An Introduction to Squirrel: Difference between revisions

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Save the file then go back in game and press your bind, you should see your text in console!
Save the file then go back in game and press your bind, you should see your text in console!


== [https://sigwiki.potato.tf/index.php?title=An_Introduction_to_Squirrel Variables] ==
Every program in any programming language is comprised of a set of instructions called statements which manipulate data to produce a desired result. Programs store data into regions of memory as objects. Objects which we give an identifier (name) in our programs are called variables. You can think of statements as analogous to sentences in the language we speak to each other, each requires a specific set of items to be considered valid, and each is ended with a specific character. Sentences are mostly ended with periods, and statements always end with a semicolon.
Identifiers have a few considerations to keep in mind:
* '''They are case-sensitive, wep is not the same as WEP'''
* '''The first character must be alphabetical (a-z) or an underscore, afterwards they can have any combination of (a-z), (0-9), or underscores'''
* '''Underscores are the only special character allowed, nothing else'''
'''Valid Identifiers:'''
* INDEX
* _weapon
* weapon_sequence
* player123
'''Invalid Identifiers:'''
* starting-index
* 1_ring_to_rule_them_all
* BOLD&BRASH
* $IMBATMAN
In addition, identifiers cannot be the same name as a keyword, which are special identifiers reserved by the language for its use in the syntax. We'll go over most of these throughout the guide, so don't worry about memorizing them just yet.
{| class="wikitable" style="width:75%; margin:auto; text-align:center font-weight:bold; font-size:125%"
|+Keywords
|base
|break
|case
|catch
|class
|clone
|-
|continue
|const
|default
|delete
|else
|enum
|-
|extends
|for
|foreach
|function
|if
|in
|-
|local
|null
|resume
|return
|switch
|this
|-
|throw
|try
|typeof
|while
|yield
|constructor
|-
|instanceof
|true
|false
|static
|__LINE__
|__FILE__
|-
|rawcall
|
|
|
|
|
|}
<div style="margin-top: 50px;">To define a variable with x as it's identifier, we use the <code>'''local'''</code> keyword:</div>
<syntaxhighlight lang="c" line="1" start="1" style="font-weight:bold;">
local x;
</syntaxhighlight>
We created our variable in this statement but we haven't given it a value, so currently the value for x is <code>'''null'''</code>, which is a special value representing the lack of a value. To give our variable an actual value we have two options; we can set it at the time of definition (which is called initialization), or we can assign it a value with the assignment (<code>'''='''</code>) operator in a separate statement, or both!
<syntaxhighlight lang="c" line="1" start="1" style="font-weight:bold;>
local x;
local y = 10;
x = 5;
y = 0;
</syntaxhighlight>
Here we define x and initialize y to 10, and then set x to 5 and y to 0 afterwards.
== [https://sigwiki.potato.tf/index.php?title=An_Introduction_to_Squirrel Comments] ==
A comment is a human readable note which was inserted by a programmer to denote the what, how, or why behind code. Comments are ignored by the compiler and only serve to make the code easier to understand or use for programmers. Comments come in two flavors: single line and multi line comments. Single line comments go until they hit a new line character (\n). Multi line comments have a start and end token, anything between them is commented out.
To insert a single line comment, prefix it with <code>'''//'''</code> or <code>'''#'''</code>.
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
// I'm a comment that takes the whole line
local darth_variable = 404 # I'm an inline comment
</syntaxhighlight>
To insert a multi line comment, use <code>'''/*'''</code> to start and <code>'''*/'''</code> to end.
<syntaxhighlight lang="c" line="1" start="1" style="font-weight:bold;>
/*I
      am
          a
      multi
  line
comment
*/
local foo = 2;
</syntaxhighlight>
You can "nest" single line comments, but you can't do this with multi line comments
<syntaxhighlight lang="c" line="1" start="1" style="font-weight:bold;>
//////////////////////// okay
/* // okay */
/* /* not okay */ */
</syntaxhighlight>
The compiler will end the multi line comment at the first end token (*/) it sees, so the second one is outside of any comments and results in a compile error.
