Advent 2021, day 2: simplify conditionals.

We have now learned about (when).

2021/day2/day2.rkt

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+#lang racket
+
+; part 1 vars
+(define h 0)
+(define d 0)
+; part 2 vars
+(define aim 0)
+(define h2 0)
+(define d2 0)
+
+(define v 0)
+(for ([t (in-lines)])
+	  (when (string-prefix? t "up")
+		 (set! v (string->number (string-trim t "up ")))
+		 (set! d (- d v))
+		 (set! aim (- aim v)))
+	  (when (string-prefix? t "down")
+		 (set! v (string->number (string-trim t "down ")))
+		 (set! d (+ d v))
+		 (set! aim (+ aim v)))
+	  (when (string-prefix? t "forward")
+		 (set! v (string->number (string-trim t "forward ")))
+		 (set! h (+ h v))
+		 (set! h2 (+ h2 v))
+		 (set! d2 (+ d2 (* aim v)))))
+
+(display (* h d))
+(display " ")
+(display (* h2 d2))

2021/day2/test1.txt

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+forward 5
+down 5
+forward 8
+up 3
+down 8
+forward 2