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Use scala-cli in Getting Started page #3072

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153 changes: 142 additions & 11 deletions _overviews/getting-started/install-scala.md
Original file line number Diff line number Diff line change
Expand Up @@ -100,7 +100,8 @@ Run the following command in your terminal, following the on-screen instructions
Check your setup with the command `scala -version`, which should output:
```bash
$ scala -version
Scala code runner version {{site.scala-3-version}} -- Copyright 2002-2022, LAMP/EPFL
Scala code runner version: 1.4.3
Scala version (default): {{site.scala-3-version}}
```
{% endaltDetails %}
<!-- end Alternative Detail -->
Expand Down Expand Up @@ -144,6 +145,146 @@ To install them manually:
or [AdoptOpenJDK 8/11](https://adoptopenjdk.net/). Refer to [JDK Compatibility](/overviews/jdk-compatibility/overview.html) for Scala/Java compatibility detail.
1. Install [sbt](https://www.scala-sbt.org/download.html)

## Using the Scala CLI

In a directory of your choice, which we will call `<project-dir>`, create a file named `hello.scala` with the following code:
```scala
//> using scala {{site.scala-3-version}}

@main
def hello(): Unit =
println("Hello, World!")
```

You can define a method with the `def` keyword and mark it as a "main" method with the `@main` annotation, designating it as
the entry point in program execution. The method's type is `Unit`, which means it does not return a value. `Unit`
can be thought of as an analogue to the `void` keyword found in other languages. The `println` method will print the `"Hello, World!"`
string to standard output.

To run the program, execute `scala run hello.scala` command from a terminal, within the `<project-dir>` directory. The file will be compiled and executed, with console output
similar to following:
```
$ scala run hello.scala
Compiling project (Scala {{site.scala-3-version}}, JVM (20))
Compiled project (Scala {{site.scala-3-version}}, JVM (20))
Hello, World!
```

### Handling command-line arguments

Rewrite the `hello.scala` file so that the program greets the person running it.
```scala
//> using scala {{site.scala-3-version}}

@main
def hello(name: String): Unit =
println(s"Hello, $name!")
```

The `name` argument is expected to be provided when executing the program, and if it's not found, the execution will fail.
The `println` method receives an interpolated string, as indicated by the `s` letter preceding its content. `$name` will be substituted by
the content of the `name` argument.

To pass the arguments when executing the program, put them after `--`:
```
$ scala run hello.scala -- Gabriel
Compiling project (Scala {{site.scala-3-version}}, JVM (20))
Compiled project (Scala {{site.scala-3-version}}, JVM (20))
Hello, Gabriel!
```

You can read more about [main methods](/scala3/book/methods-main-methods.html) and [string interpolation](/scala3/book/string-interpolation.html) in the Scala Book.

### Adding dependencies

We now write a program that will count the files and directories present in its working directory.
We use the [os-lib](https://github.com/com-lihaoyi/os-lib) library from the [Scala toolkit](toolkit/introduction.html)
for that purpose. A dependency on the library can be added with the `//> using` directive. Put the following code in `counter.scala`.
```scala
//> using scala {{site.scala-3-version}}
//> using dep "com.lihaoyi::os-lib:0.10.7"

@main
def countFiles(): Unit =
val paths = os.list(os.pwd)
println(paths.length)
```

In the code above, `os.pwd` returns the current working directory. We pass it to `os.list`, which returns a sequence
of paths directly within the directory passed as an argument. We use a `val` to declare an immutable value, in this example storing the
sequence of paths.

Execute the program. The dependency will be automatically downloaded. The execution should result in a similar output:
```
$ scala run counter.scala
Compiling project (Scala {{site.scala-3-version}}, JVM (20))
Compiled project (Scala {{site.scala-3-version}}, JVM (20))
4
```
The printed number should be 4: `hello.scala`, `counter.scala` and two hidden directories created automatically when a program is executed:
`.bsp` containing information about project used by IDEs, and `.scala-build` containing the results of compilation.

As it turns out, the `os-lib` library is a part of Scala Toolkit, a collection of libraries recommended for tasks like testing,
operating system interaction or handling JSONs. You can read more about the libraries included in the toolkit [here](/toolkit/introduction.html).
To include the toolkit libraries, use the `//> using toolkit 0.5.0` directive:
```scala
//> using scala {{site.scala-3-version}}
//> using toolkit 0.5.0

@main
def countFiles(): Unit =
val paths = os.list(os.pwd)
println(paths.length)
```

This program is identical to the one above. However, other toolkit libraries will also be available to use, should you need them.

