implement sand dropping logic & pretty visuals

going down on the grid increases the int for y

src/day14.ml

@@ -5,12 +5,18 @@ type tile =
   | Rock
   | Sand
   | Start
+  | Path_D
+  | Path_L
+  | Path_R
 
 let char_of_tile = function
-  | Empty -> '.'
+  | Empty -> ' '
   | Rock -> '#'
   | Sand -> 'o'
   | Start -> 'v'
+  | Path_D -> '|'
+  | Path_L -> '/'
+  | Path_R -> '\\'
 ;;
 
 let parse_line line =
@@ -20,7 +26,18 @@ let parse_line line =
   Result.get_or_failwith @@ parse_string ~consume:All vec_list line
 ;;
 
-let parse_lines lines start =
+let draw_rocks grid points =
+  let open Grid in
+  let _ =
+    points
+    |> List.reduce (fun a b ->
+      iter_region grid a b (fun pos -> grid.%(pos) <- Rock);
+      b)
+  in
+  ()
+;;
+
+let parse_grid lines start =
   let points = List.map parse_line lines in
   let lx, hx, ly, hy =
     points
@@ -40,209 +57,258 @@ let parse_lines lines start =
   let width = hx - lx + (pad_x * 2) + 1 in
   let height = hy - ly + 1 in
   let start = Vec2.(start - extra) in
-  let points =
-    points
-    |> List.map (fun points -> points |> List.map (fun point -> Vec2.(point - extra)))
-  in
-  points, start, width, height
+  let open Grid in
+  let grid = init ~width ~height (fun _ -> Empty) in
+  grid.%(start) <- Start;
+  points
+  |> List.iter Fun.(List.map (fun point -> Vec2.(point - extra)) %> draw_rocks grid);
+  grid, start
 ;;
 
-let draw_rocks grid points =
+let rec drop_sand grid start draw_path =
+  let d = Vec2.(start + down) in
+  let l = Vec2.(d + left) in
+  let r = Vec2.(d + right) in
   let open Grid in
-  let _ =
-    points
-    |> List.reduce (fun a b ->
-      iter_region grid a b (fun pos -> grid.%(pos) <- Rock);
-      b)
-  in
-  ()
+  match grid.%(start), grid.%(l), grid.%(d), grid.%(r) with
+  | _, _, Some Empty, _ ->
+    if draw_path then grid.%(d) <- Path_D;
+    drop_sand grid d draw_path
+  | _, Some Empty, _, _ ->
+    if draw_path then grid.%(l) <- Path_L;
+    drop_sand grid l draw_path
+  | _, _, _, Some Empty ->
+    if draw_path then grid.%(r) <- Path_R;
+    drop_sand grid r draw_path
+  | _, _, None, _ -> Error ()
+  | Some Empty, _, _, _ ->
+    grid.%(start) <- Sand;
+    Ok ()
+  | _, _, _, _ -> failwith "pain"
+;;
+
+let rec drop_all_sand grid start =
+  match drop_sand grid start false with
+  | Ok () -> drop_all_sand grid start
+  | Error _ -> ()
+;;
+
+let%expect_test "Day 14 example" =
+  let lines = [ "498,4 -> 498,6 -> 496,6"; "503,4 -> 502,4 -> 502,9 -> 494,9" ] in
+  let start = Vec2.of_tuple (500, 0) in
+  let grid, start = parse_grid lines start in
+  let show_grid () = Printf.printf "%s" @@ Grid.draw grid char_of_tile in
+  show_grid ();
+  [%expect
+    {|
+          v
+
+
+
+        #   ##
+        #   #
+      ###   #
+            #
+            #
+    ######### |}];
+  drop_all_sand grid start;
+  let _ = drop_sand grid start true in
+  show_grid ();
+  [%expect
+    {|
+           v
+           |
+          /o
+         /ooo
+        /#ooo##
+       /o#ooo#
+      /###ooo#
+      |  oooo#
+     /o ooooo#
+    /######### |}]
 ;;
 
