make Grid.draw more flexible

- printer callback includes Vec2.t in the arguments now
- added optional rev_x and rev_y params

src/day14.ml

@@ -9,7 +9,7 @@ type tile =
   | Path_L
   | Path_R
 
-let char_of_tile = function
+let char_of_tile _ = function
   | Empty -> '-'
   | Rock -> '#'
   | Sand -> 'o'

src/grid.ml

@@ -82,12 +82,16 @@ let iter grid callback =
   iter_region grid a b callback
 ;;
 
-let draw grid printer =
-  let str = ref [] in
+let draw grid ?(rev_y = false) ?(rev_x = false) printer =
+  let line = ref [] in
+  let lines = ref [] in
   iter grid (fun point ->
     let item = grid.%(point) in
-    let char = printer @@ Option.get_exn_or "iter is broken" item in
-    str := !str @ [ char ];
-    if point.x = grid.width - 1 then str := !str @ [ '\n' ]);
-  String.of_list !str
+    let char = printer point (Option.get_exn_or "iter is broken" item) in
+    line := if rev_x then char :: !line else !line @ [ char ];
+    if List.length !line = grid.width
+    then (
+      lines := !lines @ [ String.of_list !line ];
+      line := []));
+  String.concat "\n" (if rev_y then List.rev !lines else !lines)
 ;;

src/grid.mli

@@ -11,4 +11,4 @@ val find : 'a t -> ('a -> bool) -> (Vec2.t * 'a) option
 val count : 'a t -> ('a -> bool) -> int
 val iter_region : 'a t -> Vec2.t -> Vec2.t -> (Vec2.t -> unit) -> unit
 val iter : 'a t -> (Vec2.t -> unit) -> unit
-val draw : 'a t -> ('a -> char) -> string
+val draw : 'a t -> ?rev_y:bool -> ?rev_x:bool -> (Vec2.t -> 'a -> char) -> string