git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@2514 
c3d73ce0-8a6f-49c7-b76d-
6d57e0e08775
         else {
             if ( current.Len() == 1 ) {
                 // it's a letter
-                keyCode = wxToupper(current[0]);
+                keyCode = wxToupper(current[0U]);
             }
             else {
                 // it should be a function key
-                if ( current[0] == 'f' && isdigit(current[1]) &&
+                if ( current[0U] == 'f' && isdigit(current[1U]) &&
                      (current.Len() == 2 ||
-                     (current.Len() == 3 && isdigit(current[2]))) ) {
+                     (current.Len() == 3 && isdigit(current[2U]))) ) {
                     int n;
                     sscanf(current.c_str() + 1, "%d", &n);