Move to use Aoc.Grid

bin/day2406.ml

@@ -1,50 +1,26 @@
-type map = { map : string; width : int; height : int }
-(** [map] represents a map with layout [map] and a [width] and [height].
-    [map.map] is a string of length [width * height] with the [i]th character
-    describing the position [(i mod map.width, i / map.width)]. *)
-
 (** [find_start strs] returns the location [(x, y)] of the starting position. *)
 let find_start map =
-  match String.index_from_opt map.map 0 '^' with
-  | Some i -> (i mod map.width, i / map.width)
+  match Aoc.Grid.idx_from_opt map 0 '^' with
+  | Some i -> Aoc.Grid.pos_of_idx map i
   | None -> failwith "find_start"
 
-(** [map_of_strings strs] returns the map generated from the input map described
-    by the list of strings [strs] *)
-let map_of_strings strs =
-  let width = String.length (List.hd strs) in
-  let map = List.fold_left String.cat "" strs in
-  let height = String.length map / width in
-  { map; width; height }
-
 (** [read_file fname] reads the input map from [fname]. It returns a
     [(map, pos, vel)] tuple, consisting of the obsticle map, initial position,
     and initial velocity. *)
 let read_file fname =
-  let lst = Aoc.strings_of_file fname in
-  let map = map_of_strings lst in
+  let map = Aoc.Grid.of_file fname in
   let pos = find_start map in
   (map, pos, (0, -1))
 
-(** [is_valid_pos map pos] returns true if the position [pos] is valid for the
-    map [map]. *)
-let is_valid_pos map (x, y) =
-  if y < 0 || y >= map.height then false
-  else if x < 0 || x >= map.width then false
-  else true
-
 (** [is_block map pos] returns [true] iff the location [pos] is a blockages in
     [map]. *)
-let is_block map (x, y) =
-  if is_valid_pos map (x, y) then map.map.[x + (y * map.width)] = '#' else false
+let is_block map pos =
+  if Aoc.Grid.pos_is_valid map pos then Aoc.Grid.get_by_pos map pos = '#'
+  else false
 
 (** [insert_block map pos] inserts a blockage at [pos] into [map] and returns
     the new map. *)
-let insert_block map (x, y) =
-  let idx = x + (y * map.width) in
-  let start = String.sub map.map 0 idx in
-  let e = String.sub map.map (idx + 1) (String.length map.map - idx - 1) in
-  { map with map = start ^ "#" ^ e }
+let insert_block map pos = Aoc.Grid.update_pos map pos '#'
 
 (** [move map (pos, vel)] moves [pos] one step forward on the [map]. [vel] gives
     the movement vector. If the movement will cause an obstacle to be hit then
@@ -60,7 +36,8 @@ let rec move map ((x, y), (dx, dy)) =
     off one of the sides. *)
 let walk_map map (pos, vel) =
   let rec impl acc (pos, vel) =
-    if is_valid_pos map pos then impl (pos :: acc) (move map (pos, vel))
+    if Aoc.Grid.pos_is_valid map pos then
+      impl (pos :: acc) (move map (pos, vel))
     else acc
   in
   impl [] (pos, vel)
@@ -75,7 +52,7 @@ let has_cycles map start =
   let rec impl agent1 ((pos', _) as agent2) =
     (* Only need to check pos' for validity because if pos is not valid then
        pos' must also be invalid, and have been invalid before this. *)
-    if not (is_valid_pos map pos') then false
+    if not (Aoc.Grid.pos_is_valid map pos') then false
     else if agent1 = agent2 then true
     else impl (move map agent1) (move map (move map agent2))
   in

bin/day2408.ml

@@ -1,29 +1,13 @@
-type map = { map : string; width : int; height : int }
-
-let map_of_file fname =
-  let strs = Aoc.strings_of_file fname in
-  let width = String.length (List.hd strs) in
-  let map = List.fold_left ( ^ ) "" strs in
-  let height = String.length map / width in
-  { map; width; height }
-
-let map_length map = String.length map.map
-let map_get_by_idx map idx = map.map.[idx]
-let map_pos_of_idx map idx = (idx mod map.width, idx / map.width)
-
-let map_is_valid_pos map (x, y) =
-  x >= 0 && x < map.width && y >= 0 && y < map.height
-
 module CharMap = Map.Make (Char)
 
