v/README.md

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<h1>The V Programming Language</h1>

[vlang.io](https://vlang.io) |
[Docs](https://github.com/vlang/v/blob/master/doc/docs.md) |
[Changelog](https://github.com/vlang/v/blob/master/CHANGELOG.md) |
[Speed](https://fast.vlang.io/) |
[Contributing & compiler design](https://github.com/vlang/v/blob/master/CONTRIBUTING.md)

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## Key Features of V

- Simplicity: the language can be learned in less than an hour
- Fast compilation: ≈110k loc/s with a Clang backend,
    ≈1 million loc/s with x64 and tcc backends *(Intel i5-7500, SSD, no optimization)* ([demo video](https://www.youtube.com/watch?v=pvP6wmcl_Sc))
- Easy to develop: V compiles itself in less than a second
- Performance: as fast as C (V's main backend compiles to human readable C)
- Safety: no null, no globals, no undefined behavior, immutability by default
- C to V translation
- Hot code reloading
- [Innovative memory management](https://vlang.io/#memory) ([demo video](https://www.youtube.com/watch?v=gmB8ea8uLsM))
- [Cross-platform UI library](https://github.com/vlang/ui)
- Built-in graphics library
- Easy cross compilation
- REPL
- [Built-in ORM](https://github.com/vlang/v/blob/master/doc/docs.md#orm)
- [Built-in web framework](https://github.com/vlang/v/blob/master/vlib/vweb/README.md)
- C and JavaScript backends

## Stability guarantee and future changes

Despite being at an early development stage, the V language is relatively stable and has
backwards compatibility guarantee, meaning that the code you write today is guaranteed
to work a month, a year, or five years from now.

There still may be minor syntax changes before the 1.0 release, but they will be handled
automatically via `vfmt`, as has been done in the past.

The V core APIs (primarily the `os` module) will still have minor changes until
they are stabilized in 2020. Of course the APIs will grow after that, but without breaking
existing code.

Unlike many other languages, V is not going to be always changing, with new features
being introduced and old features modified. It is always going to be a small and simple
language, very similar to the way it is right now.

## Installing V from source

### Linux, macOS, Windows, *BSD, Solaris, WSL, Android, Raspbian

```bash
git clone https://github.com/vlang/v
cd v
make
```

That's it! Now you have a V executable at `[path to V repo]/v`.
`[path to V repo]` can be anywhere.

(On Windows `make` means running `make.bat`, so make sure you use `cmd.exe`)

Now you can try `./v run examples/hello_world.v` (`v.exe` on Windows).

V is constantly being updated. To update V, simply run:

```bash
v up
```

### C compiler

It's recommended to use Clang, GCC, or Visual Studio.
If you are doing development, you most likely already have one of those installed.

Otherwise, follow these instructions:

- [Installing a C compiler on Linux and macOS](https://github.com/vlang/v/wiki/Installing-a-C-compiler-on-Linux-and-macOS)

- [Installing a C compiler on Windows](https://github.com/vlang/v/wiki/Installing-a-C-compiler-on-Windows)

However, if none is found when running `make` on Linux or Windows,
TCC is downloaded as the default C backend.
It's very lightweight (several MB) so this shouldn't take too long.

### Symlinking

NB: it is *highly recommended*, that you put V on your PATH. That saves
you the effort to type in the full path to your v executable every time.
V provides a convenience `v symlink` command to do that more easily.

On Unix systems, it creates a `/usr/local/bin/v` symlink to your
executable. To do that, run:

```bash
sudo ./v symlink
```

On Windows, start a new shell with administrative privileges, for
example by <kbd>Windows Key</kbd>, then type `cmd.exe`, right click on its menu
entry, and choose `Run as administrator`. In the new administrative
shell, cd to the path, where you have compiled v.exe, then type:

```bat
.\v.exe symlink
```

That will make V available everywhere, by adding it to your PATH.
Please restart your shell/editor after that, so that it can pick
the new PATH variable.

NB: there is no need to run `v symlink` more than once - v will
continue to be available, even after `v up`, restarts and so on.
You only need to run it again, if you decide to move the V repo
folder somewhere else.

### Docker

<details><summary>Expand Docker instructions</summary>

```bash
git clone https://github.com/vlang/v
cd v
docker build -t vlang .
docker run --rm -it vlang:latest
```

### Docker with Alpine/musl

```bash
git clone https://github.com/vlang/v
cd v
docker build -t vlang --file=Dockerfile.alpine .
docker run --rm -it vlang:latest
```

</details>

### Testing and running the examples

Make sure V can compile itself:

```bash
v self
```

```bash
$ v
V 0.2.x
Use Ctrl-C or `exit` to exit

>>> println('hello world')
hello world
>>>
```

```bash
cd examples
v hello_world.v && ./hello_world    # or simply
v run hello_world.v                 # this builds the program and runs it right away

v word_counter.v && ./word_counter cinderella.txt
v run news_fetcher.v
v run tetris/tetris.v
```

<img src='https://raw.githubusercontent.com/vlang/v/master/examples/tetris/screenshot.png' width=300>

NB: In order to build Tetris or 2048 (or anything else using `sokol` or  `gg` graphics modules)
on some Linux systems, you need to install `libxi-dev` and `libxcursor-dev` .

If you plan to use the http package, you also need to install OpenSSL on non-Windows systems.

```bash
macOS:
brew install openssl

Debian/Ubuntu:
sudo apt install libssl-dev

Arch/Manjaro:
openssl is installed by default

Fedora:
sudo dnf install openssl-devel
```

## V sync
V's `sync` module and channel implementation uses libatomic.
It is most likely already installed on your system, but if not,
you can install it, by doing the following:
```bash
MacOS: already installed

Debian/Ubuntu:
sudo apt install libatomic1

Fedora/CentOS/RH:
sudo dnf install libatomic-static
```

## V UI

<a href="https://github.com/vlang/ui">
<img src='https://raw.githubusercontent.com/vlang/ui/master/examples/screenshot.png' width=712>
</a>

https://github.com/vlang/ui

<!---
## JavaScript backend

[examples/hello_v_js.v](examples/hello_v_js.v):

```v
fn main() {
	for i in 0 .. 3 {
		println('Hello from V.js')
	}
}
```

```bash
v -o hi.js examples/hello_v_js.v && node hi.js
Hello from V.js
Hello from V.js
Hello from V.js
```
-->

## Android graphical apps

With V's `vab` tool, building V UI and graphical apps for Android can become as easy as:

```
./vab /path/to/v/examples/2048
```

[https://github.com/vlang/vab](https://github.com/vlang/vab).

<img src="https://user-images.githubusercontent.com/768942/107622846-c13f3900-6c58-11eb-8a66-55db12979b73.png">

## Developing web applications

Check out the [Building a simple web blog](https://github.com/vlang/v/blob/master/tutorials/building_a_simple_web_blog_with_vweb/README.md)
tutorial and Gitly, a light and fast alternative to GitHub/GitLab:

https://github.com/vlang/gitly

<img src="https://user-images.githubusercontent.com/687996/85933714-b195fe80-b8da-11ea-9ddd-09cadc2103e4.png">

## Troubleshooting

Please see the [Troubleshooting](https://github.com/vlang/v/wiki/Troubleshooting) section on our [wiki page](https://github.com/vlang/v/wiki)

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