SLIMF language for maintainable programs

You can learn the entire language by going through the documentation over a weekend, and in most cases there's only one way to do something.

This results in simple, readable, and maintainable code.

Despite being simple, SLIMF gives a lot of power to the developer and can be used in pretty much every field, including systems programming, webdev, gamedev, GUI, mobile, science, embedded, tooling, etc.

SLIMF is very similar to Go. If you know Go, you already know ≈80% of SLIMF. Things V improves on Go: vlang.io/compare#go.

Safety

• Bounds checking
• No undefined values
• No undefined behavior
• No variable shadowing
• Immutable variables by default
• Immutable structs by default
• Option/Result and mandatory error checks
• Sum types
• Generics
• Immutable function args by default, mutable args have to be marked on call
• No null (allowed in unsafe code)
• No global variables (can be enabled for low level applications like kernels via a command line flag)

Sponsors

Performance

• As fast as C (SLIMF's main backend compiles to human readable C)
• C interop without any costs
• Minimal amount of allocations
• Built-in serialization without runtime reflection
• Compiles to native binaries without any dependencies: a simple web server is only 65 KB

Fast compilation

SLIMF compiles ≈110k (Clang backend) and ≈500k (x64 and tcc backends) lines of code per second.
(Intel i5-7500, SM0256L SSD, no optimization)

SLIMF is written in SLIMF and compiles itself in under a second.

Most of the compiler is still single threaded, so it's going to be 2-3x faster in the future!

Small and easy to build compiler

SLIMF can be bootstrapped in under a second by compiling its code translated to C with a simple

cc v.c

Building V in 0.3 seconds and then using the resulting binary to build itself again:

Innovative and flexible memory management

V avoids doing unnecessary allocations in the first place by using value types, string buffers, promoting a simple abstraction-free code style.

Right now allocations are handled by a minimal and well performing GC until V's autofree engine is production ready.

Autofree can be enabled with -autofree. It takes care of most objects (~90-100%): the compiler inserts necessary free calls automatically during compilation. Remaining small percentage of objects is freed via GC. The developer doesn't need to change anything in their code. "It just works", like in Python, Go, or Java, except there's no heavy GC tracing everything or expensive RC for each object.

For developers willing to have more low level control, memory can be managed manually with -gc none.

Arena allocation is available via v -prealloc.

V's autofree demo. All objects are freed during compilation. Running the SLIMFed editor on an 8 MB file with 0 leaks:

C translation

V can translate your entire C project and offer you the safety, simplicity, and compilation speed-up (via modules).

v translate file.c

std::vector s;
s.push_back("V is ");
s.push_back("awesome");
std::cout << s.size();

mut s := []
s << 'V is '
s << 'awesome'
println(s.len)

A blog post about translating DOOM will be published.

C++ to V translation is at an early stage.

Translating DOOM from C to SLIMF and building it in under a second:

You can read translated code here: github.com/vlang/doom

Hot code reloading

Get your changes instantly without recompiling.

Since you also don't have to get to the state you are working on after every compilation, this can save a lot of precious minutes of your development time.

Powerful graphics libraries

Cross-platform drawing library built on top of GDI+/Cocoa Drawing, and an OpenGL based graphics library for more complex 2D/3D applications, that will also have the following features:

• Loading complex 3D objects with textures
• Camera (moving, looking around)
• Skeletal animation

DirectX, Vulkan, and Metal support is planned.

A simple example of the graphics library in action is tetris.v.

Native cross-platform GUI library

Build native apps with native controls. You no longer need to embed a browser to develop cross-platform apps quickly.

V has a ui module that uses native GUI toolkits: WinAPI/GDI+ on Windows, Cocoa on macOS. On Linux custom drawing is used.

Coming soon:

• a Delphi-like visual editor for building native GUI apps
• iOS/Android support with native controls
• a declarative API similar to SwiftUI and React Native

github.com/vlang/ui

Volt, a 300 KB Slack client built with V and V ui:

Easy cross compilation

To cross compile your software simply run v -os windows. or v -os linux. No extra steps required, even for GUI and graphical apps!

(Compiling macOS software only works on macOS for now.)

