Moved Grid to Aoc module.

lib/aoc.ml

@@ -21,7 +21,10 @@ let main prep parts =
         Printf.printf "Usage: %s <fname>\n" Sys.executable_name;
         exit 2
   with e ->
-    Printf.printf "An error occured: %s\n" (Printexc.to_string e);
+    Printf.fprintf stderr "An error occured: %s\n" (Printexc.to_string e);
+    if Printexc.backtrace_status () then (
+      Printf.fprintf stderr "Backtrace:\n";
+      Printexc.print_backtrace stderr);
     exit 1
 
 module IntPair = struct
@@ -32,3 +35,34 @@ module IntPair = struct
 end
 
 module IntPairSet = Set.Make (IntPair)
+
+module Grid = struct
+  type t = { grid : string; width : int; height : int }
+
+  let of_file fname =
+    let strs = strings_of_file fname in
+    let width = String.length (List.hd strs) in
+    let grid = List.fold_left ( ^ ) "" strs in
+    let height = String.length grid / width in
+    { grid; width; height }
+
+  let length grid = String.length grid.grid
+  let pos_of_idx grid idx = (idx mod grid.width, idx / grid.width)
+  let idx_of_pos grid (x, y) = x + (y * grid.width)
+  let get_by_idx grid idx = grid.grid.[idx]
+  let get_by_pos grid pos = get_by_idx grid (idx_of_pos grid pos)
+
+  let pos_is_valid grid (x, y) =
+    x >= 0 && x < grid.width && y >= 0 && y < grid.height
+
+  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 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 }
+end