 let%expect_test "Day 14 example" =
-  (* let lines = [ "498,4 -> 498,6 -> 496,6"; "503,4 -> 502,4 -> 502,9 -> 494,9" ] in *)
   let lines = Utils.lines_of_input 14 in
   let start = Vec2.of_tuple (500, 0) in
-  let points, start, width, height = parse_lines lines start in
-  let grid = Grid.init ~width ~height (fun _ -> Empty) in
-  points |> List.iter @@ draw_rocks grid;
-  grid.Grid.%(start) <- Start;
-  Printf.printf "w %d h %d\n" width height;
+  let grid, start = parse_grid lines start in
+  drop_all_sand grid start;
+  let _ = drop_sand grid start true in
   Printf.printf "%s" @@ Grid.draw grid char_of_tile;
   [%expect
     {|
-    w 75 h 174
-    ..........v................................................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ........#..#...............................................................
-    ........#..#...............................................................
-    ..#######..######..........................................................
-    ..#.............#..........................................................
-    ..#.............#..........................................................
-    ..#.............#..........................................................
-    ..#.............#..........................................................
-    ..#.............#..........................................................
-    ..#.............#..........................................................
-    ..#.............#..........................................................
-    ..###############..........................................................
-    ...........................................................................
-    ...........................................................................
-    ..............######.......................................................
-    ...........................................................................
-    ...........######.######...................................................
-    ...........................................................................
-    ........######.######.######...............................................
-    ...........................................................................
-    .....######.######.######.######...........................................
-    ...........................................................................
-    ..######.######.######.######.######.......................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ....................................#.#....................................
-    ....................................#.#....................................
-    ..................................#.#.#....................................
-    ..................................#.#.#....................................
-    ................................#.#.#.#....................................
-    ................................#.#.#.#....................................
-    ................................#.#.#.#....................................
-    ................................#.#.#.#....................................
-    ................................#######....................................
-    ...........................................................................
-    ...........................................................................
-    .............................#.............................................
-    .............................#.............................................
-    .........................#...#.............................................
-    .........................#...#...#.#.......................................
-    .........................#...#...#.#.......................................
-    .........................#.#.#...#.#.......................................
-    .........................#.#.#.#.#.#.......................................
-    .........................#.#.#.#.#.#.......................................
-    .........................#.#.#.#.#.#.......................................
-    .........................#.#.#.#.#.#.......................................
-    .........................###########.......................................
-    ...........................................................................
-    ...........................................................................
-    .................................#....#....................................
-    .................................#....#....................................
-    .................................#....#....................................
-    .........................#########....##...................................
-    .........................#.............#...................................
-    .........................#.............#...................................
-    .........................#.............#...................................
-    .........................#.............#...................................
-    .........................###############...................................
-    ...........................................................................
-    ...........................................................................
-    ......................................#....................................
-    ..................................#...#....................................
-    ................................#.#...#....................................
-    ................................#.#...#...#................................
-    ................................#.#...#...#.#..............................
-    ................................#.#...#.#.#.#..............................
-    ................................#.#...#.#.#.#.#............................
-    ................................#.#.#.#.#.#.#.#............................
-    ................................#.#.#.#.#.#.#.#............................
-    ................................#.#.#.#.#.#.#.#............................
-    ................................###############............................
-    ...........................................................................
-    ...........................................................................
-    .........................................#.................................
-    .........................................#############.....................
-    ...........................................................................
-    ...........................................................................
-    ...................................................######..................
-    ...........................................................................
-    ...........................................................................
-    ................................................######.######..............
-    ...........................................................................
-    ...........................................................................
-    .............................................######.######.######..........
-    ...........................................................................
-    ...........................................................................
-    ..........................................######.######.######.######......
-    ...........................................................................
-    ...........................................................................
-    .......................................######.######.######.######.######..
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................#....#..........................
-    ...........................................######..........................
-    ...........................................................................
-    ...........................................................................
-    .......................................#.....#.............................
-    .......................................#.....#.............................
-    .......................................#.....#.............................
-    .......................................#.....#.............................
-    ....................................####.....#######.......................
-    ....................................#..............#.......................
-    ....................................#..............#.......................
-    ....................................#..............#.......................
-    ....................................#..............#.......................
-    ....................................#..............#.......................
-    ....................................################.......................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ..................................#...#....................................
-    ..................................#####....................................
-    ...........................................................................
-    ...........................................................................
-    ..............................#....#.......................................
-    ..............................#....#.......................................
-    ..............................#....#.......................................
-    .........................######....#########...............................
-    .........................#.................#...............................
-    .........................#.................#...............................
