A couple of notes.

Website: Changed

CCS Github is a jerkface.

Gradescope Grading Scale: Updated phrasing

Now phrases should better reflect what you’re seeing.

Canvas Grading Scale

Now 0-9.

Racket’s match

Cf.

##

Arithmetic examples.

plus

times

expt

Generalizing

This is not news.

  • Wilhelm Ackermann
  • Gabriel Sudan
(define (phi p m n)
  (cond
    [(zero? p) (+ m n)]
    [(and (zero? n) (zero? (sub1 p))) 0]
    [(and (zero? n) (zero? (sub1 (sub1 p)))) 1]
    [(zero? n) m]
    [else (phi (sub1 p) m (phi p m (sub1 n)))]))

After Ackermann’s publication of his function (which had three nonnegative integer arguments), many authors modified it to suit various purposes, so that today “the Ackermann function” may refer to any of numerous variants of the original function. One common version, the two-argument Ackermann–Péter function, is defined as follows for nonnegative integers m and n:

– wiki

(define (ack-peter m n)
  (cond
    [(zero? m) (add1 n)]
    [(zero? n) (ack-peter (sub1 m) 1)]
    [else (ack-peter (sub1 m) (ack-peter m (sub1 n)))]))

Updated: