Squirrel (programming language)

Squirrel

Paradigm(s)	Multi-paradigm: scripting, imperative, functional, object-oriented
Appeared in	2003
Designed by	Alberto Demichelis
Stable release	3.0.1 (September 8, 2011 (2011-09-08))
Typing discipline	Dynamic
Influenced by	Lua, Python, C++, JavaScript
Influenced	MiniD
OS	Cross-platform
License	MIT license
Usual filename extensions	.nut
Website	squirrel-lang.org

Squirrel is a high level imperative, object-oriented programming language, designed to be a light-weight scripting language that fits in the size, memory bandwidth, and real-time requirements of applications like video games. MirthKit, a simple toolkit for making and distributing open source, cross-platform 2D games, uses Squirrel for its platform. It is used extensively by Code::Blocks for scripting and was also used in Final Fantasy Crystal Chronicles: My Life as a King It is also used in Left 4 Dead 2 and Portal 2 for scripted events.

Language features

• Dynamic typing
• Delegation
• Classes, inheritance
• Higher order functions
• Generators
• Cooperative threads (coroutines)
• Tail recursion
• Exception handling
• Automatic memory management (mainly reference counting with backup garbage collector)
• Weak references
• Both compiler and virtual machine fit together in about 7k lines of C++ code
• Optional 16-bit character strings

Syntax

Squirrel uses a C-like syntax.

Factorial in Squirrel:

  function factorial(x)
  {
    if (x == 0) {
      return 1;
    }
    else {
      return x * factorial(x-1);
    }
  }

Random numbers using generators:

  function gen_random(max) {
    local last=42
    local IM = 139968;
    local IA = 3877;
    local IC = 29573;
    for(;;) {  //loops forever
      yield (max * (last = (last * IA + IC) % IM) / IM);
    }
  }
 
  local randtor = gen_random(100);
 
  for(local i = 0; i < 10; i += 1)
     print(">"+resume randtor+"\n");

Classes and inheritance:

  class BaseVector {
    constructor(...)
    {
      if(vargv.len() >= 3) {
        x = vargv[0];
        y = vargv[1];
        z = vargv[2];
      }
    }
    x = 0;
    y = 0;
    z = 0;
  }
 
  class Vector3 extends BaseVector {
    function _add(other)
    {
      if(other instanceof ::Vector3)
        return ::Vector3(x+other.x,y+other.y,z+other.z);
      else
        throw "wrong parameter";
    }
    function Print()
    {
      ::print(x+","+y+","+z+"\n");
    }
  }
 
  local v0 = Vector3(1,2,3)
  local v1 = Vector3(11,12,13)
  local v2 = v0 + v1;
  v2.Print();

History

The language was made public in 2003 under the zlib/libpng license. In November 2010, the license was changed to MIT license to enable the project to be hosted on Google Code. It is developed and maintained by Alberto Demichelis.

See also

• Lua
• Python
• Ruby

External links

• Squirrel Home Page
• SquirrelWiki
• MirthKit Home Page
• L4D2 Vscripts