move vec2 into a new file & add a pretty printer

now it shows up properly in utop !!

.ocamlinit

@@ -0,0 +1 @@
+#install_printer Aoc.Vec2.pp;;

src/day8.ml

@@ -1,28 +1,8 @@
 open Containers
 
-module Vec2 : sig
-  type t
-
-  val directions : t list
-  val of_tuple : int * int -> t
-  val to_tuple : t -> int * int
-  val ( + ) : t -> t -> t
-  val at : 'a array array -> t -> 'a option
-end = struct
-  type t = int * int
-
-  let directions = [ 1, 0; 0, 1; -1, 0; 0, -1 ]
-  let of_tuple x = x
-  let to_tuple x = x
-  let ( + ) a b = Pair.map_same2 ( + ) a b
-
-  let at grid point =
-    let x, y = to_tuple point in
-    let open Option.Infix in
-    let* row = Array.get_safe grid y in
-    Array.get_safe row x
-  ;;
-end
+(* module Vec2 : sig *)
+(* end = struct *)
+(* end *)
 
 let parse_grid () =
   let lines = Utils.lines_of_input 8 in

src/dune

@@ -1,7 +1,7 @@
 (library
  (name aoc)
  (libraries re containers dune-site)
- (preprocess (pps ppx_regexp)))
+ (preprocess (pps ppx_regexp ppx_deriving.show)))
 
 (env
  (dev

src/vec2.ml

@@ -0,0 +1,21 @@
+open Containers
+
+type t = int * int [@@deriving show]
+
+let up = 0, 1
+let down = 0, -1
+let left = -1, 0
+let right = 1, 0
+let directions = [ up; down; left; right ]
+let of_tuple x = x
+let to_tuple x = x
+let ( + ) a b = Pair.map_same2 ( + ) a b
+let ( - ) a b = Pair.map_same2 ( - ) a b
+let ( = ) a b = Pair.equal ( = ) ( = ) a b
+
+let at grid point =
+  let x, y = to_tuple point in
+  let open Option.Infix in
+  let* row = Array.get_safe grid y in
+  Array.get_safe row x
+;;

src/vec2.mli

@@ -0,0 +1,13 @@
+type t [@@deriving show] [@@ocaml.toplevel_printer]
+
+val up : t
+val down : t
+val left : t
+val right : t
+val directions : t list
+val of_tuple : int * int -> t
+val to_tuple : t -> int * int
+val ( + ) : t -> t -> t
+val ( - ) : t -> t -> t
+val ( = ) : t -> t -> bool
+val at : 'a array array -> t -> 'a option