% LinkedList NYC Solution % silly, scheme, hack, brainfuck, #pinned % 2012-11-05
Though I hate competition1, I love ice cream, and so the [LinkedList’s programming contest] was a worth while endeavor.
I didn’t spend much time on it (I planned about 20 minutes since I had a already planned out what I was going to)–it ended up taking about 45 minutes. Phooey.
My play was simple. Create a program which writes a simple [brainfuck] program which is executed on a 6 instruction subset of brainfuck. If you ignore the looping construct, which is the only complicated part of a simple brainfuck system, then an interpreter is about 6 lines of code.
To add a few lines of code for my final trick, I enlisted the help of [Run Length Encoding]. The proverbial cherry on top, was formatting the code like a bowl of ice cream (I didn’t think to actually put a cherry on top–I probably would have won if I had).
(define (ntbf-eval x h d) (unless (null? x) (case (car x) ((#\>) (ntbf-eval (cdr x) h (+ d 1))) ((#\<) (ntbf-eval (cdr x) h (- d 1))) ((#\+) (begin (vector-set! h d (+ 1 (vector-ref h d))) (ntbf-eval (cdr x) h d))) ((#\-) (begin (vector-set! h d (- 1 (vector-ref h d))) (ntbf-eval (cdr x) h d))) ((#\.) (begin (format #t "~a" ( integer->char (vector-ref h d))) (ntbf-eval (cdr x) h d))) (else (error "invalid non turing brainfuck statement"))))) (define (prog-table) (let loop ((i 0) (accum '())) (if (< i 128) (loop (+ 1 i) (cons `(,(integer->char i) (,i #\+) (1 #\.)) accum)) accum))) (define (rld ps) (let ((char (cadr ps))) (let loop ((i (car ps)) (accum '())) (if (> i 0) (loop (- i 1) (cons char accum)) accum) ))) (define fragments (prog-table))(define (make-prog s) (let ((ls (string->list s))) (let loop ((ls ls) (accum '())) (if (not (null? ls)) (let ((p (assoc (car ls) fragments))) (if (not (null? p)) (loop (cdr ls) ( append accum (append (cdr p) '((1 #\>))))) (error "I only do ASCII"))) accum )))) (define (decode ls) (apply append (map rld ls))) (begin(ntbf-eval (decode (make-prog "LinkedList NYC")) (make-vector 100 0) 0) (newline)) ;; LinkedList Ice Cream Bowl ;; By Andrew Gwozdziweycz
The code runs in Guile 2.0+, or a sane scheme implementation that supports
BTW, some of the [other entries] were pretty cool. If only they’d use their time working on free software…
In fact, I’ve rated it [1 star] on [Combosaurus]. Why? Well, that’s a long story (I suppose), but it doesn’t bring out the best (in some ways, it does of course, but not the side I’d like to see) in people. ↩