From 1a81d370510a01b482aae8033704d1a0523d11b7 Mon Sep 17 00:00:00 2001
From: Matias Linares <matias@deprecated.org>
Date: Thu, 5 Dec 2024 08:57:25 -0300
Subject: Add day 04 of 2024

---
 2024/aoc-utils.scm | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 47 insertions(+), 1 deletion(-)

(limited to '2024/aoc-utils.scm')

diff --git a/2024/aoc-utils.scm b/2024/aoc-utils.scm
index ed16bfd..9f22c47 100644
--- a/2024/aoc-utils.scm
+++ b/2024/aoc-utils.scm
@@ -1,12 +1,25 @@
 (define-module (aoc-utils)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-9)
+  #:use-module (srfi srfi-9 gnu)
   #:use-module (ice-9 regex)
   #:use-module (ice-9 rdelim)
   #:export (file->list
             file->str
             file->matrix
-            lines->number-list))
+            lines->number-list
+
+            <matrix>
+            matrix
+            make-matrix
+            matrix-inner
+            matrix-width
+            matrix-height
+            matrix-ref
+            matrix-valid-x?
+            matrix-valid-y?
+            matrix-valid-point?
+            list-flatten))
 
 (define (file->list filename)
   (let ((lines (string-split (call-with-input-file filename read-string) #\Newline)))
@@ -35,3 +48,36 @@
         ((< i 0))
       (set! retval (cons i retval)))
     retval))
+
+;; Matrix utilities
+
+(define-record-type <matrix>
+  (matrix inner width height)
+  matrix?
+  (inner matrix-inner)
+  (width matrix-width)
+  (height matrix-height))
+
+(define (make-matrix lst)
+  (let ((height (length lst))
+        (width (length (car lst))))
+    (matrix (list-flatten lst) width height)))
+
+(define (list-flatten lst)
+  (apply append lst))
+
+(define (matrix-ref matrix x y)
+  (if (matrix-valid-point? matrix x y)
+      (list-ref (matrix-inner matrix)
+                (+ x (* y (matrix-height matrix))))
+      #f))
+
+(define (matrix-valid-x? matrix x)
+  (and (>= x 0) (< x (matrix-width matrix))))
+
+(define (matrix-valid-y? matrix y)
+  (and (>= y 0) (< y (matrix-height matrix))))
+
+(define (matrix-valid-point? matrix x y)
+  (and (matrix-valid-x? matrix x)
+       (matrix-valid-y? matrix y)))
-- 
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