not working

2016
Matthew Butterick 8 years ago
parent e050f6b654
commit 72cfb19724

@ -3,33 +3,59 @@
(module+ reader (module+ reader
(provide read-syntax) (provide read-syntax)
(define (read-syntax path port) (define (read-syntax path port)
(define turn-strings (string-split (port->string port) ", "))
(define turn-pattern #px"^([LR])(\\d+)$")
(define turn-datums
(for*/list ([tstr (in-list turn-strings)])
(define match-result (regexp-match turn-pattern (string-trim tstr)))
`(turn ,@(cdr (or match-result empty)))))
(strip-bindings (strip-bindings
#`(module day01-mod "day01.rkt" #`(module day01-mod "day01.rkt"
#,@(for/list ([t (in-list (string-split (port->string port) ", "))]) #,@turn-datums))))
`(turn ,@(string-split (string-trim t) #px"(?<=[LR])")))))))
(define-macro (mb . TURNS) (define-macro (mb . TURNS)
#'(#%module-begin #'(#%module-begin
(solve . TURNS))) (solve . TURNS)))
(provide (rename-out [mb #%module-begin])) (provide (rename-out [mb #%module-begin]))
(define (solve . turns) (define (loc-dist loc)
(define loc
(let loop ([loc 0]
[dir 1]
[turns turns])
(if (empty? turns)
loc
(let* ([turn (car turns)]
[rotation (car turn)]
[dist (cdr turn)]
[new-dir (* dir rotation)])
(loop (+ loc (* new-dir dist)) new-dir (cdr turns))))))
(+ (abs (imag-part loc)) (abs (real-part loc)))) (+ (abs (imag-part loc)) (abs (real-part loc))))
(define-macro (turn DIR DIST) (define (locs-between loca locb)
(with-pattern ([NEW-DIR (syntax-case #'DIR () (range loca (add1 locb)))
["L" #'+i]
["R" #'-i])]) (module+ test
#'(cons NEW-DIR (string->number DIST)))) (require rackunit)
(check-equal? (locs-between 0 3) '(0 1 2 3))
(check-equal? (locs-between 3 0) (reverse (locs-between 0 3)))
(check-equal? (locs-between +0i +3i) '(+0i +1i +2i +3i))
(check-equal? (locs-between +3i +0i) (reverse (locs-between +0i +3i))))
(define (solve . turns)
(define first-loc-visited-twice #f)
(define north 0+1i)
(let loop ([locs (list 0+0i)] [dir north] [turns turns])
(if (empty? turns)
(displayln (format "part 1 (dist of final location): ~a" (loc-dist (car locs))))
(let* ([turn (car turns)]
[rotation (car turn)]
[new-dir (* dir rotation)]
[dist (cdr turn)]
[loc (car locs)]
[new-loc (+ loc (* new-dir dist))])
(when (and
(not first-loc-visited-twice)
(report* locs loc new-loc (member new-loc locs)))
(set! first-loc-visited-twice new-loc)
(displayln (format "part 2 (dist of first twice-visited location): ~a" (loc-dist new-loc))))
(loop (report (append (locs-between new-loc loc) (cdr locs))) new-dir (cdr turns))))))
(define-macro-cases turn
[(_ DIR DIST)
(with-pattern ([NEW-DIR (syntax-case #'DIR ()
["L" #'+i]
["R" #'-i])])
#'(cons NEW-DIR (string->number DIST)))]
[else #'(void)])
(provide turn) (provide turn)