Hyperoperators

gistfile1.rkt

#lang racket
(provide (all-defined-out))

(define (hyper n)
  (cond
   ;; [(= n 0) add1]
   [(= n 1) +]
   [(= n 2) *]
   [else (lambda (base r)
           (foldl (hyper (sub1 n))
                  1
                  (make-list r base)))]))

(equal? ((hyper 1) 2 3) 5)
(equal? ((hyper 2) 2 3) 6)
(equal? ((hyper 3) 2 3) 8)
(equal? ((hyper 4) 2 3) 16) ; 2 ^ (2 ^ 2)
(equal? ((hyper 4) 2 4) 65536)
(equal? ((hyper 5) 2 0) 1)
(equal? ((hyper 5) 2 1) 2)
(equal? ((hyper 5) 2 2) 4)
(equal? ((hyper 5) 2 3) 65536)