JavaScript にコンパイルされる 10 の興味深い言語

// Example extracted from dartlang.org

import 'dart:async';
import 'dart:math' show Random;

main() async {
  print('Compute π using the Monte Carlo method.');
  await for (var estimate in computePi()) {
    print('π ≅ $estimate');
  }
}

/// Generates a stream of increasingly accurate estimates of π.
Stream<double> computePi({int batch: 1000000}) async* {
  var total = 0;
  var count = 0;
  while (true) {
    var points = generateRandom().take(batch);
    var inside = points.where((p) => p.isInsideUnitCircle);
    total += batch;
    count += inside.length;
    var ratio = count / total;
    // Area of a circle is A = π⋅r², therefore π = A/r².
    // So, when given random points with x ∈ <0,1>,
    // y ∈ <0,1>, the ratio of those inside a unit circle
    // should approach π / 4. Therefore, the value of π
    // should be:
    yield ratio * 4;
  }
}

Iterable<Point> generateRandom([int seed]) sync* {
  final random = new Random(seed);
  while (true) {
    yield new Point(random.nextDouble(), random.nextDouble());
  }
}

class Point {
  final double x, y;
  const Point(this.x, this.y);
  bool get isInsideUnitCircle => x * x + y * y <= 1;
}

class Person {
  private name: string;
  private age: number;
  private salary: number;

  constructor(name: string, age: number, salary: number) {
    this.name = name;
    this.age = age;
    this.salary = salary;
  }

  toString(): string {
    return `${this.name} (${this.age}) (${this.salary})`;
  }
}

module Main exposing (..)

import Html exposing (..)


-- MAIN


main : Program Never Model Msg
main =
    Html.program
        { init = init
        , update = update
        , view = view
        , subscriptions = subscriptions
        }



-- INIT


type alias Model = String


init : ( Model, Cmd Msg )
init = ( "Hello World!", Cmd.none )


-- UPDATE


type Msg
    = DoNothing


update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
    case msg of
        DoNothing ->
            ( model, Cmd.none )


-- VIEW


view : Model -> Html Msg
view model =
    div [] [text model]


-- SUBSCRIPTIONS


subscriptions : Model -> Sub Msg
subscriptions model =
    Sub.none

module Main where

import Prelude
import Data.Foldable (fold)
import TryPureScript

main =
    render $ fold
      [ h1 (text "Try PureScript!")
      , p (text "Try out the examples below, or create your own!")
      , h2 (text "Examples")
      , list (map fromExample examples)
      ]
  where
    fromExample { title, gist } =
      link ("?gist=" <> gist) (text title)

    examples =
      [ { title: "Algebraic Data Types"
        , gist: "37c3c97f47a43f20c548"
        }
      , { title: "Loops"
        , gist: "cfdabdcd085d4ac3dc46"
        }
      , { title: "Operators"
        , gist: "3044550f29a7c5d3d0d0"
        }
      ]

# Assignment:
number   = 42
opposite = true

# Conditions:
number = -42 if opposite

# Functions:
square = (x) -> x * x

# Arrays:
list = [1, 2, 3, 4, 5]

# Objects:
math =
  root:   Math.sqrt
  square: square
  cube:   (x) -> x * square x

# Splats:
race = (winner, runners...) ->
  print winner, runners

# Existence:
alert "I knew it!" if elvis?

# Array comprehensions:
cubes = (math.cube num for num in list)

; Extracted from https://github.com/clojure/clojurescript/blob/master/samples/dom/src/dom/test.cljs

(ns dom.test
  (:require [clojure.browser.event :as event]
            [clojure.browser.dom   :as dom]))

(defn log [& args]
  (.log js/console (apply pr-str args)))

(defn log-obj [obj]
  (.log js/console obj))

(defn log-listener-count []
  (log "listener count: " (event/total-listener-count)))

(def source      (dom/get-element "source"))
(def destination (dom/get-element "destination"))

(dom/append source
            (dom/element "Testing me ")
            (dom/element "out!"))

(def success-count (atom 0))

(log-listener-count)

(event/listen source
              :click
              (fn [e]
                (let [i (swap! success-count inc)
                      e (dom/element :li
                                     {:id "testing"
                                      :class "test me out please"}
                                     "It worked!")]
                  (log-obj e)
                  (log i)
                  (dom/append destination
                              e))))

(log-obj (dom/element "Text node"))
(log-obj (dom/element :li))
(log-obj (dom/element :li {:class "foo"}))
(log-obj (dom/element :li {:class "bar"} "text node"))
(log-obj (dom/element [:ul [:li :li :li]]))
(log-obj (dom/element :ul [:li :li :li]))
(log-obj (dom/element :li {} [:ul {} [:li :li :li]]))
(log-obj (dom/element [:li {:class "baz"} [:li {:class "quux"}]]))

(log-obj source)
(log-listener-count)

// JavaScript
var xhr = new XMLHttpRequest();

xhr.open("GET",
  "https://api.twitter.com/1.1/search/" +
  "tweets.json?q=%23scalajs"
);
xhr.onload = (e) => {
  if (xhr.status === 200) {
    var r = JSON.parse(xhr.responseText);
    $("#tweets").html(parseTweets(r));
  }
};
xhr.send();

// Scala.js
val xhr = new XMLHttpRequest()

xhr.open("GET",
  "https://api.twitter.com/1.1/search/" +
  "tweets.json?q=%23scalajs"
)
xhr.onload = { (e: Event) =>
  if (xhr.status == 200) {
    val r = JSON.parse(xhr.responseText)
    $("#tweets").html(parseTweets(r))
  }
}
xhr.send()

/* A type variant being pattern matched */

let possiblyNullValue1 = None;
let possiblyNullValue2 = Some "Hello@";

switch possiblyNullValue2 {
| None => print_endline "Nothing to see here."
| Some message => print_endline message
};

/* Parametrized types */

type universityStudent = {gpa: float};
type response 'studentType = {status: int, student: 'studentType};
let result: response universityStudent = fetchDataFromServer ();

/* A simple typed object */

type payload = Js.t {.
  name: string,
  age: int
};
let obj1: payload = {"name": "John", "age": 30};

// Example extracted from http://code.haxe.org

extern class Database {
  function new();
  function getProperty<T>(property:Property<T>):T;
  function setProperty<T>(property:Property<T>, value:T):Void;
}

abstract Property<T>(String) {
  public inline function new(name) {
    this = name;
  }
}

class Main {
  static inline var PLAYER_NAME = new Property<String>("playerName");
  static inline var PLAYER_LEVEL = new Property<Int>("playerLevel");

  static function main() {
    var db = new Database();

    var playerName = db.getProperty(PLAYER_NAME);
    trace(playerName.toUpperCase());

    db.setProperty(PLAYER_LEVEL, 1);
  }
}

# Reverse a string
proc reverse(s: string): string =
  result = ""
  for i in countdown(high(s), 0):
    result.add s[i]

var str1 = "Reverse This!"
echo "Reversed: ", reverse(str1)

# Using templates
template genType(name, fieldname: expr, fieldtype: typedesc) =
  type
    name = object
      fieldname: fieldtype

genType(Test, foo, int)

var x = Test(foo: 4566)
echo(x.foo) # 4566