### Using the REPL

You can execute code interactively using the REPL provided by the `scala` command. Execute `scala` in the console without any arguments.
```
$ scala
Welcome to Scala {{site.scala-3-version}} (20-ea, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.

scala>
```

Write a line of code to be executed and press enter.
```
scala> println("Hello, World!")
Hello, World!

scala>
```

The result will be printed immediately after executing the line. You can declare values:
```
scala> val i = 1
val i: Int = 1

scala>
```

A new value of type `Int` has been created. If you provide an expression that can be evaluated, its result will be stored in an automatically created value.
```
scala> i + 3
val res0: Int = 4

scala>
```
You can exit the REPL with `:exit`.

### Next steps

Now that you have tasted a little bit of Scala, you can either explore the language itself, or learn how to set up a project using the
sbt and an IDE using the tutorials below. If you want to familiarize yourself with the language more, consider checking out:

* [The Scala Book](/scala3/book/introduction.html) (see the Scala 2 version [here](/overviews/scala-book/introduction.html)), which provides a set of short lessons introducing Scala’s main features.
* [The Tour of Scala](/tour/tour-of-scala.html) for bite-sized introductions to Scala's features.
* [Learning Resources](/learn.html), which includes online interactive tutorials and courses.
* [Our list of some popular Scala books](/books.html).

## Create a "Hello World" project with sbt

Once you have installed sbt, you are ready to create a Scala project, which
Expand Down Expand Up @@ -227,15 +368,5 @@ Otherwise, you can run the application from a terminal with these steps:
When you’re finished experimenting with this project, press `[Enter]` to interrupt the `run` command.
Then type `exit` or press `[Ctrl+D]` to exit sbt and return to your command line prompt.

## Next Steps

Once you've finished the above tutorials, consider checking out:

* [The Scala Book](/scala3/book/introduction.html) (see the Scala 2 version [here](/overviews/scala-book/introduction.html)), which provides a set of short lessons introducing Scala’s main features.
* [The Tour of Scala](/tour/tour-of-scala.html) for bite-sized introductions to Scala's features.
* [Learning Resources](/learn.html), which includes online interactive tutorials and courses.
* [Our list of some popular Scala books](/books.html).
* [The migration guide](/scala3/guides/migration/compatibility-intro.html) helps you to migrate your existing Scala 2 code base to Scala 3.

## Getting Help
There are a multitude of mailing lists and real-time chat rooms in case you want to quickly connect with other Scala users. Check out our [community](https://scala-lang.org/community/) page for a list of these resources, and for where to reach out for help.
3 changes: 1 addition & 2 deletions _overviews/scala-book/two-types-variables.md
Original file line number Diff line number Diff line change
Expand Up @@ -94,8 +94,7 @@ object Hello3 extends App {
As before:

- Save that code in a file named *Hello3.scala*
- Compile it with `scalac Hello3.scala`
- Run it with `scala Hello3`
- Compile and run it with `scala run Hello3.scala`



Expand Down
16 changes: 7 additions & 9 deletions _overviews/scala3-book/methods-main-methods.md
Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,7 @@ Scala 3 offers a new way to define programs that can be invoked from the command
To run this program, save the line of code in a file named as e.g. *Hello.scala*---the filename doesn’t have to match the method name---and run it with `scala`:

```bash
$ scala Hello.scala
$ scala run Hello.scala
Hello, World
```

Expand Down Expand Up @@ -64,10 +64,10 @@ For example, given this `@main` method that takes an `Int`, a `String`, and a va
{% endtab %}
{% endtabs %}

When you compile that code, it creates a main program named `happyBirthday` that’s called like this:
Pass the arguments after `--`:

```
$ scala happyBirthday 23 Lisa Peter
$ scala run happyBirthday.scala -- 23 Lisa Peter
Happy 23rd Birthday, Lisa and Peter!
```

Expand All @@ -79,10 +79,10 @@ The program implemented from an `@main` method checks that there are enough argu
If a check fails, the program is terminated with an error message:

```
$ scala happyBirthday 22
$ scala run happyBirthday.scala -- 22
Illegal command line after first argument: more arguments expected

$ scala happyBirthday sixty Fred
$ scala run happyBirthday.scala -- sixty Fred
Illegal command line: java.lang.NumberFormatException: For input string: "sixty"
```

Expand Down Expand Up @@ -176,11 +176,9 @@ object happyBirthday {
{% endtab %}
{% endtabs %}

