let ask_for_lval (main_ui:Design.main_window_extension_points) kf stmt =
let txt = GToolbox.input_string ~title:"Input lvalue expression" "" in
match txt with None | Some "" -> None
| Some txt ->
try
let term_lval = !Db.Properties.Interp.lval kf stmt txt in
let lval = !Db.Properties.Interp.term_lval_to_lval term_lval in
Some (txt, lval)
with e ->
main_ui#error "[ask for lval] '%s' invalid expression: %s@."
txt (Printexc.to_string e);
None