Ocaml 爆速入門

OCaml爆速入門

レコード

code:ocaml

# type point = {x: int; y: int};;

type point = { x : int; y : int; }

# let origin = {x = 0; y = 0};;

val origin : point = {x = 0; y = 0}

(* ドット記法で値を取り出す *)

# origin.x;;

- : int = 0

# origin.y;;

- : int = 0

(* パターンマッチで値を取り出す *)

# let {x = ox; y = oy } = origin;;

val ox : int = 0

val oy : int = 0

# ox;;

- : int = 0

# oy;;

- : int = 0

# let middle p1 p2 =

{x = (p1.x + p2.x) / 2; y = (p1.y + p2.y) / 2}

;;

val middle : point -> point -> point = <fun>

# middle {x = 10; y = 20} {x = 20; y = 30};;

- : point = {x = 15; y = 25}

ヴァリアントの練習

code:ocaml

# type furikake = Shake | Katsuo | Nori;;

type furikake = Shake | Katsuo | Nori

furikake

ふりかけのデータ型

型 furikake の要素は Shake, Katsuo, Nori の3つ

Shake, Katsuo, Nori はコンストラクタと呼ばれ、大文字で始める必要がある

code:ocaml

# let isVeggie f =

match f with

Shake -> false

| Katsuo -> false

| Nori -> true

;;

# isVeggie Shake;;

- : bool = false

# isVeggie Nori;;

- : bool = true

code:ocaml

# type furikake = Shake | Katsuo | Nori;;

type furikake = Shake | Katsuo | Nori

# type miso = Aka | Shiro | Awase;;

type miso = Aka | Shiro | Awase

# type gu = Wakame | Tofu | Radish;;

type gu = Wakame | Tofu | Radish

# type dish = PorkCutlet | Soup of {m: miso; g: gu} | Rice of furikake;;

type dish = PorkCutlet | Soup of { m : miso; g : gu; } | Rice of furikake

# PorkCutlet;;

- : dish = PorkCutlet

# Soup {m = Aka; g = Tofu};;

- : dish = Soup {m = Aka; g = Tofu}

# Rice Shake;;

- : dish = Rice Shake

# let isSolid d =

match d with

PorkCutlet -> true

| Soup m_and_g -> false

| Rice f -> true

;;

val isSolid : dish -> bool = <fun>

# isSolid PorkCutlet;;

- : bool = true

# isSolid (Soup {m = Shiro; g = Tofu});;

- : bool = false

# isSolid (Rice Shake);;

- : bool = true

料理の値段を計算

とんかつ 350円

味噌汁 90円

ふりかけご飯

シャケ、カツオ 90円

ノリ 80円

code:ocaml

# let priceOfDish d =

match d with

PorkCutlet -> 350

| Soup _ -> 90

| Rice Nori -> 80

| Rice (Shake | Katsuo) -> 90

;;

val priceOfDish : dish -> int = <fun>

# priceOfDish PorkCutlet;;

- : int = 350

# priceOfDish (Soup {m = Awase; g = Tofu});;

- : int = 90

# priceOfDish (Rice Shake);;

- : int = 90

# priceOfDish (Rice Nori);;

- : int = 80

再帰ヴァリアントの練習として定食型(menu型)を作る。

code:ocaml

# type menu = Smile | Add of {d: dish; next: menu};;

type menu = Smile | Add of { d : dish; next : menu; }

(* 注文なし *)

# let m1 = Smile;;

val m1 : menu = Smile

(* トンカツのみ *)

# let m2 = Add {d = PorkCutlet; next = Smile};;

val m2 : menu = Add {d = PorkCutlet; next = Smile}

(* ノリふりかけごはん追加 *)

# let m3 = Add {d = Rice Nori; next = m2};;

val m3 : menu =

Add {d = Rice Nori; next = Add {d = PorkCutlet; next = Smile}}

(* シャケふりかけごはんおかわり *)

# let m4 = Add {d = Rice Shake; next = m3};;

val m4 : menu =

Add

{d = Rice Shake;

next = Add {d = Rice Nori; next = Add {d = PorkCutlet; next = Smile}}}

値段を計算する

code:ocaml

# let rec priceOfMenu m =

match m with

Smile -> 0

| Add { d = d1; next = m' } -> (priceOfDish d1) + (priceOfMenu m')

;;

val priceOfMenu : menu -> int = <fun>

# priceOfMenu m1;;

- : int = 0

# priceOfMenu m2;;

- : int = 350

# priceOfMenu m3;;

- : int = 430

# priceOfMenu m4;;

- : int = 520

変更可能データ構造

code:ocaml