is-selected? in list-box%

Returns #t if the item matching the specifies index is selected, #f otherwise.

A list box's selection can be changed by the user clicking the control, and such changes do not go through this method; use the control callback procedure (provided as an initialization argument) to monitor selection changes.

• (send a-list-box is-selected? n) -> boolean
     n : exact non-negative integer

  Returns #t if the item index by n is selected. List box items are indexed from 0. If n is equal to or larger than the number of choices, an exn:fail:contract exception is raised.