[racket] Rosetta Sokoban Solution

Hi Sean

2013/6/10 Sean Kanaley <skanaley at gmail.com>

> Also, for some reason Racket doesn't return values from mutations.  Why on earth (set! x 3) is void instead of 3 is a mystery, but it leads to things like:
>
> (define-match (x ...) (heap-min heap))
> (now-remove-it!)
>
> and, in addition to verbose naming:
>
> (vector-set! v i 4)
> v
>
> which should ideally be:
>
> (vec! v i 3)


Here is an alternative representation of levels using that allows you to
write (l p) to get the value of position p in level l. Also (l p x) sets the
character at position p in level l to x.

#lang racket
(struct level (h get/set)
  #:property prop:procedure (struct-field-index get/set))

(define (make-level strings)
  (define h (hash-copy
             (for*/hash ([(row i) (in-indexed strings)]
                         [(x j)   (in-indexed row)])
               (values (list i j) x))))
  (define (get p) (hash-ref h p))
  (define (set p x) (hash-set! h p x) x)
  (define get/set (case-lambda [(p) (get p)] [(p x) (set p x)]))
  (level h get/set))

(define l (make-level (list "########"
                            "#      #"
                            "#  . @ #"
                            "########")))

(l '(0 0))
(l '(0 0) #\.)
(l '(0 0))

 --
Jens Axel Søgaard