Vala (programming language)

Vala

Paradigm(s)	Multi-paradigm: imperative, structured, object-oriented
Appeared in	2006
Developer	Jürg Billeter, Raffaele Sandrini
Stable release	0.15.1 (26 January 2012 (2012-01-26))
Typing discipline	static, strong
Influenced by	C, C++, C#, D, Java
OS	cross-platform all supported by GLib
License	LGPL 2.1+
Usual filename extensions	.vala, .vapi
Website	live.gnome.org/Vala

Vala is an object-oriented programming language with a self-hosting compiler that generates C code and uses the GObject system. Vala is syntactically similar to C# and includes useful language features like anonymous functions, signals, properties, generics, assisted memory management, exception handling, type inference, and foreach statements. It is being developed by Jürg Billeter and Raffaele Sandrini. It aims to bring modern language features to C, with no added runtime needs and with little overhead, by targeting the GObject object system. Rather than being compiled directly to assembler or to another intermediate language, Vala is source-to-source compiled to C which is then compiled with a platform's standard C compiler, such as gcc.

For memory management, the GObject system provides reference counting. In C a programmer must manually manage adding and removing references, but in Vala managing such reference counts is automated if a programmer uses the language's built-in reference types rather than plain pointers.

Using functionality from native code libraries requires writing vapi files, defining the library interfacing. Writing these interface definitions is well-documented for C libraries, especially when based on GObject, however C++ libraries are currently not yet supported. Vapi files are provided for a large portion of the GNOME platform, including GTK+.

Vala was conceived by Jürg Billeter and was implemented by him and Raffaele Sandrini, finishing a self-hosting compiler in May 2006.

Code example

A simple "Hello, World!" program:

void main () {
  print ("Hello World\n");
}

A more complex version, showing some of Vala's object-oriented features:

class Sample : Object {
  void greeting () {
    stdout.printf ("Hello World\n");
  }
 
  static void main (string[] args) {
    var sample = new Sample ();
    sample.greeting();
  }
}

An example using GTK+ to create a GUI "Hello, World!" program:

using Gtk;
 
int main (string[] args) {
    Gtk.init (ref args);
 
    var window = new Window ();
    window.title = "Hello, World!";
    window.border_width = 10;
    window.window_position = WindowPosition.CENTER;
    window.set_default_size (350, 70);
    window.destroy.connect (Gtk.main_quit);
 
    var label = new Label ("Hello, World!");
 
    window.add (label);
    window.show_all();
 
    Gtk.main();
    return 0;
}

See also

• Genie, a programming language for the Vala compiler with a syntax closer to Python
• MonoDevelop, a programming IDE that runs on Linux, Windows and Mac OSX with support for Vala
• Shotwell, an image organiser written in Vala

External links

• Official website, on GNOME Live!
• LibGee, a collection library for vala.
• Val(a)IDE, an IDE for Vala
• Valencia, an IDE for Vala
• Vala Toys for Gedit, a plugin for Gedit that adds support of autocompletion and more, to program with Vala.
• Video of Jürg Billeter talking about Vala at the Gran Canaria Desktop Summit in the summer of 2009.
• API Documentation
• Vala tutorials project on launchpad.net, a place for people who like to share their experiments with newbie Vala developers
• List of Vala programs

Comparison with other languages

• Vala and Java
• Vala and C#
• Benchmark of Vala versus C# and C
• More Vala benchmarks