commit d2acc5d04156c20564f7a69ecb395d930c192279
from: Lukas Henkel <lh@entf.net>
date: Mon Dec 16 07:06:16 2024 UTC

Simplify direction list cycling

commit - b80049b66156a9cbb8f881dc7a18b7c4a1642138
commit + d2acc5d04156c20564f7a69ecb395d930c192279
blob - 23476bde48d78b8972f836f9ccd30634a80af512
blob + a400cc67c3a5ca08ee2f743591aa96a47fa94351
--- src/day-16.lisp
+++ src/day-16.lisp
@@ -3,10 +3,10 @@
   (:export #:day-16))
 (in-package #:aoc/day-16)
 
-(defparameter *directions-clockwise* '((1 . 0) (0 . 1)
-                                       (-1 . 0) (0 . -1)))
-(defparameter *directions-counterclockwise* '((1 . 0) (0 . -1)
-                                              (-1 . 0) (0 . 1)))
+(defparameter *directions-clockwise* '(#1=(1 . 0) (0 . 1)
+                                       (-1 . 0) (0 . -1) #1#))
+(defparameter *directions-counterclockwise* '(#2=(1 . 0) (0 . -1)
+                                              (-1 . 0) (0 . 1) #2#))
 
 (defstruct node
   position
@@ -61,13 +61,11 @@
         when (char/= (map-cell map next) #\#)
           do (process-next open-list closed-list next current-dir (1+ current-cost) current)
         do (process-next open-list closed-list current-pos
-                         (or (cadr (member current-dir *directions-clockwise* :test #'equal))
-                             (first *directions-clockwise*))
+                         (cadr (member current-dir *directions-clockwise* :test #'equal))
                          (+ current-cost 1000)
                          current)
            (process-next open-list closed-list current-pos
-                         (or (cadr (member current-dir *directions-counterclockwise* :test #'equal))
-                             (first *directions-counterclockwise*))
+                         (cadr (member current-dir *directions-counterclockwise* :test #'equal))
                          (+ current-cost 1000)
                          current)))