Added visit_layers()

dlib/dnn/core.h

@@ -3198,6 +3198,57 @@ namespace dlib
         impl::vlpg_loop<0, net_type::num_layers>::visit(comp_i, net, v);
     }
 
+// ----------------------------------------------------------------------------------------
+
+    namespace impl
+    {
+        template <size_t i, size_t num>
+        struct vl_loop
+        {
+            template <
+                typename net_type,
+                typename visitor
+                >
+            static void visit(
+                net_type& net,
+                visitor&& v
+            )
+            {
+                v(i, layer<i>(net));
+                vl_loop<i+1, num>::visit(net,v);
+            }
+        };
+
+        template <size_t num>
+        struct vl_loop<num,num>
+        {
+            template <
+                typename net_type,
+                typename visitor
+                >
+            static void visit(
+                net_type&,
+                visitor&& 
+            )
+            {
+                // Base case of recursion.  Don't do anything.
+            }
+        };
+
+    }
+
+    template <
+        typename net_type,
+        typename visitor
+        >
+    void visit_layers(
+        net_type& net,
+        visitor v
+    )
+    {
+        impl::vl_loop<0, net_type::num_layers>::visit(net, v);
+    }
+
 // ----------------------------------------------------------------------------------------
 
 }

dlib/dnn/core_abstract.h

@@ -1425,6 +1425,32 @@ namespace dlib
             - When v() is called, the first argument is always < net_type::num_computational_layers.
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename net_type,
+        typename visitor
+        >
+    void visit_layers(
+        net_type& net,
+        visitor v
+    );
+    /*!
+        requires
+            - net_type is an object of type add_layer, add_loss_layer, add_skip_layer, or
+              add_tag_layer.
+            - v is a function object with a signature equivalent to: 
+                v(size_t idx, any_net_type& t)
+              That is, it must take a size_t and then any of the network types such as
+              add_layer, add_loss_layer, etc.
+        ensures
+            - Loops over all the layers in net and calls v() on them.  To be specific, this
+              function essentially performs the following:
+
+                for (size_t i = 0; i < net_type::num_layers; ++i)
+                    v(i, layer<i>(net));
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     struct layer_test_results