Interpreter for a polish notation "stack" language

Prefixed.rkt

#lang racket

(define eval   [lambda (p  ) (eval/s p '())])
(define eval/s [lambda (p s) (eval/k p s (lambda (x) x))])

(define eval/k
  [lambda (p s k)
    (cond {(eq? p '()) (k s)}
          {(number? (car p)) (eval/k (cdr p) s [lambda (s) (k (cons (car p) s))])}
          {(eq? (car p) 'dup) (eval/k (cdr p) s [lambda (s) (k (cons (car s) (cons (car s) (cdr s))))])}
          {(eq? (car p) 'swap) (eval/k (cdr p) s [lambda (s) (k (cons (cadr s) (cons (car s) (cddr s))))])}
          {else (cons 'err s)}
    )
  ]
)

(eval '())
(eval '(1))
(eval '(1 2))
(eval '(dup 1))
(eval '(dup 1 2))
(eval '(dup dup 1))
(eval '(dup dup 1 2))
(eval '(swap 1 2))
(eval '(dup swap 1 2))

Moved to https://github.com/dyokomizo/katren/blob/master/eval.rkt