Squirrel
| Squirrel Version | Release Date[1] | Games |
|---|---|---|
| 2.2.3 | 2009-06-30 | |
| 3.0.4 | 2012-11-10 | |
| 3.2 | 2022-02-10 |
Squirrel is a programming language similar to Lua, but uses a C like syntax. In Source, Squirrel is used as one of the scripting languages in the VScript scripting system. The official Squirrel documentation can be found here.
in operator should be at the <, <=, >, >= level. Squirrel heavily uses an
associative array data structure called a table. Both the keys and values of a table can contain almost any kind of variable type. The scripting environment consists of nested tables, and when a script is executed its variables and functions are added as table slots.
printl("Hello World"); // statements can end with both a semicolon...
printl("Hello World") // ...or a newline character
Squirrel's syntax is similar to C/C++/Java etc... but the language has a more dynamic nature like Python/Lua etc.
Statements can be separated with both a new line or
(or with the keywords
or
if inside a switch/case statement), both symbols are not required if the statement is followed by
.
File format
Variables
Squirrel has mainly two kinds of variables: table slots and
variables.
This doesn't have to do with types; Like in Python, any variable can be of any data type at any time and there are no type declarations. Since the execution scope is always a table, any variables declared outside functions will always be table slots.
- Table slots have to be declared using the
operator. These are to be used for values that should persist when a function ends. Once a slot exists, it can be reassigned with both the
or the
operator. The former will throw an exception if the slot does not exist and should be preferred if a reassignment is expected (and not a slot creation).
- Local variables can be declared using the
keyword. Each of these is only accessible in the scope it was defined in, namely its surrounding curly brackets. They are to be used temporarily or as helpers that can be discarded later on. A typical example is a
loop with an index variable:
.
- Global variables are simply table slots in the root table (
). They can be declared using the
scoping operator and accessed with or without it.
- Constants are declared with the
keyword and are intended for values that will never change at runtime, such as
Pi or a string representing a file path. Since constants are a compile-time feature, their value is computed compile-time and thus can only be an integer, float or string. Attempting to assign a new value to a constant yields a compile-time error
; It can be imagined that Squirrel replaces each occurrence of the constant's identifier in the code with its current value, hence the error message. Current, because the same constant can be defined multiple times in code but with different values (with the
keyword). During runtime,
returns a table with all constants that have been found during compiling; If more code is compiled, that very table is used to resolve constants. The constants table and its values behave normally and don't have any protection that constants usually have.
Note:
and
variables are declared with the
operator. Using
for those yields a compile time error.
a <- 5 // creates a table slot in this table
b <- "A text string" // creates a table slot in this table
::x <- 10 // creates a table slot in the root table
local i = 0 // initializes a temporary variable
const E = 2.71828 // creates a new constant
b = "New string" // modifies the existing table slot
x = 11 // modifies the existing table slot
|
The
operator can be used to test whether a table slot exists. One could also do:
. The following code is assumed to be executed after the above, i.e. in the same environment.
"a" in this // true
"x" in this // false, unless we're in the root table
"i" in this // false, local variables aren't table slots
"E" in this // false, unless we're in the constants table
delete a // deletes a table slot
"a" in this // false, no longer exists
|
Data Types
Squirrel is a dynamically typed language. Any variable can be assigned a value of any type.
The built-in function
returns the type of an input value as a string in lower case, e.g.
.
| Type | Description |
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This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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The integers This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
In code, a number becomes a float by adding a decimal point. The notations This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
There are no constants for +infinity, -infinity and NaN, but This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
When converted to a string using This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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An immutable string. They behave like C strings, and support escape sequences ( This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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Null data type with the only value This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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Boolean data type that can be This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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Associative array. |
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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Mutable C style array. |
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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Second order functions are supported, so functions can be assigned as values to variables. |
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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Object oriented class. Implementation similar to tables. |
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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Object instances of classes. Script handles generated by the game also identify as instances. |
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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A function whose execution can be suspended and resumed. |
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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Opaque data used by the game. |
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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A coroutine instance, works similarly to a generator but has it's own execution stack. |
This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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A weak reference will be set to This article has been marked as a candidate for speedy deletion because it has been deprecated for the following reason: "The Code template no longer has presets, meaning there is no need for this template."
