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Squirrel (programming language)

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Squirrel is a high level imperative, object-oriented programming language, designed to be a lightweight 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.cite-ref-2[2] It is used extensively by Code::Blocks for scripting and was also used in Final Fantasy Crystal Chronicles: My Life as a King.cite-ref-gamasutra-3-0[3]cite-ref-4[4] It is also used in Left 4 Dead 2, Portal 2 and Thimbleweed Park for scripted events and in NewDark, an unofficial Thief 2: The Metal Age engine update, to facilitate additional, simplified means of scripting mission events, aside of the regular C scripting.cite-ref-5[5]

Contents

• Language features

• Syntax

• Applications

• Applications using Squirrel

• Games using Squirrel

• History

• See also

• References

• External links

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 support for UCS-2 wide strings

Syntax

Squirrel uses a C-like syntax, albeit inspired by that of Lua as well.

Factorial in Squirrel

local function factorial(x) // Getting function which is factorial, then getting value which is x

{

if (x <= 1) { // if x is less than 1

return 1; // then the code will just return 1

}

else { // if that doesn't work

return x * factorial(x-1); // then the code will return x times factorial(x-1)

}

Generators

function not_a_random_number_generator(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 = not_a_random_number_generator(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();

Applications

Applications using Squirrel

• Code::Blocks, integrated development environment

• Enduro/X, cluster application server

• Electric Imp, an end-to-end IoT platformcite-ref-electric-imp-6-0[6]

Games using Squirrel

• Alien Swarmcite-ref-vscript-7-0[7]

• Antinomy of Common Flowerscite-ref-8[8]

• Apex Legends

• Battle Brothers

• Contagioncite-ref-vscript-7-1[7]

• Counter Strike: Global Offensivecite-ref-vscript-7-2[7]

• CRSED: F.O.A.D.

• Final Fantasy Crystal Chronicles: My Life as a Kingcite-ref-gamasutra-3-1[3]

• Gothic Online,cite-ref-9[9] a mod for Gothic II

• GTA IV's IV-MPcite-ref-10[10]

• Left 4 Dead 2cite-ref-vscript-7-3[7]

• Liberty Unleashedcite-ref-11[11]

• Mafia II's M2-Multiplayercite-ref-12[12]

• Melty Blood: Type Luminacite-ref-13[13]

• Nuclear Dawncite-ref-vscript-7-4[7]

• OpenTTDcite-ref-14[14]

• Portal 2cite-ref-vscript-7-5[7]

• Shadow Warrior

• Simutranscite-ref-15[15]

• Sonic Unleashed (PS2/Wii)cite-ref-vgresource-16-0[16]

• SuperTux

• Team Fortress 2cite-ref-vscript-7-6[7]

• Thimbleweed Parkcite-ref-17[17]

• Thief II (unofficial NewDark engine update)cite-ref-ttlg-18-0[18]

• Titanfallcite-ref-vscript-7-7[7]

• Vice City Multiplayer,cite-ref-19[19] a mod for Grand Theft Auto: Vice Citycite-ref-20[20]

• Under Night In-Birthcite-ref-21[21]

• War Thunder

• Zero no Tsukaima - Maigo no Period to Ikusen no Symphony (PS2)

• Zero no Tsukaima - Muma ga Tsumugu Yokaze no Nocturne (PS2)

• Zero no Tsukaima - Shou-akuma to Harukaze no Concerto (PS2)

History

The language was made public in 2003 under the zlib/libpng license.cite-ref-22[22] In November 2010, the license was changed to the MIT license to enable the project to be hosted on Google Code.cite-ref-23[23]cite-ref-24[24] It is developed and maintained by Alberto Demichelis.