Belated 2024 first puzzle solution

2024/puzzle-1.lisp

@@ -0,0 +1,15 @@
+(load "util.lisp")
+
+(--> (uiop:read-file-lines "1-input")
+     (loop for line in _
+           for x = (search "   " line)
+           collect (parse-integer (subseq line 0 x)) into left
+           collect (parse-integer (subseq line (+ x 3))) into right
+           finally (return (list (sort left #'<) (sort right #'<))))
+     (format t "Round 1: ~a~%Round 2: ~a~%"
+             (loop for x in (car _)
+                   for y in (cadr _)
+                   sum (abs (- y x)))
+             (loop for item in (car _)
+                   for count = (count item (cadr _))
+                   sum (* item count))))

2024/util.lisp

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+(defmacro --> (first &rest functions)
+  (if (null functions)
+      first
+      `(let* ,(loop :for f :in (cons first functions)
+                    appending `((_ ,f)))
+         _)))
+
+(defun zip (a b)
+  (loop for i in a
+        for j in b
+        collect (cons i j)))