2.rkt

#lang racket
(require threading)



(define (parse-line line)
  (match (string-split line " ")
    [(list dir amnt)
     (cons (parse-dir dir) (parse-amnt amnt))]))

(define (parse-dir dir)
  (cond
    [(string=? "forward" dir) forward!]
    [(string=? "down" dir) down!]
    [(string=? "up" dir) up!]))

(define (parse-amnt amnt)
  (string->number amnt))

(define position 0)
(define depth 0)
(define aim 0)

(define (forward! n)
  (set! position (+ position n))
  (set! depth (+ depth (* aim n))))

(define (up! n)
  (set! aim (- aim n)))

(define (down! n)
  (set! aim (+ aim n)))


(define src
  (~> 
   (with-input-from-file
       "/tmp/input"
     (λ () (port->lines (current-input-port))))
   (map parse-line _)))



(for [(op (in-list src))]
  ((car op) (cdr op)))

(displayln (format "Position: ~a" position))
(displayln (format "Depth: ~a" depth))
(displayln (format "Result: ~a" (* depth position)))