Nice idea. How about left parens become +/- by default.
(define rev-append
(lambda (ls1 ls2)
(if (null? ls1)
ls2
(rev-append (cdr ls1) (cons (car ls1) ls2)))))
Mouse over ( at lambda and click:
(define rev-append
(...))
Mouse over ... and you can expand it back.
Can you edit in both modes? -- Matthias