clean up day 2 solution with fancy stuff

2.rkt

@@ -1,24 +1,26 @@
-#lang racket
+#lang curly-fn racket
 
 (require "scripts/aoc.rkt")
 
 ;; solution for day 2
 
+;; checks if the count of the given character in the password is between lmin and lmax
 (define (password-valid-part1? lmin lmax char password)
-  (<= lmin (count (curry char=? char) (string->list password)) lmax))
+  (<= lmin (~>> password string->list (count #{char=? char %})) lmax))
 
+;; checks that exactly one of the positions specified by a and b contain char
 (define (password-valid-part2? a b char password)
-  (define pwd-chars (string->list password))
-  (xor (char=? (string-ref password (sub1 a)) char)
-       (char=? (string-ref password (sub1 b)) char)))
+  (define check #{char=? (string-ref password (sub1 %)) char})
+  (xor (check a) (check b)))
 
 (define (calculate valid-proc input)
   (for/sum ([line (in-list input)])
     (match line
-      [(pregexp #px"^([0-9]+)\\-([0-9]+) (.): (.*?)$" (list _ lmin lmax char password))
-       (if (valid-proc (string->number lmin) (string->number lmax)
-                       (string-ref char 0) password) 1 0)]
-      [_ (error "failed to parse" line)])))
+      [(pregexp #px"^([0-9]+)\\-([0-9]+) (.): (.*?)$"
+                (list _ (app string->number lmin) (app string->number lmax)
+                      (app #{string-ref % 0} char) password))
+       (if (valid-proc lmin lmax char password) 1 0)]
+      [_ (error "not shonks 🦈📉" line)])))
 
 (module+ main
   (define input (file->lines "inputs/2"))