== [https://sigwiki.potato.tf/index.php?title=An_Introduction_to_Squirrel Data Types] ==
Data stored in variables can have a number of different types which determines what type of object it is and what you can do with it. Below is the full list of data types in Squirrel, however we will only go over the primitive ones in this section. The other data types will receive their own sections later in the guide.
'''Data Types:'''
* Null
* Integer
* Bool
* Float
* String
* Table
* Array
* Function
* Generator
* Class
* Instance
* Thread
* Userdata
To get a variable's data type as a string (see below on strings), you can use the <code>'''typeof'''</code> operator.
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local t = typeof 5; // "integer"
</syntaxhighlight>
<hr>
<span style="font-size:120%">'''Null'''</span>
Has one value: <code>'''null'''</code>, it represents the non-existence or lack of a value.
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local x; // null
local y = 5;
// ...
y = null;
</syntaxhighlight>
<hr>
<span style="font-size:120%">'''Integer'''</span>
Represents a 32 bit whole number, meaning it can store any value from -2,147,483,648 to 2,147,483,647. You can specify the integer base as [https://en.wikipedia.org/wiki/Hexadecimal hexadecimal] by prefixing with <code>'''0x'''</code> or [https://en.wikipedia.org/wiki/Octal octal] with <code>'''0'''</code>. You can also specify [https://www.asciitable.com/ ASCII] char codes between single quotes '''<code>'</code>''' which will be stored as their integer value.
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local x = 12345;    // Decimal
local y = 0xFFFFFF; // Hexadecimal begins with 0x
local z = 050;      // Octal begins with 0
local c = 'a';      // Char code stored as 97
</syntaxhighlight>
These are all integer '''literals''', which are hard coded pieces of data within a program for a specific data type. Other types have literals as well which you'll see in the examples below.
<hr>
<span style="font-size:120%">'''Bool'''</span>
Has two values: <code>'''true'''</code> and  <code>'''false'''</code>.
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local is_stuck    = false;
local should_round = true;
</syntaxhighlight>
<hr>
<span style="font-size:120%">'''Float'''</span>
Represents a 32 bit floating point number, meaning it can store any decimal value from 1.18e-38 to 3.4e38. Due to how floating point numbers are stored in memory, they have a limited amount of accuracy for a certain number of significant digits, for a 32 bit float it's usually around 6 or 7 digits. Any additional digits for the float value may result in rounding errors and precision loss. Keep this in mind when you're working with floats.
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local float1 = 1.23456;  // 1.23456 (Regular float literal)
local float2 = 1.2e34;  // 1.2e+34  (Scientific notation float literal)
// Precision loss
local float3 = 1.234567; // 1.23457
local float4 = 1234.567; // 1234.57
local float5 = 123456.7; // 123457
local float6 = 12345678999.0; // 1.23457e+10
</syntaxhighlight>
You cannot have a leading floating point for float literals, they must start with at least one digit.
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
// Invalid
local float1 = .123;
local float2 = .12E5;
// Valid
local float3 = 0.123;
local float4 = 0.12E5;
</syntaxhighlight>
<hr>
<span style="font-size:120%">'''String'''</span>
Strings are a sequence of characters with any length between quotation marks <code>"</code>. Strings are immutable, meaning they cannot be modified and you must create a new string if you need to change the old one. Regular strings must begin and end on the same line, they cannot contain any new line characters (\n).
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
// Strings ...
local str1 = "'''@!(&(*@!%&!(%!%(%&FJSGADFJKL@fadjsh141a=-"; // String
local str2 = "123"; // String with number characters, not an integer
local str3 = "a";  // String
local str4 = "";    // Empty string
// ... compared to char codes
local int1 = 'a';  // NOT a string
local int2 = '';    // Compile error
local int3 = ''';  // Compile error
local int4 = '\'';  // 39, Valid char code for ' (explained below)
// Need to make a new string if we want to modify
local name = "bar";
name = "barber";
</syntaxhighlight>
Strings (and char literals) may contain [https://en.cppreference.com/w/c/language/escape escape sequences], which special are characters that denote that something special should happen. Even though they have multiple characters in their definition, they count as one character when actually in use.