-    .........................#.................#...............................
-    .........................#.................#...............................
-    .........................###################...............................
-    ...........................................................................
-    ...........................................................................
-    ....................######.................................................
-    ...........................................................................
-    ...........................................................................
-    .......................######..............................................
-    ...........................................................................
-    ....................######.######..........................................
-    ...........................................................................
-    .................######.######.######......................................
-    ...........................................................................
-    ...........................................................................
-    ...........................................................................
-    ...........#...............................................................
-    ...........#...............................................................
-    ...........#.....#.........................................................
-    ...........#...#.#.#.......................................................
-    ...........#...#.#.#.......................................................
-    ...........#.#.#.#.#.......................................................
-    ...........#.#.#.#.#.......................................................
-    ...........#.#.#.#.#.......................................................
-    ...........#.#.#.#.#.......................................................
-    ...........#########.......................................................
-    ...........................................................................
-    ...........................................................................
-    .................######....................................................
-    ...........................................................................
-    ...........................................................................
-    ..............######.######................................................
-    ...........................................................................
-    ...........................................................................
-    ...........######.######.######............................................
-    ...........................................................................
-    ...........................................................................
-    ........######.######.######.######........................................ |}]
+            v
+            |
+            |
+            |
+            |
+            |
+            |
+            |
+            |
+           oo\
+          oooo\
+         oooooo\
+        oooooooo\
+       ooo#oo#ooo\
+      oooo#oo#oooo\
+    #######oo######\
+    #     oooo    #o\
+    #    oooooo   #oo\
+    #   oooooooo  #ooo\
+    #  oooooooooo #oooo\
+    # oooooooooooo#ooooo\
+    #ooooooooooooo#oooooo\
+    #ooooooooooooo#ooooooo\
+    ###############oooooooo\
+                  oooooooooo\
+                 oooooooooooo\
+                ######oooooooo\
+                     oooooooooo\
+             ###### ######oooooo\
+                         oooooooo\
+          ###### ###### ######oooo\
+                             oooooo\
+       ###### ###### ###### ######oo\
+                                 oooo\
+    ###### ###### ###### ###### ######\
+                                      |
+                                      |
+                                      |
+                                      |
+                                     /# #
+                                    /o# #
+                                   /#o# #
+                                  /o#o# #
+                                 /#o#o# #
+                                 |#o#o# #
+                                 |#o#o# #
+                                 |#o#o# #
+                                 |#######
+                                 |
+                                oo\
+                               #ooo\
+                               #oooo\
+                           #   #ooooo\
+                           #   #ooo#o#\
+                           #   #ooo#o#|
+                           # # #ooo#o#|
+                           # # #o#o#o#|
+                           # # #o#o#o#|
+                           # # #o#o#o#|
+                           # # #o#o#o#|
+                           ###########|
+                                     oo\
+                                    oooo\
+                                   #oooo#\
+                                   #oooo#|
+                                   #oooo#|
+                           #########oooo##\
+                           #       oooooo#|
+                           #      ooooooo#|
+                           #     oooooooo#|
+                           #    ooooooooo#|
+                           ###############|
+                                          |
+                                          |
+                                        #oo\
+                                    #   #ooo\
+                                  # #   #oooo\
+                                  # #   #ooo#o\
+                                  # #   #ooo#o#\
+                                  # #   #o#o#o#o\
+                                  # #   #o#o#o#o#\
+                                  # # # #o#o#o#o#|
+                                  # # # #o#o#o#o#o\
+                                  # # # #o#o#o#o#oo\
+                                  ###############ooo\
+                                                ooooo\
+                                               ooooooo\
+                                           #  ooooooooo\
+                                           #############\
+                                                       oo\
+                                                      oooo\
+                                                     ######\
+                                                          /o
+                                                         /ooo
+                                                  ######/######
+                                                       /o
+                                                      /ooo
+                                               ######/###### ######
+                                                    /o
+                                                   /ooo
+                                            ######/###### ###### ######
+                                                 /o
+                                                /ooo
+                                         ######/###### ###### ###### ######
+                                               |
+                                               |
+                                              /o
+                                             /ooo
+                                            /#oooo#
+                                           /o######
+                                          /ooo
+                                         /ooooo
+                                        /#ooooo#
+                                        |#ooooo#
+                                       /o#ooooo#
+                                      /oo#ooooo#
+                                     /####ooooo#######
+                                     |#  ooooooo     #
+                                     |# ooooooooo    #
+                                     |#ooooooooooo   #
+                                     |#oooooooooooo  #
+                                     |#ooooooooooooo #
+                                     |################
+                                    /o
+                                   /ooo
+                                  /ooooo
+                                 /oo#ooo#
+                                /ooo#####
+                               /ooooo
+                              /ooooooo
+                             /oo#oooo#o
+                            /ooo#oooo#oo
+                           /oooo#oooo#ooo
+                          /######oooo#########
+                          |#    oooooo       #
+                          |#   oooooooo      #
+                          |#  oooooooooo     #
+                         /o# oooooooooooo    #
+                        /oo###################
+                       /oooo
+                      /oooooo
+                     /######oo
+                     |     oooo
+                     |    oooooo
+                     |   ######oo
+                     |        oooo
+                    /o###### ######
+                   /ooo
+                  /###### ###### ######
+                  |
+                  |
+                  |
+             #   oo\
+             #  oooo\
+             # oooo#o\
+             #ooo#o#o#\
+             #ooo#o#o#|
+             #o#o#o#o#|
+             #o#o#o#o#|
+             #o#o#o#o#|
+             #o#o#o#o#|
+             #########|
+                     oo\
+                    oooo\
+                   ######\
+                        /o
+                       /ooo
+                ######/######
+                     /o
+                    /ooo
+             ######/###### ######
+                  /o
+                 /ooo
+          ######/###### ###### ###### |}]
 ;;

