Squirrel Programming Language

By

Nandini Bhatta

CS537 Summer 2008

Contents

Introduction Features Development State Keywords & Operators Data types Functions, Class &

Class instance Variables Local & Global

variables….

Squirrel statements Function declaration Class declaration Array Constructor Groovy Vs Squirrel Syntax Comparision Examples Work in progress References

Introduction

Started in the year 2003 High level OO programming language Light weight programming language featuring higher-

order functions, classes/inheritance Powerful scripting tool that fits in the size, memory

bandwidth Real-time requirements of applications like games

It has a C-like syntax

Features

Open Source Inheritance Exception Handling Polymorphism Compiles on both 32-bit & 64-bit architectures Tail Recursion Dymanic Typing Automatic memory management

Development State

Two versions : 1.01 & 2.2.1

The current stable release is 2.2.1

It can be Compiled and run on Windows and Linux

Squirrel is known to run also on MacOS X, GameCube, PSP and XBOX

Keywords & Operators

Similar to keywords & operators in Java

Keyword examples : case, catch, class, constructor, parent, yield, while, return, resume, null default, delegate, delete, else, enum, switch, true, false, throw, try….

Operators examples : ! ,!=, ||, ==, &&, <=, => >, + +,/ , /=, *, *=, %, %=, ++, --, <-, =, &, ^………

Data types

Squirrel is a dynamically typed language so variables have no types

They refer to a value that does not have a type

Squirrel basic types include integer, float, string, null, table, array, function, generator, class, instance, Boolean

Functions, Class & Class instance

Functions similar to those in C language Classes created through class expression or class

statement. Class members are inherited from another class

object at creation time. After creation, members can be added until an

instance of the class is created.

Variables

Two types of variables in squirrel : local and global variables.

Global variables stored in tables and hence referred to as table slots

Local & Global variables…. Squirrel first checks if an identifier is local variable (function arguments) If not it checks if it is a member of the environment object (this) For example :

function testy(arg){local a=10;print(a);return arg;}

will access to local variable 'a' and prints 10.

function testy(arg){local a=10;return arg+foo;}

In this case ’foo’ is treated as ‘this.foo’

Global variables

Global variables are stored in root table

Environment object is the root table

To explicitly access global table from another scope, the slot name must be pre fixed with ‘::’

Example: Accessing global variable

To access global variable ‘foo’

function testy(arg)

{

local a=10;

return arg +::foo;

}

Squirrel statements

Squirrel program is a simple sequence of statements

Squirrel statements are similar to C statements such as assignment, function calls, program flow control structures etc.

Statements can be separated with new lines or using ‘;’

stats := stat [';'|'\n'] stats

Function declaration

Syntax:funcname := id [ '::' id]

stat:= 'function' id [ '::' id]+ '(' args ')'[ ':' '(' args ')'] stat

Example:T <- { }

function T::ciao(a,b,c)

{

return a+b-c;

}

Class declaration

To create a new class :

Syntax:memberdecl : = id '=' exp [ ';'] | '[ ' exp ']' '=' exp [ ';'] |

functionstat | 'constructor' stat:= 'class' derefexp ['extends' derefexp] '{'

[memberdecl]

'}‘

contd…

Example:

class Foo {//constructorconstructor(a){testy = ["stuff",1,2,3];}//member functionfunction PrintTesty(){foreach(i,val in testy){::print("idx = "+i+" = "+val+" \n");}}//propertytesty = null;}

Array Constructor

Syntax:

exp := ‘[’ [explist] ‘]’ Example:

a <- [ ] //creates an empty array

Arrays can be initialized with values during the construction

Example:

a <- [1,"string!",[ ],{ }] //creates an array with 4 elements

Groovy Vs Squirrel

Both are object oriented and dynamic languages.

Both can be used as a Scripting Language for the Java Platform.

Groovy syntax is similar to Java where as Squirrel syntax is similar to C.

Syntax Comparision

The following presents a side-by-side comparison of Groovy

with Squirrel:

Example 1:Print Statement:

Groovy:

println "hello world"

Squirrel:

Local a= “hello world”;

Print (a) ;

Example 2

Groovy:

def x = 1..10

x.each{println it}

Squirrel:

local a=0;

do

{

print(a+"\n");

a+=1;

} while(a>10

Example 3

Groovy:if (a>b) { assert c == a-bprintln c} else{assert c == b-aprintln c}

Squirrel:if(a>b){c= a-b;print (c);}else{c=b-a;Print (c);}

Inheritance Example

class Foo {function DoSomething() {::print("I'm the base");}};class SuperFoo extends Foo {//overridden methodfunction DoSomething() {//calls the base method::Foo.DoSomething();::print("I'm doing something");}}

Work in progress

Comparision with Groovy and Java

Exploring Squirrel with game programming

Exploring Squirrel SQL database

References

www.squirrel-lang.org/doc/squirrel2.pdf

www.wikipedia.org

www.sourceforge.net

www.experiencefestival.com/squirrel_programming_language_-_syntax