diff --git a/dlib/dnn/tensor.h b/dlib/dnn/tensor.h
index 7c4d03b00..1a1a6ce6d 100644
--- a/dlib/dnn/tensor.h
+++ b/dlib/dnn/tensor.h
@@ -191,6 +191,18 @@ namespace dlib
         long m_size; // always equal to m_n*m_k*m_nr*m_nc
     };
 
+// ----------------------------------------------------------------------------------------
+
+    inline bool is_vector (
+        const tensor& t
+    )
+    {
+        return t.size() == t.num_samples() ||
+               t.size() == t.k() ||
+               t.size() == t.nr() ||
+               t.size() == t.nc();
+    }
+
 // ----------------------------------------------------------------------------------------
 
     inline const matrix_op<op_pointer_to_mat<float> > mat (
diff --git a/dlib/dnn/tensor_abstract.h b/dlib/dnn/tensor_abstract.h
index f90a9d2fd..79ec054dd 100644
--- a/dlib/dnn/tensor_abstract.h
+++ b/dlib/dnn/tensor_abstract.h
@@ -345,6 +345,20 @@ namespace dlib
             - This function blocks until the copy has completed.
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    bool is_vector (
+        const tensor& t
+    );
+    /*!
+        ensures
+            - returns true if and only if one of the following is true:
+                - t.size() == t.num_samples() 
+                - t.size() == t.k() 
+                - t.size() == t.nr() 
+                - t.size() == t.nc()
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     const matrix_exp mat (