src/day9.ml

@@ -24,7 +24,7 @@ let next_pos head tail =
   then tail
   else (
     let x_dir = if dx > 0 then Vec2.right else Vec2.left in
-    let y_dir = if dy > 0 then Vec2.up else Vec2.down in
+    let y_dir = if dy > 0 then Vec2.down else Vec2.up in
     let dir =
       if abs dx = abs dy
       then Vec2.(x_dir + y_dir)

src/grid.ml

@@ -36,7 +36,7 @@ let set_e grid point item =
   else failwith "point out of bounds!"
 ;;
 
-let ( .%() ) = at_e
+let ( .%() ) = at
 let ( .%()<- ) = set_e
 
 let find (grid : 'a t) pred =
@@ -88,7 +88,7 @@ let draw grid printer =
   let str = ref [] in
   iter grid (fun point ->
     let item = grid.%(point) in
-    let char = printer item 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

src/grid.mli

@@ -3,7 +3,7 @@ type 'a t [@@deriving show]
 val at : 'a t -> Vec2.t -> 'a option
 val at_e : 'a t -> Vec2.t -> 'a
 val set_e : 'a t -> Vec2.t -> 'a -> unit
-val ( .%() ) : 'a t -> Vec2.t -> 'a
+val ( .%() ) : 'a t -> Vec2.t -> 'a option
 val ( .%()<- ) : 'a t -> Vec2.t -> 'a -> unit
 val init : width:int -> height:int -> (Vec2.t -> 'a) -> 'a t
 val of_lines : (char -> 'a) -> string list -> 'a t

src/vec2.ml

@@ -7,10 +7,10 @@ type t =
 [@@deriving show]
 
 let origin = { x = 0; y = 0 }
-let up = { x = 0; y = 1 }
-let down = { x = 0; y = -1 }
-let left = { x = -1; y = 0 }
+let up = { x = 0; y = -1 }
+let down = { x = 0; y = 1 }
 let right = { x = 1; y = 0 }
+let left = { x = -1; y = 0 }
 let directions = [ up; down; left; right ]
 let of_tuple (x, y) = { x; y }
 let to_tuple { x; y } = x, y