 (** [get_station_indices map] returns a list of pairs mapping station ID to the
     indices in [map] where there is a station with that ID. *)
 let get_station_indices map =
   let rec impl acc idx =
-    if idx >= map_length map then acc
-    else if map_get_by_idx map idx = '.' then impl acc (idx + 1)
+    if idx >= Aoc.Grid.length map then acc
+    else if Aoc.Grid.get_by_idx map idx = '.' then impl acc (idx + 1)
     else
-      let station = map_get_by_idx map idx in
+      let station = Aoc.Grid.get_by_idx map idx in
       let update_fn lst =
         match lst with None -> Some [ idx ] | Some t -> Some (idx :: t)
       in
@@ -40,7 +24,7 @@ let get_antinodes1 acc _ (px, py) (px', py') =
 (** [add_antinodes lst map pos vel] adds antinodes at [pos + n * vel] to [lst]
     for all non-negative [n] that are valid positions in [map]. *)
 let rec add_antinodes lst map (x, y) (dx, dy) =
-  if map_is_valid_pos map (x, y) then
+  if Aoc.Grid.pos_is_valid map (x, y) then
     add_antinodes ((x, y) :: lst) map (x + dx, y + dy) (dx, dy)
   else lst
 
@@ -60,11 +44,11 @@ let process_stations map fn stations =
   let rec impl2 acc p t =
     match t with
     | [] -> acc
-    | h :: t -> impl2 (fn acc map p (map_pos_of_idx map h)) p t
+    | h :: t -> impl2 (fn acc map p (Aoc.Grid.pos_of_idx map h)) p t
   in
   let rec impl acc = function
     | [] -> acc
-    | h :: t -> impl (impl2 acc (map_pos_of_idx map h) t) t
+    | h :: t -> impl (impl2 acc (Aoc.Grid.pos_of_idx map h) t) t
   in
   List.map (impl []) stations
 
@@ -77,12 +61,12 @@ let part antifn map =
   |> List.map snd (* we do not care about the station IDs *)
   |> process_stations map antifn
   |> List.concat
-  |> List.filter (map_is_valid_pos map)
+  |> List.filter (Aoc.Grid.pos_is_valid map)
   |> List.sort_uniq Stdlib.compare
   |> List.length
 
 let _ =
-  Aoc.main map_of_file
+  Aoc.main Aoc.Grid.of_file
     [
       (string_of_int, part get_antinodes1); (string_of_int, part get_antinodes2);
     ]

bin/day2410.ml

@@ -1,33 +1,3 @@
-type grid = { grid : string; width : int; height : int }
-(** Type to hold the grid in... We should be moving this to the library soon *)
-
-(** [grid_of_file fname] loads a grid from the given file *)
-let grid_of_file fname =
-  let strs = Aoc.strings_of_file fname in
-  let grid = List.fold_left String.cat "" strs in
-  let width = String.length (List.hd strs) in
-  let height = String.length grid / width in
-  assert (width * height = String.length grid);
-  { grid; width; height }
-
-(** [grid_length grid] gives the length of the grid ([width * height]). *)
-let grid_length grid = String.length grid.grid
-
-(** [grid_get_by_idx grid idx] returns the element of [grid] at [idx]. *)
-let grid_get_by_idx grid idx = grid.grid.[idx]
-
-(** [grid_get_by_idx grid pos] returns the element of [grid] at [pos]. *)
-let grid_get_by_pos grid (x, y) = grid.grid.[x + (y * grid.width)]
-
-(** [grid_pos_if_idx grid idx] returns the [(x, y)] position of [idx] in [grid].
-*)
-let grid_pos_of_idx grid idx = (idx mod grid.width, idx / grid.width)
-
-(** [grid_pos_is_valid grid pos] returns [true] if and only if [pos] is a valid
-    position in [grid]. *)
-let grid_pos_is_valid grid (x, y) =
-  x >= 0 && y >= 0 && x < grid.width && y < grid.height
-
 (** [next_char ch] returns the next character after [ch]. *)
 let next_char ch = Char.chr (1 + Char.code ch)
 
