delete in list-box%

Deletes a choice from the list box. Selected items that are not deleted remain selected, and no other items are selected.

• (send a-list-box delete n) -> void
     n : exact non-negative integer

  Deletes the item indexed by n. List box items are indexed from 0. If n is equal to or larger than the number of items in the control, an exn:fail:contract exception is raised.