A few more days
    
        | author | 
        Steve Losh <steve@stevelosh.com> | 
    
    
        | date | 
        Tue, 03 Dec 2019 20:15:07 -0500 | 
    
    
        | parents | 
        5b5c61ad8d2b  | 
    
    
        | children | 
        (none) | 
    
(defpackage :advent/2017/05 #.cl-user::*advent-use*)
(in-package :advent/2017/05)
(defun compute (data modification-function)
  (iterate
    (with maze = (fresh-vector data))
    (with bound = (1- (length maze)))
    (with address = 0)
    (while (<= 0 address bound))
    (counting t)
    (for offset = (aref maze address))
    (callf (aref maze address) modification-function)
    (incf address offset)))
(define-problem (2017 5) (data read-all) (342669 25136209)
  (values
    (compute data #'1+)
    (compute data (lambda (value) (+ value (if (>= value 3) -1 1))))))