Add scala 3 book in russian

Author: artemkorsakov

_overviews/scala3-book/ca-context-bounds.md

@@ -5,7 +5,6 @@ description: This page demonstrates Context Bounds in Scala 3.
 num: 61
 previous-page: types-type-classes
 next-page: ca-given-imports
-languages: [ru]
 ---
 
 

_overviews/scala3-book/taste-hello-world.md

@@ -5,6 +5,7 @@ description: This section demonstrates a Scala 3 'Hello, World!' example.
 num: 5
 previous-page: taste-intro
 next-page: taste-repl
+languages: [ru]
 ---
 
 > **Hint**: in the following examples try picking your preferred Scala version.

_ru/scala3/book/taste-hello-world.md

@@ -0,0 +1,201 @@
+---
+layout: multipage-overview
+title: Пример 'Hello, World!'
+scala3: true
+partof: scala3-book
+overview-name: "Scala 3 — Book"
+type: chapter
+description: В этом примере демонстрируется пример 'Hello, World!' на Scala 3.
+language: ru
+num: 5
+previous-page: taste-intro
+next-page:
+---
+
+> **Hint**: in the following examples try picking your preferred Scala version.
+> <noscript><span style="font-weight: bold;">Info</span>: JavaScript is currently disabled, code tabs will still work, but preferences will not be remembered.</noscript>
+
+## Your First Scala Program
+
+
+A Scala “Hello, World!” example goes as follows.
+First, put this code in a file named _hello.scala_:
+
+
+<!-- Display Hello World for each Scala Version -->
+{% tabs hello-world-demo class=tabs-scala-version %}
+
+{% tab 'Scala 2' for=hello-world-demo %}
+```scala
+object hello {
+  def main(args: Array[String]) = {
+    println("Hello, World!")
+  }
+}
+```
+> In this code, we defined a method named `main`, inside a Scala `object` named `hello`.
+> An `object` in Scala is similar to a `class`, but defines a singleton instance that you can pass around.
+> `main` takes an input parameter named `args` that must be typed as `Array[String]`, (ignore `args` for now).
+
+{% endtab %}
+
+{% tab 'Scala 3' for=hello-world-demo %}
+```scala
+@main def hello() = println("Hello, World!")
+```
+> In this code, `hello` is a method.
+> It’s defined with `def`, and declared to be a “main” method with the `@main` annotation.
+> It prints the `"Hello, World!"` string to standard output (STDOUT) using the `println` method.
+
+{% endtab %}
+
+{% endtabs %}
+<!-- End tabs -->
+
+Next, compile the code with `scalac`:
+
+```bash
+$ scalac hello.scala
+```
+
+If you’re coming to Scala from Java, `scalac` is just like `javac`, so that command creates several files:
+
+<!-- Display Hello World compiled outputs for each Scala Version -->
+{% tabs hello-world-outputs class=tabs-scala-version %}
+
+{% tab 'Scala 2' for=hello-world-outputs %}
+```bash
+$ ls -1
+hello$.class
+hello.class
+hello.scala
+```
+{% endtab %}
+
+{% tab 'Scala 3' for=hello-world-outputs %}
+```bash
+$ ls -1
+hello$package$.class
+hello$package.class
+hello$package.tasty
+hello.scala
+hello.class
+hello.tasty
+```
+{% endtab %}
+
+{% endtabs %}
+<!-- End tabs -->
+
+Like Java, the _.class_ files are bytecode files, and they’re ready to run in the JVM.
+
+Now you can run the `hello` method with the `scala` command:
+
+```bash
+$ scala hello
+Hello, World!
+```
+
+Assuming that worked, congratulations, you just compiled and ran your first Scala application.
+
+> More information about sbt and other tools that make Scala development easier can be found in the [Scala Tools][scala_tools] chapter.
+
+## Ask For User Input
+
+In our next example let's ask for the user's name before we greet them!
+
+There are several ways to read input from a command-line, but a simple way is to use the
+`readLine` method in the _scala.io.StdIn_ object. To use it, you need to first import it, like this:
+
+{% tabs import-readline %}
+{% tab 'Scala 2 and 3' for=import-readline %}
+```scala
+import scala.io.StdIn.readLine
+```
+{% endtab %}
+{% endtabs %}
+
+To demonstrate how this works, let’s create a little example. Put this source code in a file named _helloInteractive.scala_:
+
+<!-- Display interactive Hello World application for each Scala Version -->
+{% tabs hello-world-interactive class=tabs-scala-version %}
+
+{% tab 'Scala 2' for=hello-world-interactive %}
+```scala
+import scala.io.StdIn.readLine
+
+object helloInteractive {
+
+  def main(args: Array[String]) = {
+    println("Please enter your name:")
+    val name = readLine()
+
+    println("Hello, " + name + "!")
+  }
+
+}
+```
+{% endtab %}
+
+{% tab 'Scala 3' for=hello-world-interactive %}
+```scala
+import scala.io.StdIn.readLine
+
+@main def helloInteractive() =
+  println("Please enter your name:")
+  val name = readLine()
+
+  println("Hello, " + name + "!")
+```
+{% endtab %}
+
+{% endtabs %}
+<!-- End tabs -->
+
+In this code we save the result of `readLine` to a variable called `name`, we then
+use the `+` operator on strings to join `"Hello, "` with `name` and `"!"`, making one single string value. 
+
+> You can learn more about using `val` by reading [Variables and Data Types](/scala3/book/taste-vars-data-types.html).
+
+Then compile the code with `scalac`:
+
+```bash
+$ scalac helloInteractive.scala
+```
+Then run it with `scala helloInteractive`, this time the program will pause after asking for your name,
+and wait until you type a name and press return on the keyboard, looking like this:
+
+```bash
+$ scala helloInteractive
+Please enter your name:
+▌
+```
+
+When you enter your name at the prompt, the final interaction should look like this:
+
+```bash
+$ scala helloInteractive
+Please enter your name:
+Alvin Alexander
+Hello, Alvin Alexander!
+```
+
+### A Note about Imports
+
+As you saw in this application, sometimes certain methods, or other kinds of definitions that we'll see later,
+are not available unless you use an `import` clause like so:
+
+{% tabs import-readline-2 %}
+{% tab 'Scala 2 and 3' for=import-readline-2 %}
+```scala
+import scala.io.StdIn.readLine
+```
+{% endtab %}
+{% endtabs %}
+
+Imports help you write code in a few ways:
+  - you can put code in multiple files, to help avoid clutter, and to help navigate large projects.
+  - you can use a code library, perhaps written by someone else, that has useful functionality
+  - you can know where a certain definition comes from (especially if it was not written in the current file).
+
+[scala_tools]: {% link _overviews/scala3-book/scala-tools.md %}

_ru/scala3/book/taste-intro.md

@@ -9,7 +9,7 @@ description: В этой главе представлен общий обзор
 language: ru
 num: 4
 previous-page: why-scala-3
-next-page:
+next-page: taste-hello-world
 ---