Updated a comment.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403907

dlib/is_kind.h

@@ -49,7 +49,7 @@ namespace dlib
     struct is_matrix : public default_is_kind_value  
     {
         /*!
-            - if (T is some kind of matrix expression from the matrix/matrix_abstract.h component) then
+            - if (T is some kind of matrix expression from the matrix/matrix_exp_abstract.h component) then
                 - is_matrix<T>::value == true
             - else
                 - is_matrix<T>::value == false