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Bool
Squirrel considers
,
(type Integer) and
(type Float) as
, any other value is considered
. This allows you for example to null-check variables using
.
if (false) { /* ... */ } // not executed
if (null) { /* ... */ } // not executed
if (0) { /* ... */ } // not executed
if (0.0) { /* ... */ } // not executed
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Tables
Tables are associative arrays, meaning that they contain a collection of key-value pairs, called slots. A table can be indexed into using the key, returning the associated value. The keys and values can be of any data type (except
for the key), including other tables, allowing the creation of more complex data structures. Tables are defined using curly brackets. Inside a table definition slots can be defined using the
pattern. Outside of the definition, new slots can be added to existing tables using the
pattern. Using the
operator to index a key only works when the key is a string or numerical literal. Array style indexing
can be used to index any kind of key.
// Table definition. Commas between key-value pairs are
// optional if whitespace is present. However, they are
// required if the next key is inside square brackets.
myTable <-
{
a = 3 // key: "a", value: 3
b = 7, // key: "b", value: 7
[6] = "six" // key: 6 , value: "six"
func = function() // key: "func"
{
return a + b
}
nestedTable = // key: "nestedTable"
{
z = "a string"
}
}
// alternatively:
myTable <- {}
myTable["a"] <- 3 // string keys can be indexed...
myTable.b <- 7 // ...in two ways
myTable[6] <- "six" // numbers must be indexed like this
myTable.func <- function() { return a + b }
myTable.nestedTable <- { z = "a string" }
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// Iterating through a table:
// 'key' and 'value' are arbitrary
foreach (key, value in myTable)
{
printl(key + ": " + value)
}
// Prints (order might vary!):
// a: 3
// func: (function : 0x00000000005AD280)
// b: 4
// 6: six
// nestedTable: (table : 0x000000000069D130)
// The 'in' operator checks for keys, not values:
printl("a" in myTable) // prints "true"
printl( 3 in myTable) // prints "false"
printl(myTable.func()) // prints 10 (a+b)
// Every table has a built-in length function:
printl(myTable.len()) // prints 5
delete myTable.a // removes the pair a=3
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Arrays
Arrays are sequences of objects that are numerically indexed starting from 0. Syntactically they function similarly to C arrays, but unlike C arrays, they are mutable and values can be inserted and removed using a set of built in functions.
Arrays are defined using square brackets.
// Array definition. Commas between values
// are optional if whitespace is present.
myArray <-
[
7, // key: 0, value: 7
"text", // key: 1, value: "text"
null // key: 2, value: null
]
// alternatively:
myArray = [4, "text", null]
// alternatively:
myArray <- []
myArray.append(7)
myArray.append("text")
myArray.append(null)
// alternatively:
myArray <- array(3)
myArray[0] = 7
myArray[1] = "text"
myArray[2] = null
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// Iterating through an array:
// 'i' and 'value' are arbitrary
foreach (i, value in myArray)
{
printl(i + ": " + value)
}
// alternatively:
for (local i = 0; i < myArray.len(); i++)
{
printl(i + ": " + myArray[i])
}
// Prints:
// 0: 7
// 1: more text
// 2: null
// The 'in' operator checks indices, not values:
printl( 2 in myArray) // prints "true"
printl("text" in myArray) // prints "false"
printl(myArray.len()) // prints 3
myArray.remove(0) // removes the element at index 0
// and rearranges all other indices
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Functions
Functions in Squirrel work similarly to their C counterparts. Second order functions are supported, so functions can be directly manipulated like other values, including it being possible to store them in variables and table slots. Default parameter values and variable numbers of parameters are also supported.
For more details, see the Squirrel API about functions.
It is common practice to begin with a capital letter when naming functions.
// Function definition. Note that functions
// are just like variables that consist of
// a name and a value where the value
// contains the key word 'function'.
Greet <- function()
{
printl("Hello!")
}
someTable <-
{
Greet = function()
{
printl("Hello!")
}
}
// Functions can be local:
local GreetLocal = function()
{
printl("Hello!")
}
// Call these functions using "()".
// All of these print "Hello!":
Greet()
someTable.Greet()
GreetLocal()
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// There is also a second syntax for convenience.
// All of this is equivalent to the code on the
// left. By the way, the brackets '{' and '}'
// are optional if there is just one statement.
function Greet()
{
printl("Hello!")
}
someTable <-
{
function Greet()
{
printl("Hello!")
}
}
local function GreetLocal()
{
printl("Hello!")
}
// Shorter: local function GreetLocal() printl("Hello!")
// All of these print "Hello!":
Greet()
someTable.Greet()
GreetLocal()
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When a function is called, it can be made so that it can or must receive input values that determine the function's side effects and/or its return value.
- Multiple parameters must be comma delimited in the function definition:
For function calls, whitespace is sufficient instead of commas:
- All parameters with no default value must be ordered first.
