg1,
+            U ...args2
+        ): 
+            details(num, arg1.data),
+            subnetwork(std::move(args2)...)
+        {
+        }
+
         template <typename T, typename ...U>
         repeat(
             std::tuple<>,

dlib/dnn/core_abstract.h

@@ -963,6 +963,17 @@ namespace dlib
 // ----------------------------------------------------------------------------------------
 // ----------------------------------------------------------------------------------------
 
+    template <typename ...T>
+    decorator_repeat_group<T...> repeat_group (
+        T&& ...args
+    );
+    /*!
+        ensures
+            - Decorates a group of variables.  This is essentially like std::make_tuple()
+              except it's only purpose is to group variables together so they can be passed
+              to the repeat object's constructor.
+    !*/
+
     template <
         size_t num,
         template<typename> class REPEATED_LAYER, 
@@ -1020,6 +1031,20 @@ namespace dlib
                   SUBNET's constructor.  
         !*/
 
+        template <typename ...T, typename ...U>
+        repeat(
+            decorator_repeat_group<T...>&& arg1,
+            U ...args2
+        );
+        /*!
+            ensures
+                - arg1 is used to initialize the num_repetitions() copies of REPEATED_LAYER inside
+                  this object.  That is, all the REPEATED_LAYER elements are initialized identically
+                  by being given copies of an undecorated arg1.
+                - The rest of the arguments to the constructor, i.e. args2, are passed to
+                  SUBNET's constructor.  
+        !*/
+
         size_t num_repetitions (
         ) const; 
         /*!