If you place that code in a file named *happyBirthday.scala*, you can then compile it with `scalac` and run it with `scala`, as shown previously:
If you place that code in a file named *happyBirthday.scala*, you can then compile and run it with `scala`, as shown previously:

```bash
$ scalac happyBirthday.scala

$ scala happyBirthday 23 Lisa Peter
$ scala run happyBirthday.scala -- 23 Lisa Peter
Happy 23rd Birthday, Lisa and Peter!
```
57 changes: 13 additions & 44 deletions _overviews/scala3-book/taste-hello-world.md
Original file line number Diff line number Diff line change
Expand Up @@ -47,53 +47,23 @@ object hello {
{% endtabs %}
<!-- End tabs -->

Next, compile the code with `scalac`:
Next, compile and run the code with `scala`:

```bash
$ scalac hello.scala
$ scala run 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
The command should produce an output similar to:
```
{% 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
Compiling project (Scala {{site.scala-3-version}}, JVM (20))
Compiled project (Scala {{site.scala-3-version}}, JVM (20))
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.
> The Scala CLI documentation can be found [here](https://scala-cli.virtuslab.org/).

## Ask For User Input

Expand Down Expand Up @@ -152,24 +122,23 @@ use the `+` operator on strings to join `"Hello, "` with `name` and `"!"`, makin

> 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,
Then run the code with `scala`. 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
$ scala run helloInteractive.scala
Compiling project (Scala {{site.scala-3-version}}, JVM (20))
Compiled project (Scala {{site.scala-3-version}}, JVM (20))
Please enter your name:
```

When you enter your name at the prompt, the final interaction should look like this:

```bash
$ scala helloInteractive
$ scala run helloInteractive.scala
Compiling project (Scala {{site.scala-3-version}}, JVM (20))
Compiled project (Scala {{site.scala-3-version}}, JVM (20))
Please enter your name:
Alvin Alexander
Hello, Alvin Alexander!
Expand Down
35 changes: 23 additions & 12 deletions _overviews/tutorials/scala-for-java-programmers.md
Original file line number Diff line number Diff line change
Expand Up @@ -160,38 +160,49 @@ package, so can be accessed from anywhere in a program.

> **Note:** The following assumes you are using Scala on the command line

If we save the above program in a file called
`HelloWorld.scala`, we can run it by issuing the following
command (the greater-than sign `>` represents the shell prompt
and should not be typed):

```shell
> scala run HelloWorld.scala
```

The program will be automatically compiled (with compiled classes somewhere in the newly created `.scala-build` directory)
and executed, producing an output similar to:
```
Compiling project (Scala {{site.scala-3-version}}, JVM (20))
Compiled project (Scala {{site.scala-3-version}}, JVM (20))
Hello, World!
```

#### Compiling From the Command Line

To compile the example, we use `scalac`, the Scala compiler. `scalac`
To compile the example, we use `scala compile` command, which will invoke the Scala compiler, `scalac`. `scalac`
works like most compilers: it takes a source file as argument, maybe
some options, and produces one or several output files. The outputs
it produces are standard Java class files.

If we save the above program in a file called
`HelloWorld.scala`, we can compile it by issuing the following
command (the greater-than sign `>` represents the shell prompt
and should not be typed):

```shell
> scalac HelloWorld.scala
> scala compile HelloWorld.scala -d .
```

This will generate a few class files in the current directory. One of
This will generate a few class files in the current directory (`-d` option sets the compilation output directory). One of
them will be called `HelloWorld.class`, and contains a class
which can be directly executed using the `scala` command, as the
following section shows.

#### Running From the Command Line

Once compiled, a Scala program can be run using the `scala` command.
Once compiled, the program can be run using the `scala run` command.
Its usage is very similar to the `java` command used to run Java
programs, and accepts the same options. The above example can be
programs, and accepts similar options. The above example can be
executed using the following command, which produces the expected
output:

```shell
> scala -classpath . HelloWorld

> scala run --main-class HelloWorld -classpath .
Hello, World!
```

Expand Down
3 changes: 2 additions & 1 deletion _ru/getting-started/index.md
Original file line number Diff line number Diff line change
Expand Up @@ -90,7 +90,8 @@ newcomer_resources:
Проверьте корректность установки с помощью команды `scala -version`, которая должна вывести:
```bash
$ scala -version
Scala code runner version {{site.scala-3-version}} -- Copyright 2002-2022, LAMP/EPFL
Scala code runner version: 1.4.3
Scala version (default): {{site.scala-3-version}}
```
Если сообщение не выдано, возможно, необходимо перезайти в терминал (или перезагрузиться),
чтобы изменения вступили в силу.
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