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Merge pull request #3787 from luishendrix92/main
#21 - OCaml
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‎Roadmap/21 - CALLBACKS/ocaml/luishendrix92.ml

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open Printf
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(****************************************************************************)
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(* *)
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(* Callbacks (HoF) *)
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(* *)
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(* As a functional programming language, OCaml is perfectly capable of *)
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(* treating functions as first-class citizens; meaning, we can store them *)
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(* inside variables, accept them as parameters, return them from other *)
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(* functions, and more! *)
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(* *)
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(* In programming, a {b callback} is a function that is passed as an *)
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(* argument to a function, which will be later called (with or without *)
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(* arguments) once a certain task is completed synchronously or *)
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(* asynchronously. The term was popularized by the inception of NodeJS's *)
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(* single-threaded concurrent programming but it goes beyond just that... *)
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(* both in history and use cases. A callback can be just a function that *)
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(* represent a strategy, or can be a set of instructions to run at a *)
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(* certain point in time; it can be virtually any type of function, *)
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(* really; as long as it's passed as an argument to another function. *)
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(* *)
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(****************************************************************************)
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let with_named_parameters ~callback name =
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let greeting = sprintf "Hello, %s! How are you today?" name in
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printf "HoF 'with_named_parameters' will run callback with [%s]...\n" name;
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callback greeting;
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print_endline
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"Higher-Order Function 'with_named_parameters' finished execution!"
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;;
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let _ =
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(* Why have [callback] as a named parameter?
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It's idiomatic in the OCaml world... *)
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with_named_parameters
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~callback:(fun greeting -> printf "Greeting received: %s\n" greeting)
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"Luis";
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print_newline ()
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;;
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(**************************************************************************)
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(* *)
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(* Dificultad Extra (opcional) *)
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(* *)
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(* Crea un simulador de pedidos de un restaurante utilizando callbacks. *)
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(* Estará formado por una función que procesa pedidos. *)
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(* Debe aceptar el nombre del plato, una callback de confirmación, una *)
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(* de listo, y otra de entrega. *)
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(* *)
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(* - Debe imprimir una confirmación cuando empiece el procesamiento. *)
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(* - Debe simular un tiempo aleatorio entre 1 a 10 segundos entre *)
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(* procesos. *)
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(* - Debe invocar a cada callback siguiendo un orden de procesado. *)
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(* - Debe notificar que el plato está listo o ha sido entregado. *)
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(* *)
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(**************************************************************************)
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let wait_between_1_and_10_seconds () = Thread.delay (Random.float 9.0 +. 1.0)
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module Restaurant : sig
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val show_menu : unit -> unit
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val place_order
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: on_confirmed:(unit -> unit)
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-> on_ready:(unit -> unit)
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-> on_delivered:(string -> unit)
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-> int
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-> unit
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end = struct
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Random.self_init ()
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type dish =
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| HotDog
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| Cheeseburger
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| CaesarSalad
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| Chicken
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| Shortcake
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| Ramen
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[@@deriving show]
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let dish_of_int = function
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| 1 -> HotDog
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| 2 -> Cheeseburger
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| 3 -> CaesarSalad
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| 4 -> Chicken
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| 5 -> Shortcake
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| 6 -> Ramen
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| _ -> raise (Invalid_argument "Dish number not in the menu")
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;;
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let dish_to_emoji = function
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| HotDog -> "🌭"
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| Cheeseburger -> "🍔"
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| CaesarSalad -> "🥗"
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| Chicken -> "🍗"
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| Shortcake -> "🍰"
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| Ramen -> "🍜"
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;;
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let show_menu () =
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print_endline "#1 <- Hot dog";
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print_endline "#2 <- Cheeseburger";
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print_endline "#3 <- Caesar salad";
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print_endline "#4 <- Chicken wings";
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print_endline "#5 <- Strawberry shortcake";
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print_endline "#6 <- Ramen bowl"
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;;
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let process_order ~on_confirmed ~on_ready ~on_delivered dish =
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wait_between_1_and_10_seconds ();
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print_endline "Order was confirmed, invoking confirmation callback...";
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on_confirmed ();
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wait_between_1_and_10_seconds ();
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print_endline "Order is ready, invoking readiness callback...";
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on_ready ();
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wait_between_1_and_10_seconds ();
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print_endline "Order being delived to table, invoking delivery callback...";
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on_delivered (dish_to_emoji dish)
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;;
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let place_order ~on_confirmed ~on_ready ~on_delivered dish_number =
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let dish = dish_of_int dish_number in
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let order_thread =
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Thread.create (process_order ~on_confirmed ~on_ready ~on_delivered) dish
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in
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printf
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"Restaurant cashier says: Order [%s] has been placed!\n"
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(show_dish dish);
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print_endline "---------------------------------------------------";
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Thread.join order_thread
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;;
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end
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let _ =
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print_endline "Welcome to my restaurant! Here's the menu:";
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Restaurant.show_menu ();
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let dish_number =
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Moure.Io.prompt
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~err_msg:"Invalid number"
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~f:int_of_string
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"Choose a menu item between 1 and 6: "
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in
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match dish_number with
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| Ok dish_number ->
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Restaurant.place_order
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~on_confirmed:(fun () ->
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print_endline "Customer says: Time to take a seat :)")
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~on_ready:(fun () ->
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print_endline "Customer says: Food's ready? I'll be waiting!")
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~on_delivered:(fun emoji ->
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printf "Customer says: Yum, time to eat my [%s]!\n" emoji)
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dish_number
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| Error msg -> print_endline msg
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;;
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(* Output of [dune exec reto21]:
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HoF 'with_named_parameters' will run callback with [Luis]...
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Greeting received: Hello, Luis! How are you today?
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Higher-Order Function 'with_named_parameters' finished execution!
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Welcome to my restaurant! Here's the menu:
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#1 <- Hot dog
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#2 <- Cheeseburger
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#3 <- Caesar salad
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#4 <- Chicken wings
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#5 <- Strawberry shortcake
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#6 <- Ramen bowl
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Choose a menu item between 1 and 6: 2
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Restaurant cashier says: Order [Reto21.Restaurant.Cheeseburger] has been placed!
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---------------------------------------------------
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Order was confirmed, invoking confirmation callback...
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Customer says: Time to take a seat :)
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Order is ready, invoking readiness callback...
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Customer says: Food's ready? I'll be waiting!
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Order being delived to table, invoking delivery callback...
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Customer says: Yum, time to eat my [🍔]!
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*)

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