Day 2024 part 1

lib/aoc.ml

@@ -66,14 +66,15 @@ module Grid = struct
 
   let idx_from_opt grid = String.index_from_opt grid.grid
 
-  let update_pos grid pos c =
-    let idx = idx_of_pos grid pos in
+  let update_idx grid idx c =
     let builder = Buffer.create (length grid) in
     Buffer.add_string builder (String.sub grid.grid 0 idx);
     Buffer.add_char builder c;
     Buffer.add_string builder
       (String.sub grid.grid (idx + 1) (length grid - idx - 1));
     { grid with grid = Buffer.contents builder }
+
+  let update_pos grid pos c = update_idx grid (idx_of_pos grid pos) c
 end
 
 let log10i i =

lib/aoc.mli

@@ -143,4 +143,8 @@ module Grid : sig
   val update_pos : t -> int * int -> char -> t
   (** [Grid.update_pos grid pos c] returns a grid with the character at position
       [pos] changed to [c]. *)
+
+  val update_idx : t -> int -> char -> t
+  (** [Grid.update_pos grid idx c] returns a grid with the character at index
+      [idx] changed to [c]. *)
 end