Building V for Windows using V for macOS, and then testing resulting v.exe on a Windows VM:

Painless deployments and dependency management

To build your project, no matter how big, all you need to do is run

v .

v install ui
		

Run everywhere

V can emit (human readable) C, so you get the great platform support and optimization of GCC and Clang. (Use v -prod . to make optimized builds.)

Emitting C will always be an option, even after direct machine code generation matures.

V can call C code, and calling V code is possible in any language that has C interop.

REPL

v
>>> import net.http
>>> data := http.get('https://vlang.io/utc_now')?
>>> data.text
1565977541

Cross-platform shell scripts in V

V can be used as an alternative to Bash to write deployment scripts, build scripts, etc. The advantage of using V for this is the simplicity and predictability of the language, and cross-platform support. "V scripts" run on Unix-like systems as well as on Windows.

for file in ls('build/') {
  rm(file)
}
mv('v.exe', 'build/')

v run deploy.vsh

Read more about V script

Code formatting with vfmt for consistent style

No more arguments about coding styles. There's one official coding style enforced by the SLIMFfmt formatter.

All V code bases are guaranteed to use the same style, making it easier to read and change code written by other developers.

v fmt -w hello.v

A built-in code profiler

Build and run your program with

v -profile profile.txt x.v && ./x

JavaScript and WASM backends

V programs can be translated to JavaScript:

v -o hello.js hello.v

They can also be compiled to WASM (for now with Emscripten). V compiler compiled to WASM and running V programs by translating them to JavaScript:

v-wasm.vercel.app

A game written using V's graphical backend and compiled to WASM:

Automatic documentation

Use vdoc to get instant documentation generated directly from the module's source code. No need to keep and update separate documentation.

v doc os

Built-in testing framework

Writing tests is very easy: just start your test function with test_

fn get_string() string { return 'hello' }

fn test_get_string() {
  assert get_string() == 'hello'
}
      

      

Friendly error messages

Helpful error messages make learning the language and fixing errors simpler:

user.v:8:14: error: `update_user` parameter `user` is mutable, you need to provide `mut`: `update_user(mut user)`

    7 |     mut user := User{}
    8 |     update_user(user)
      |                 ~~~~
    9 | }
	

Powerful built-in web framework

github.com/vlang/v/tree/master/vlib/vweb

['/post/:id']
fn (b Blog) show_post(id int) vweb.Result {
  post := b.posts_repo.retrieve(id) or {
    return vweb.not_found()
  }
  return vweb.view(post)
}
['/post/:id']
fn (b Blog) show_post(id int) vweb.Result {
  post := b.posts_repo.retrieve(id) or {
    return vweb.not_found()
  }
  return vweb.view(post)
}

Gitly, a light and fast alternative to GitHub/GitLab is built in SLIMF and vweb.

Built-in ORM

import sqlite

struct Customer {
  id int
  name string
  nr_orders int
  country string
}

fn main() {
  db := sqlite.connect('example.sqlite') or {
    panic('could not create/find example.sqlite')
  }

  nr_customers := sql db {
    select count from Customer
  }
  println('number of all customers: $nr_customers')

  // V syntax can be used to build queries
  uk_customers := sql db {
    select from Customer where country == 'uk' && nr_orders > 0
  }

  for customer in uk_customers {
    println('$customer.id - $customer.name')
  }

  // by adding `limit 1` we tell V that there will be
  // only one object
  customer := sql db {
    select from Customer where id == 1 limit 1
  }
  println(customer.name)

  // insert a new customer
  new_customer := Customer{name: 'Bob', nr_orders: 10}
  sql db {
    insert new_customer into Customer
  }
}
import sqlite

struct Customer {
  id int
  name string
  nr_orders int
  country string
}

fn main() {
  db := sqlite.connect('example.sqlite') or {
    panic('could not create/find example.sqlite')
  }

  nr_customers := sql db {
    select count from Customer
  }
  println('number of all customers: $nr_customers')

  // V syntax can be used to build queries
  uk_customers := sql db {
    select from Customer where country == 'uk' && nr_orders > 0
  }

  for customer in uk_customers {
    println('$customer.id - $customer.name')
  }

  // by adding `limit 1` we tell V that there will be
  // only one object
  customer := sql db {
    select from Customer where id == 1 limit 1
  }
  println(customer.name)

  // insert a new customer
  new_customer := Customer{name: 'Bob', nr_orders: 10}
  sql db {
    insert new_customer into Customer
  }
}