@@ -42,10 +12,10 @@ let one = '1'
     '0'. The same endpoint may be returned multiple times if there are multiple
     routes to it. *)
 let find_trail grid pos0 =
-  assert (grid_get_by_pos grid pos0 = '0');
+  assert (Aoc.Grid.get_by_pos grid pos0 = '0');
   let add_pos lst pos digit =
-    if grid_pos_is_valid grid pos && grid_get_by_pos grid pos = digit then
-      pos :: lst
+    if Aoc.Grid.pos_is_valid grid pos && Aoc.Grid.get_by_pos grid pos = digit
+    then pos :: lst
     else lst
   in
   let add_poses lst (x, y) digit =
@@ -69,10 +39,10 @@ let find_trail grid pos0 =
     corresponds to the trails starting at index [n]. *)
 let find_trails grid =
   let rec impl acc idx =
-    if idx >= grid_length grid then acc
-    else if grid_get_by_idx grid idx <> '0' then impl acc (idx + 1)
+    if idx >= Aoc.Grid.length grid then acc
+    else if Aoc.Grid.get_by_idx grid idx <> '0' then impl acc (idx + 1)
     else (* grid_get_by_idx grid idx = 0 *)
-      impl (find_trail grid (grid_pos_of_idx grid idx) :: acc) (idx + 1)
+      impl (find_trail grid (Aoc.Grid.pos_of_idx grid idx) :: acc) (idx + 1)
   in
   impl [] 0 |> List.rev
 
@@ -83,7 +53,7 @@ let part sort_fn grid =
   |> List.fold_left ( + ) 0
 
 let _ =
-  Aoc.main grid_of_file
+  Aoc.main Aoc.Grid.of_file
     [
       (string_of_int, part (List.sort_uniq Stdlib.compare));
       (string_of_int, part Fun.id);

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

lib/aoc.mli

@@ -74,3 +74,50 @@ module IntPairSet : sig
   val add_seq : elt Seq.t -> t -> t
   val of_seq : elt Seq.t -> t
 end
+
+(** The [Grid] module is used to represent and manipulate a grid of characters.
+    Its main goals are to be non-mutable and have constant access times to
+    locations in the grid.
+
+    Grid locations can be accessed by index or (col, row) position. Indicies do
+    not guarantee an ordering on accesses - but iterating by index from 0 to
+    [Grid.length grid - 1] inclusive will cover the whole grid. *)
+module Grid : sig
+  type t
+  (** The type used to represent a grid *)
+
+  val of_file : string -> t
+  (** [Grid.of_file fname] returns a grid loaded from the file [fname] *)
+
+  val length : t -> int
+  (** [Grid.length grid] returns the length of the grid. *)
+
+  val get_by_idx : t -> int -> char
+  (** [Grid.get_by_idx grid idx] returns the character at index [idx] in [grid].
+  *)
+
+  val get_by_pos : t -> int * int -> char
+  (** [Grid.get_by_pos grid pos] returns the character at position [pos] in
+      [grid]. *)
+
+  val pos_of_idx : t -> int -> int * int
+  (** [Grid.pos_of_idx grid idx] returns the [(x, y)] position mapped by [idx]
+      in [grid]. *)
+
+  val idx_of_pos : t -> int * int -> int
+  (** [Grid.pos_of_idx grid pos] returns the index corresponding to [pos] in
+      [grid]. *)
+
+  val pos_is_valid : t -> int * int -> bool
+  (** [Grid.pos_is_valid grid pos] returns [true] if and only if [pos] is a
+      valid position in [grid]. *)
+
+  val idx_from_opt : t -> int -> char -> int option
+  (** [Grid.idx_from_opt grid start c] returns [Some idx] where [idx] is the
+      first location in [grid] at or after the [start] index which is [c]. It
+      returns [None] if [c] does not appear. *)
+
+  val update_pos : t -> int * int -> char -> t
+  (** [Grid.update_pos grid pos c] returns a grid with the character at position
+      [pos] changed to [c]. *)
+end