refactor day 14 a bit

src/day14.ml

@@ -10,7 +10,7 @@ type tile =
   | Path_R
 
 let char_of_tile = function
-  | Empty -> '_'
+  | Empty -> '-'
   | Rock -> '#'
   | Sand -> 'o'
   | Start -> 'v'
@@ -73,26 +73,32 @@ let parse_grid lines start =
   grid, start
 ;;
 
+type is_done =
+  | Continue
+  | Done
+
 let rec drop_sand_abyss draw_path grid start =
   let d = Vec2.(start + down) in
   let l = Vec2.(d + left) in
   let r = Vec2.(d + right) in
   let open Grid in
-  match grid.%(start), grid.%(l), grid.%(d), grid.%(r) with
-  | _, _, Some Empty, _ ->
+  match grid.%(l), grid.%(d), grid.%(r) with
+  | _, None, _ -> Done
+  | _, Some Empty, _ ->
     if draw_path then grid.%(d) <- Path_D;
     drop_sand_abyss draw_path grid d
-  | _, Some Empty, _, _ ->
+  | Some Empty, _, _ ->
     if draw_path then grid.%(l) <- Path_L;
     drop_sand_abyss draw_path grid l
-  | _, _, _, Some Empty ->
+  | _, _, Some Empty ->
     if draw_path then grid.%(r) <- Path_R;
     drop_sand_abyss draw_path grid r
-  | _, _, None, _ -> Error ()
-  | Some Empty, _, _, _ ->
-    grid.%(start) <- Sand;
-    Ok ()
-  | _, _, _, _ -> failwith "oh no!"
+  | _, _, _ ->
+    (match grid.%(start) with
+     | Some Empty ->
+       grid.%(start) <- Sand;
+       Continue
+     | _ -> failwith "oh no!")
 ;;
 
 let rec drop_sand_floor grid start =
@@ -100,23 +106,25 @@ let rec drop_sand_floor grid start =
   let l = Vec2.(d + left) in
   let r = Vec2.(d + right) in
   let open Grid in
-  match grid.%(start), grid.%(l), grid.%(d), grid.%(r) with
-  | _, _, Some Empty, _ -> drop_sand_floor grid d
-  | _, Some Empty, _, _ -> drop_sand_floor grid l
-  | _, _, _, Some Empty -> drop_sand_floor grid r
-  | Some Empty, _, _, _ ->
-    grid.%(start) <- Sand;
-    Ok ()
-  | Some Start, _, _, _ ->
-    grid.%(start) <- Sand;
-    Error ()
-  | _, _, _, _ -> failwith "ooooo!"
+  match grid.%(l), grid.%(d), grid.%(r) with
+  | _, Some Empty, _ -> drop_sand_floor grid d
+  | Some Empty, _, _ -> drop_sand_floor grid l
+  | _, _, Some Empty -> drop_sand_floor grid r
+  | _, _, _ ->
+    (match grid.%(start) with
+     | Some Empty ->
+       grid.%(start) <- Sand;
+       Continue
+     | Some Start ->
+       grid.%(start) <- Sand;
+       Done
+     | _ -> failwith "oh no!")
 ;;
 
 let rec drop_all_sand drop grid start =
   match drop grid start with
-  | Ok () -> drop_all_sand drop grid start
-  | Error _ -> ()
+  | Continue -> drop_all_sand drop grid start
+  | Done -> ()
 ;;
 
 let%expect_test "Day 14.1 example" =
@@ -130,17 +138,17 @@ let%expect_test "Day 14.1 example" =
   [%expect
     {|
     24 grains
-    _____________v_____________
-    _____________|_____________
-    ____________/o_____________
-    ___________/ooo____________
-    __________/#ooo##__________
-    _________/o#ooo#___________
-    ________/###ooo#___________
-    ________|__oooo#___________
-    _______/o_ooooo#___________
-    ______/#########___________
-    ______|____________________ |}]
+    -------------v-------------
+    -------------|-------------
+    ------------/o-------------
+    -----------/ooo------------
+    ----------/#ooo##----------
+    ---------/o#ooo#-----------
+    --------/###ooo#-----------
+    --------|--oooo#-----------
+    -------/o-ooooo#-----------
+    ------/#########-----------
+    ------|-------------------- |}]
 ;;
 
 let%expect_test "Day 14.2 example" =
@@ -153,17 +161,17 @@ let%expect_test "Day 14.2 example" =
   [%expect
     {|
     93 grains
-    _____________o_____________
-    ____________ooo____________
-    ___________ooooo___________
-    __________ooooooo__________
-    _________oo#ooo##o_________
-    ________ooo#ooo#ooo________
-    _______oo###ooo#oooo_______
-    ______oooo_oooo#ooooo______
-    _____oooooooooo#oooooo_____
-    ____ooo#########ooooooo____
-    ___ooooo_______ooooooooo___ |}]
+    -------------o-------------
+    ------------ooo------------
+    -----------ooooo-----------
+    ----------ooooooo----------
+    ---------oo#ooo##o---------
+    --------ooo#ooo#ooo--------
+    -------oo###ooo#oooo-------
+    ------oooo-oooo#ooooo------
+    -----oooooooooo#oooooo-----
+    ----ooo#########ooooooo----
+    ---ooooo-------ooooooooo--- |}]
 ;;
 
 let%expect_test "Day 14.1" =