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 over the course of a weekend
- Fast compilation: ≈110k loc/s with a Clang backend,
  ≈500k loc/s with native 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 (wip), immutability by default
- C to V translation ([Translating DOOM demo video](https://www.youtube.com/watch?v=6oXrz3oRoEg))
- Hot code reloading
- [Flexible memory management](https://vlang.io/#memory). GC by default, manual via `v -gc none`,
  arena allocation via `v -prealloc`, autofree via `v -autofree`
  ([autofree 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
- Great for writing low-level software ([Vinix OS](https://github.com/vlang/vinix))

## 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 V 1.0. 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

--> **_(this is the preferred method)_**

### Linux, macOS, Windows, *BSD, Solaris, WSL, etc.

Usually, installing V is quite simple if you have an environment that already has a
functional `git` installation.

To get started, simply try to execute the following in your terminal/shell:

```bash
git clone https://github.com/vlang/v
cd v
make
# HINT: Using Windows? run make.bat in a cmd shell, or ./make.bat in PowerShell
```

That should be it and you should find your V executable at `[path to V repo]/v`.
`[path to V repo]` can be anywhere.

(As in the hint above, on Windows `make` means running `make.bat`.)

Now you can try `./v run examples/hello_world.v` (or `v run examples/hello_world.v` in cmd shell).

* *Trouble? Please see the note above and link to
  [Installation Issues](https://github.com/vlang/v/discussions/categories/installation-issues)
  for help.*

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

```bash
v up
```

> **Note**
> If you run into any trouble, or you have a different operating
> system or Linux distribution that doesn't install or work immediately, please see
> [Installation Issues](https://github.com/vlang/v/discussions/categories/installation-issues)
> and search for your OS and problem.
>
> If you can't find your problem, please add it to an existing discussion if one exists for
> your OS, or create a new one if a main discussion doesn't yet exist for your OS.

### C compiler

The [Tiny C Compiler (tcc)](https://repo.or.cz/w/tinycc.git) is downloaded for you by `make` if
there is a compatible version for your system, and installed under the V `thirdparty` directory.

This compiler is very fast, but does almost no optimizations. It is best for development builds.

For production builds (using the `-prod` option to V), it's recommended to use clang, gcc, or
Microsoft Visual C++. 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)

### Symlinking

> **Note**
> 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 pressing the
<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, then
type:

```bat
v symlink
```

(or `./v symlink` in PowerShell)

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

> **Note**
> There is no need to run `v symlink` more than once - v will still 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.

### Void Linux

<details><summary>Expand Void Linux instructions</summary>

```bash
# xbps-install -Su base-devel
# xbps-install libatomic-devel
$ git clone https://github.com/vlang/v
$ cd v
$ make
```

</details>

### 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>

### Termux/Android

On Termux, V needs some packages preinstalled - a working C compiler, also `libexecinfo`,
`libgc` and `libgc-static`. After installing them, you can use the same script, like on
Linux/macos:

```bash
pkg install clang libexecinfo libgc libgc-static make git
git clone https://github.com/vlang/v
cd v
make
```

## Testing and running the examples

Make sure V can compile itself:

```bash
$ v self
$ v
V 0.3.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 run word_counter/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 alt='tetris screenshot'>

In order to build Tetris or 2048 (or anything else using `sokol` or `gg` graphics modules),
you will need additional development libraries for your system.

| System              | Installation method                                                                                |
|---------------------|----------------------------------------------------------------------------------------------------|
| Debian/Ubuntu based | `sudo apt install libxi-dev libxcursor-dev libgl-dev`                                                        |
| Fedora/RH/CentOS    | `sudo dnf install libXcursor-devel libXi-devel libX11-devel libglvnd-devel`                        |
| NixOS               | add `xorg.libX11.dev xorg.libXcursor.dev xorg.libXi.dev libGL.dev` to `environment.systemPackages` |

## V net.http, net.websocket, `v install`

The net.http module, the net.websocket module, and the `v install` command may all use SSL.
V comes with a version of mbedtls, which should work on all systems. If you find a need to
use OpenSSL instead, you will need to make sure that it is installed on your system, then
use the `-d use_openssl` switch when you compile.

To install OpenSSL on non-Windows systems:

| System              | Installation command             |
|---------------------|----------------------------------|
| macOS               | `brew install openssl`           |
| Debian/Ubuntu based | `sudo apt install libssl-dev`    |
| Arch/Manjaro        | openssl is installed by default  |
| Fedora/CentOS/RH    | `sudo dnf install openssl-devel` |

On Windows, OpenSSL is simply hard to get working correctly. The instructions
[here](https://tecadmin.net/install-openssl-on-windows/) may (or may not) help.

## 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:

| System              | Installation command                |
|---------------------|-------------------------------------|
| macOS               | already installed                   |
| Debian/Ubuntu based | `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 alt='V UI example screenshot'>
</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" alt="vab examples screenshot">

## 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" alt="gitly screenshot">

## Vinix, an OS/kernel written in V

V is great for writing low-level software like drivers and kernels.
Vinix is an OS/kernel that already runs bash, GCC, V, and nano.

https://github.com/vlang/vinix

<img src="https://github.com/vlang/vinix/blob/main/screenshot0.png?raw=true" alt="vinix screenshot 1">
<img src="https://github.com/vlang/vinix/blob/main/screenshot1.png?raw=true" alt="vinix screenshot 2">

## Acknowledgement

V thanks Fabrice Bellard for his original work on the
[TCC - Tiny C Compiler](https://bellard.org/tcc/).
Note the TCC website is old; the current TCC repository can be found
[here](https://repo.or.cz/w/tinycc.git).
V utilizes pre-built TCC binaries located at
[https://github.com/vlang/tccbin/](https://github.com/vlang/tccbin/).

## 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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