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Merge pull request #4930 from luishendrix92/main
#29 - OCaml
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‎Roadmap/29 - SOLID ISP/ocaml/luishendrix92.ml

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(******************************************************************************)
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(* *)
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(* Interface Segregation Principle *)
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(* *)
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(* The core concept of this principle (the 'I' in {b SOLID}) is, a class *)
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(* should not be forced to implement methods that it doesn't need, caused *)
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(* by the implementation of a broad interface, or inheriting from a general *)
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(* abstract class that covers more ground than it should. *)
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(* *)
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(* The proposed solution is to create smaller interfaces that are only im- *)
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(* plemented if the class needs those methods and/or members and only *)
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(* inherit from a base class that won't force unwanted implementations. It *)
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(* goes hand in hand with the Liskov-Substitution Principle as it helps *)
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(* reduce the amount of exceptions thrown. *)
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(* *)
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(******************************************************************************)
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open Printf
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(* This interface violates the ISP because if implemented by a specific type of
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coffee machine, it will be forced to implement methods that it doesn't need
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and thus it'll need to either throw an exception or provide a NoOP body. *)
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class type coffee_machine_violating_isp = object
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method drip_brew : unit
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method replace_filter : unit
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method steam_milk : unit
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method pressure_brew : unit
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method add_ground_coffee : unit
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end
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class type coffee_machine = object
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method brew : unit
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method add_ground_coffee : unit
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end
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class type drip = object
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(* Inheriting a class type from another class type in OCaml is the same
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as extending an interface in OOP languages. Though we can't implement
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multiple interfaces, we can in fact inherit from multiple classes! *)
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inherit coffee_machine
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method drip_brew : unit
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method replace_filter : unit
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end
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class type espresso = object
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inherit coffee_machine
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method steam_milk : unit
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method pressure_brew : unit
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end
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class drip_machine : drip =
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object (self)
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method private drip_brew = print_endline "Brewing through a paper filter..."
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method add_ground_coffee =
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print_endline "Adding ground coffee to drip coffee machine..."
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method replace_filter = print_endline "Replacing paper filter..."
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method brew = self#drip_brew
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end
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class espresso_machine : espresso =
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object (self)
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method private pressure_brew =
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print_endline "Brewing through an espresso portafilter..."
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method add_ground_coffee =
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print_endline
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"Adding and compressing ground coffee to espresso machine..."
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method steam_milk = print_endline "Steaming milk for latte art..."
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method brew = self#pressure_brew
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end
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let _ =
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let oster_drip : drip_machine = new drip_machine in
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let barista : espresso_machine = new espresso_machine in
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oster_drip#add_ground_coffee;
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oster_drip#brew;
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oster_drip#replace_filter;
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barista#add_ground_coffee;
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barista#brew;
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barista#steam_milk
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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 gestor de impresoras. *)
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(* Requisitos: *)
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(* 1. Algunas impresoras solo imprimen en blanco y negro. *)
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(* 2. Otras solo a color. *)
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(* 3. Otras son multifunción, pueden imprimir, escanear y enviar fax. *)
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(* Instrucciones: *)
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(* 1. Implementan el sistema, con los diferentes tipos de impresoras y fun- *)
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(* ciones. *)
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(* 2. Aplica el ISP a la implementación. *)
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(* 3. Desarrolla un código que compruebe que se cumple el principio. *)
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(* *)
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(******************************************************************************)
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class virtual black_white_printing =
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object
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method virtual print_b_and_w : string -> unit
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end
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class virtual color_printing =
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object
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method virtual print_color : string -> unit
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end
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class virtual fax (number : string) =
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object
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val phone_number = number
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method virtual send_document : string -> string -> unit
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end
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class virtual scanner =
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object
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method virtual scan_document : string -> unit
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end
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class bw_printer =
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object
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inherit black_white_printing
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method print_b_and_w docfile =
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printf "Printing [%s] in black and white...\n" docfile
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end
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class color_printer =
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object
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inherit color_printing
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method print_color docfile =
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printf "Printing [%s] in CYMK color...\n" docfile
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end
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class multifunctional_printer (number : string) =
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object (self)
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(* As I mentioned before, OCaml's class system offers multiple inheritance
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but I could have also made them interfaces (class types) and in order to
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create an interface that 'implements' all of them we could have done:
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{[
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class multifunctional_printer (number : string) : object
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inherit color_printing
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inherit black_white_printing
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inherit scanner
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inherit fax
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end = object (self) end
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]}
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This way we'd be forced to implement all of those methods but with one
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catch: using class types 'seals' a class, meaning we can't expose more
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public methods other than the ones in the interface.
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*)
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inherit color_printing
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inherit black_white_printing
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inherit scanner
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inherit fax number
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method scan_document docfile =
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printf "Scanning [%s] with a multifunctional\n" docfile
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method send_document docfile destination_number =
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printf
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"Sending [%s] from #%s to fax #%s through a multifunctional\n"
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docfile
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phone_number
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destination_number
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method private print_b_and_w docfile =
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printf
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"Printing [%s] in black and white using a multifunctional\n"
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docfile
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method private print_color docfile =
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printf "Printing [%s] in CYMK color using a multifunctional\n" docfile
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method print ?(use_color = true) docfile =
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if use_color then self#print_color docfile else self#print_b_and_w docfile
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end
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let _ =
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let compaq_bw = new bw_printer in
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let epson_color = new color_printer in
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let epson_mf = new multifunctional_printer "664-934-1295" in
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compaq_bw#print_b_and_w "2024report.xlsx";
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epson_color#print_color "wedding_album.pdf";
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epson_mf#print ~use_color:false "essat.docx";
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epson_mf#send_document "private_letter.txt" "55-676-2424";
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epson_mf#scan_document "ocr_test.jpg"
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;;

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