Here are the ones you're most likely to use:
* <code>'''\t'''</code> - Display a tab
* <code>'''\n'''</code> - Move to a new line
* <code>'''\\'''</code> - Insert \ char
* <code>'''\"'''</code> - Insert " char
* <code>'''\''''</code> - Insert ' char
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local text  = "Hello there! Please enter your class:\t";    // Tab
local text2 = "What do you mean you don't \"have one\"?\n"; // " char and new line
</syntaxhighlight>
There may come a time when you need a string that does not interpret escape sequences or that can span multiple lines, which is where verbatim strings come in handy. Verbatim strings begin with <code>'''@"'''</code> and end with a regular quote <code>'''"'''</code>.
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local mystring = @"eenie
meenie
minie
moe";
</syntaxhighlight>
You may also need to add quote characters within the verbatim string, to do so you double up each quotation <code>'''""'''</code>. The double quote will be replaced with a single quote by the compiler.
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local mystring = @"eenie
""meenie""
minie
moe";
</syntaxhighlight>
== [https://sigwiki.potato.tf/index.php?title=An_Introduction_to_Squirrel Operators] ==
Now that you know how to create data and store it into variables, we can now go over how to modify and operate on that data. Operators are used for this purpose, they take one or more operands and produce a result value. Operators which take one operand are called unary operators, two operands are binary operators, and three are ternary operators.
This section is quite long so don't worry about memorizing every single operator, just browse through and become familiar with the various types of operators and their uses, you'll have plenty of examples throughout the rest of the guide to work with.
<hr>
<span style="font-size:120%">'''Arithmetic'''</span>
'''Unary Operators'''
{| class="wikitable" style="width:100%; margin:auto; text-align:center font-weight:bold; font-size:110%"
|+
!Operator
!Symbol
!Form
!Operation
|- style="text-align:center"
|Unary minus
| -
| -x
|Negation of x
|}
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local x = 50;
x = -x; // -50
</syntaxhighlight>
'''Binary Operators'''
{| class="wikitable" style="width:100%; margin:auto; text-align:center font-weight:bold; font-size:110%"
|+
!Operator
!Symbol
!Form
!Operation
|- style="text-align:center"
|Addition
| +
| x + y
|x plus y
|- style="text-align:center"
|Subtraction
| -
| x - y
|x minus y
|- style="text-align:center"
|Multiplication
| *
| x * y
|x multiplied by y
|- style="text-align:center"
|Division
| /
| x / y
|x divided by y
|- style="text-align:center"
|Remainder
| %
| x % y
|the remainder from: x divided by y
|}
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local v = 100 + 100; // 200
local w = 0 - 2;    // -2
local x = 5.5 * 100; // 550.0
local y = 20 / 2;    // 10
local z = 23 % 2;    // 1
</syntaxhighlight>
The addition operators <code>'''+'''</code> and <code>'''+='''</code> are also able to handle string operands. If one operand is a string, Squirrel will try to convert the other operand to a string as well.
This same type conversion happens between floats and integers for any arithmetic operator (not just addition). If one operand is a float and the other an integer, the resulting value will be a float.
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local str1 = "Hello,";
local str2 = " World!";
str1 += str2; // Hello World!
