Question

In scheme, it is possible to use set! to create two (or more) functions which share a private scope between them:

(define f1 #f) ; or any other "undefined" value
(define f2 #f)

(let ((private some-value) (another-private some-other-value))
  (set! f1 (lambda ... <use of private variables> ...))
  (set! f2 (lambda ... <use of private variables> ...)))

or by using a third variable:

(define functions
  (let ((private some-value) (another-private some-other-value))
    (list (lambda ... <use of private variables> ...)
          (lambda ... <use of private variables> ...))))

(define f1 (car functions))
(define f2 (cadr functions))

However, both of these seem inelegant, due to the use of set! in the first and the left-over variable functions in the second. Is there a way to do this without either?

Answer 1

(define-values (f1 f2)
  (let ((private values) ...)
    (values (lambda ...)
            (lambda ...))))