- To avoid exceptions, it is often a good idea to check if a parameter is not
.
- As parameters are not restricted to a type, the
function can be used to handle different types differently.
// normal parameter
function Greet(name)
{
printl("Hello, " + name + "!")
}
Greet() // exception
Greet("Gabe") // prints "Hello, Gabe!"
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// parameter with default value
function Greet(name = "Gordon")
{
printl("Hello, " + name + "!")
}
Greet() // prints "Hello, Gordon!"
Greet("Gabe") // prints "Hello, Gabe!"
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A function can have a variable number of arguments by specifying
as last parameter. In the function body, the variable
will be available and behaves like a normal array.
// Squirrel 3.x
varArgFunction <- function(delimiter, ...)
{
foreach (i, arg in vargv)
print(i + delimiter + arg + "\n")
}
varArgFunction(" : ", 4, null, "string")
// prints:
// 0 : 4
// 1 : null
// 2 : string
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// Squirrel 2.x
varArgFunction <- function(delimiter, ...)
{
for (local i = 0, i < vargc; i++)
print(i + delimiter + vargv[i] + "\n")
}
varArgFunction(" : ", 4, null, "string")
// prints:
// 0 : 4
// 1 : null
// 2 : string
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A function is ended with the optional
statement, where it is also possible to return a value. You can imagine a return value as being 'inserted' into where the function was called. If no return value is specified within the function, it returns the value as
.
function IsEven(n)
{
if (n % 2 == 0)
return true
else
return false
}
// alternatively:
IsEven <- function(n) return n % 2 == 0
if (IsEven(42)) // (42 % 2 == 0) == true
{
printl("42 is even!")
}
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Since Squirrel 3.x, there are lambda expressions which are used as a more convenient way to define a function that just returns a single expression. These are especially useful when a function is needed as a parameter for a different function such as
or
.
local func = @(a,b) a - b // == function(a,b) { return a - b }
printl( func(17,9) ) // prints 8
local arr = [1,5,4,6,2,3]
arr.sort(func)
// arr == [1,2,3,4,5,6]
arr = arr.map( @(x) x * x ) // == function(x) { return x * x }
// arr == [1,4,9,16,25,36]
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Generators
A generator is a function where the key word
appears; It suspends the execution of that generator function and can return some expression to the function that had resumed it. Some generator
can be resumed with the expression
; The value of this
expression is what was
ed when the function has been suspended the last time. The
value of a generator does not matter. Generators can be used in
statements, such that no
statement must be typed. In this scenario, generators can be advantageous because they can calculate their next value just in time, whereas iterating over a precalculated array or table can be disadvantageous if the iteration ends before the end of that array or table is reached due to unnecessary calculations. Also, generators can yield a potentially infinite number of values whereas the number of values that arrays and tables can hold is finite.
function PowersOfTwo()
{
for (local n = 1; true; n *= 2)
yield n
}
local x = 100
// Set x to the smallest power of 2
// that is larger than or equal to x:
foreach (i,pow in PowersOfTwo())
{
if (pow >= x)
{
x = pow
break
}
}
Classes
The following is just an example of some basic class syntax. For details, see Squirrel API about classes.
class Weapon
{
static prefix = "weapon_" // static variables are read-only!
// For instance-individual variables it's best to declare
// them with anything and overwrite them on construction.
name = null
primMax = null
secMax = null
// Containers and instances are not copied per instance, just
// the reference. count[0] is the same for all of instances.
count = [0]
constructor(name, prim, sec)
{
this.name = prefix + name
this.primMax = prim
this.secMax = sec
count[0]++
}
function GetEntities()
{
local list = []
local wep = null
while ( wep = Entities.FindByClassname(wep, name) )
{
list.append(wep)
}
return list
}
function _tostring() return this.name
// ... more useful functions ...
}
awp <- Weapon("awp", 10, 30)
ak47 <- Weapon("ak47", 30, 90)
// can access class variables and functions
// with awp.primMax, awp.GetEntities(), etc.
Files
With the Source VScript system, scripts are stored in the
directory. Squirrel scripts use the
file extension, and the
extension for ICE encrypted files. Common to all Squirrel using games, scripts can be associated to a game entity as an entity script that is executed then the entity spawns, and has access to the script handle of its entity through the
variable. Specific games can also have other methods of executing scripts.
Script files can also be executed from the Developer Console using the script_execute command. Lines of code can even be executed in-line with the script command.
See also
External links
Squirrel (programming language)- Squirrel Official Website
- Notepad++ syntax highlighting
- Squirrel Binary for Windows
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