1 files changed, 150 insertions, 0 deletions
diff --git a/2025/ocaml/lib/domain/matrix.ml b/2025/ocaml/lib/domain/matrix.ml
new file mode 100644
index 0000000..bb703fc
--- /dev/null
+++ b/2025/ocaml/lib/domain/matrix.ml
@@ -0,0 +1,150 @@
+module M : sig
+  type 'a t = 'a array array
+
+  val empty : int -> int -> 'a -> 'a t
+  (** [empty rows columns initial] is an empty 2D array of size [rows] * [columns]
+      where each element in the array is initialized to [initial]. *)
+
+  val of_list : 'a list list -> 'a t
+  (** *)
+
+  val of_string : string -> string t
+  (** [of_string str] is a 2D array where every character is an element. *)
+
+  val get : 'a t -> int -> int -> 'a
+  (** [get matrix x y] is an alias for [matrix.(y).(x)] *)
+
+  val pp : ('a -> string) -> 'a t -> string
+  (** [pp matrix string_of_elt] is the string representation of the [matrix]
+      where [string_of_elt] is called on each element. *)
+end = struct
+  type 'a t = 'a array array
+
+  let empty cols rows initial = Array.make_matrix cols rows initial
+
+  let of_list lst = Array.of_list @@ List.map Array.of_list lst
+
+  let of_string str =
+    let lines =
+      str |> String.split_on_char '\n'
+      |> List.filter_map (fun line ->
+          let trimmed = String.trim line in
+          if trimmed <> "" then Some trimmed else None )
+    in
+    let char_lst =
+      List.map
+        (fun s -> s |> String.to_seq |> List.of_seq |> List.map Char.escaped)
+        lines
+    in
+    of_list char_lst
+
+  let get matrix x y = matrix.(y).(x)
+
+  let pp string_of_elt matrix =
+    Array.fold_left
+      (fun col_acc arr ->
+        let row =
+          Array.fold_left
+            (fun row_acc elt -> row_acc ^ string_of_elt elt)
+            "" arr
+        in
+        if col_acc = "" then row else col_acc ^ "\n" ^ row )
+      "" matrix
+end
+
+let%expect_test "matrix created from input is pretty-printed as the same matrix"
+    =
+  let example =
+    {|..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.|}
+  in
+  print_string @@ M.pp (fun s -> s) @@ M.of_string example ;
+  [%expect
+    {|..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.|}]
+
+let%expect_test "direct access of the matrix is in form matrix.(y).(x)" =
+  let example =
+    {|..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.|}
+  in
+  let matrix = M.of_string example in
+  print_string matrix.(0).(0) ;
+  [%expect "."] ;
+  print_string matrix.(0).(1) ;
+  [%expect "."] ;
+  print_string matrix.(0).(2) ;
+  [%expect "@"] ;
+  print_string matrix.(0).(3) ;
+  [%expect "@"] ;
+  print_string matrix.(0).(4) ;
+  [%expect "."] ;
+  print_string matrix.(0).(5) ;
+  [%expect "@"] ;
+  print_string matrix.(0).(6) ;
+  [%expect "@"] ;
+  print_string matrix.(0).(7) ;
+  [%expect "@"] ;
+  print_string matrix.(0).(8) ;
+  [%expect "@"] ;
+  print_string matrix.(0).(9) ;
+  [%expect "."]
+
+let%expect_test "[M.get matrix x y] is an alias for [matrix.(y).(x)]" =
+  let example =
+    {|..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.|}
+  in
+  let matrix = M.of_string example in
+  print_string @@ M.get matrix 0 0 ;
+  [%expect "."] ;
+  print_string @@ M.get matrix 1 0 ;
+  [%expect "."] ;
+  print_string @@ M.get matrix 2 0 ;
+  [%expect "@"] ;
+  print_string @@ M.get matrix 3 0 ;
+  [%expect "@"] ;
+  print_string @@ M.get matrix 4 0 ;
+  [%expect "."] ;
+  print_string @@ M.get matrix 5 0 ;
+  [%expect "@"] ;
+  print_string @@ M.get matrix 6 0 ;
+  [%expect "@"] ;
+  print_string @@ M.get matrix 7 0 ;
+  [%expect "@"] ;
+  print_string @@ M.get matrix 8 0 ;
+  [%expect "@"] ;
+  print_string @@ M.get matrix 9 0 ;
+  [%expect "."]