restructure + lecutre 07

lectures/07/modules.ml

@@ -0,0 +1,47 @@
+(*
+  - a module can contain other modules as well as module type definitions
+  - a module type/sig (signature) can not contain modules but can contain other sigs
+  - for a .ml/.mli pair,
+    * anything not specified in .mli file is hidden
+    * everything specified in the .mli file must be defined in the .ml file
+*)
+
+module M = struct
+  let f x = 2 * x
+end;;
+
+module type S = module type of M;;
+
+module M = struct
+  let f x = 2 * x;;
+  let g x = 3 * x;;
+  module N = struct
+    type t = int
+  end
+end;;
+
+(* S signature is the same as M if loaded in utop *)
+module type S = module type of M;;
+
+(***** EXTENDED MODULES *****)
+
+(* lets extend List module *)
+module ListExt = struct
+  include List;; (* include module to extend *)
+  let to_array l = Array.of_list l;;
+end;;
+
+ListExt.to_array [3;2;7;6;8];;
+
+module F = Map.Make(String);;
+
+(* returns abstract type *)
+let m = F.empty |> F.add "hello" 1 |> F.add "hello" 2;;
+F.to_list m;;
+
+let incr key m =
+  F.update key (function | None -> Some 1 | Some x -> Some (x + 1))
+  m;;
+
+let m = incr "hello" m;;
+let m = incr "world" m;;