day 2

day-2.scm

@@ -0,0 +1,41 @@
+(define (get-word text-port)
+  (let loop [(w '())]
+    (let [(c (get-char text-port))]
+      (if (or (eof-object? c) (char-whitespace? c))
+	(list->string (reverse w))
+	(loop (cons c w))))))
+
+(let [(file (open-input-file "day-2.input"))]
+  (let loop [(x 0) (y 0)]
+    (let [(amount (string->number (get-word file)))
+	  (move (get-word file))]
+      (cond
+	((string=? move "forward")
+	 (loop (+ x amount) y))
+	((string=? move "down")
+	 (loop x (+ y amount)))
+	((string=? move "up")
+	 (loop x (- y amount)))
+	(else
+	  (display "part 1: ")
+	  (display (* x y))
+	  (newline))))))
+
+(let [(file (open-input-file "day-2.input"))]
+  (let loop [(x 0) (y 0) (aim 0)]
+    (let [(amount (string->number (get-word file)))
+	  (move (get-word file))]
+      (cond
+	((string=? move "forward")
+	 (loop 
+	   (+ x amount) 
+	   (+ y (* aim amount))
+	   aim))
+	((string=? move "down")
+	 (loop x y (+ aim amount)))
+	((string=? move "up")
+	 (loop x y (- aim amount)))
+	(else
+	  (display "part 2: ")
+	  (display (* x y))
+	  (newline))))))