Allowing backward 1D from RNN

Author: castelao

src/nf/nf_layer_submodule.f90

@@ -49,6 +49,19 @@ pure module subroutine backward_1d(self, previous, gradient)
             call this_layer % backward(prev_layer % output, gradient)
         end select
 
+      type is(rnn_layer)
+
+        select type(prev_layer => previous % p)
+          type is(input1d_layer)
+            call this_layer % backward(prev_layer % output, gradient)
+          type is(dense_layer)
+            call this_layer % backward(prev_layer % output, gradient)
+          type is(flatten_layer)
+            call this_layer % backward(prev_layer % output, gradient)
+          type is(rnn_layer)
+            call this_layer % backward(prev_layer % output, gradient)
+        end select
+
     end select
 
   end subroutine backward_1d