day 6 part 1 in scheme

scheme/advent-of-code.scm

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+;; Copyright (C) 2022
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+(define-module (advent-of-code)
+  #:export (read-file
+            read-file-lines
+            should-equal))
+
+(use-modules (ice-9 textual-ports))
+
+(define (read-file file)
+  (with-input-from-file file
+    (lambda ()      
+      (get-string-all (current-input-port)))
+    #:encoding "utf-8"))
+
+(define (read-file-lines file)
+  (string-split (read-file file) #\newline))
+
+(define (should-equal a b)
+  (unless (equal? a b)
+    (error (format #f "Expected ~A\nActual ~A\n" a b))))

scheme/day-6/input.txt

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+../../input/day-6.txt

scheme/day-6/solution.scm

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+#!/usr/bin/env -S guile -s
+!#
+
+;; Copyright (C) 2022
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+(use-modules (srfi srfi-1)
+             (ice-9 match)
+             (advent-of-code))
+
+(define (all-different? list)
+  (match list
+    (() '())
+    ((_) #t)
+    ((head . tail) (if (member head tail)
+                       #f
+                       (all-different? tail)))))
+
+(define (solution input marker-length)
+  (let loop ((position 0))
+    (let ((marker (take (drop input position) marker-length)))      
+      (if (all-different? marker)
+          (+ position marker-length)
+          (loop (+ position 1))))))
+
+(should-equal (all-different? '(a b c d)) #t)
+(should-equal (all-different? '(a a b c)) #f)
+(should-equal 7 (solution (string->list "mjqjpqmgbljsphdztnvjfqwrcgsmlb") 4))
+(should-equal 5 (solution (string->list "bvwbjplbgvbhsrlpgdmjqwftvncz") 4))
+(should-equal 6 (solution (string->list "nppdvjthqldpwncqszvftbrmjlhg") 4))
+(should-equal 10 (solution (string->list "nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg") 4))
+(should-equal 11 (solution (string->list "zcfzfwzzqfrljwzlrfnpqdbhtmscgvjw") 4))
+(should-equal 1794 (solution (string->list (read-file "input.txt")) 4))