[Chicken-users] Q:Meaning of [ ] in the bb notes example?

[Michael Erdmann]

Hallo,

what is the meaning of the [ ] in the let statement od the notes example
in bb extension.
In docu (sect. 5.2) it is mentioned as an alternative for ( ). But why 
has been used?

(define (change-title)
  (let ([i (bb:property item-list 'value)])
    (when (> i 0)
      (let* ([note (list-ref all-notes (sub1 i))]
             [title (bb:get-input "Enter new title" (note-title note))] )
        (set! (bb:property (note-window note) 'text) title)
        (note-title-set! note title)
        (update-list) ) ) ) )   



Regards
   M.Erdmann