// See next section for +=
local float = 10 - 7.0 // 3.0
</syntaxhighlight>
<hr>
<span style="font-size:120%">'''Assignment'''</span>
{| class="wikitable" style="width:100%; margin:auto; text-align:center font-weight:bold; font-size:110%"
|+
!Operator
!Symbol
!Form
!Operation
|- style="text-align:center"
|Assignment
| =
| x = y
|assign value y to variable x
|- style="text-align:center"
|Addition Assignment
| +=
| x += y
|assign x + y to variable x
|- style="text-align:center"
|Subtraction Assignment
| -=
| x -= y
|assign x - y to variable x
|- style="text-align:center"
|Multiplication Assignment
| *=
| x *= y
|assign x * y to variable x
|- style="text-align:center"
|Division Assignment
| /=
| x /= y
|assign x / y to variable x
|- style="text-align:center"
|Remainder Assignment
| %=
| x %= y
|assign x % y to variable x
|- style="text-align:center"
|}
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local x = 100;
x += 5;  // equivalent to: x = x + 5
x -= 5;  // 100
x *= 100; // 10,000
x /= 2;  // 5,000
x %= 2;  // 0
</syntaxhighlight>
<hr>
<span style="font-size:120%">'''Increment/Decrement'''</span>
{| class="wikitable" style="width:100%; margin:auto; text-align:center font-weight:bold; font-size:110%"
|+
!Operator
!Symbol
!Form
!Operation
|- style="text-align:center"
|Pre-increment
| ++
| ++x
|increment x by 1, then return x
|- style="text-align:center"
|Post-increment
| ++
| x++
|copy x, increment variable x by 1, then return the copy
|- style="text-align:center"
|Pre-decrement
| --
| --x
|decrement x by 1, then return x
|- style="text-align:center"
|Post-decrement
| --
| x--
|copy x, decrement variable x by 1, then return the copy
|}
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local x = 1;
local y;
y = x++; // y = 1, it got the value of x and then x got incremented, x = 2
y = ++x; // y = 3, x got incremented and then y got x's value
</syntaxhighlight>
<hr>
<span style="font-size:120%">'''Relational'''</span>
{| class="wikitable" style="width:100%; margin:auto; text-align:center font-weight:bold; font-size:110%"
|+
!Operator
!Symbol
!Form
!Operation
|- style="text-align:center"
|Equality
| ==
| x == y
|true if x equals y, false otherwise
|- style="text-align:center"
|Inequality
| !=
| x != y
|true if x does not equal y, false otherwise
|- style="text-align:center"
|Less than
| <
| x < y
|true if x is less than y, false otherwise
|- style="text-align:center"
|Greater than
| >
| x > y
|true if x is greater than y, false otherwise
|- style="text-align:center"
|Less than or equal to
| <=
| x <= y
|true if x is less than or equal to y, false otherwise
|- style="text-align:center"
|Greater than or equal to
| >=
| x >= y
|true if x is greater than or equal to y, false otherwise
|}
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local x = 5;
local y = 5;
local z;
z = x == y; // true
z = x != y; // false
z = x > y;  // false
z = x >= y; // true
z = x < y;  // false
z = x <= y; // true
</syntaxhighlight>
<span style="font-size:120%">'''Logical'''</span>
{| class="wikitable" style="width:100%; margin:auto; text-align:center font-weight:bold; font-size:110%"
|+
!Operator
!Symbol
!Form
!Operation
|- style="text-align:center"
|Logical NOT
| !
| !x
|true if x evaluates to false, otherwise false
|- style="text-align:center"
|Logical AND
| &&
| x && y
|true if both operands evaluate to true, otherwise false
|- style="text-align:center"
|Logical OR
| <nowiki>||</nowiki>
| x <nowiki>||</nowiki> y
|true if either operand evaluates to true, otherwise false
|}
For most purposes the above definitions for AND & OR are sufficient, however Squirrel does not simply return boolean true or false for these operators, rather it returns a specific operand passed to the operator based on the result.
Logical AND, if either operand evaluates to false, will return the '''first''' operand that evaluates to false. Otherwise if both evaluate true the operator will return the '''last''' operand.
Logical OR will return the first operand that evaluates to true, if none do, it will return the '''last''' operand.
Certain values evaluate to false, these are: <code>'''false, null, 0, 0.0'''</code>. Everything else evaluates to true.
<syntaxhighlight lang="c#" line="1" start="1" style="font-weight:bold;>
local v = 0 && 1;        // 0
local w = null || "bark"; // "bark"
local x = "" || true;    // ""
local y = !0;            // true
local z = 5 && "0"        // "0"
</syntaxhighlight>
<span style="font-size:120%">'''Bitwise'''</span>
&, |, ^, ~, <<, >>, >>>
<span style="font-size:120%">'''Other Operators'''</span>
in, instanceof, typeof, comma, ternary
<span style="font-size:120%">'''Operator Precedence'''</span>
-, ~, !, typeof , ++, -- highest
/, *, % …
+, -
<<, >>, >>>
<, <=, >, >=, instanceof
==, !=, <=>
&
^
&&, in
+=, =, -=, /=, *=, %= …
, (comma operator) lowest
IntegerLiteral        ::=  [1-9][0-9]* | '0x' [0-9A-Fa-f]+ | ''' [.]+ ''' | 0[0-7]+
FloatLiteral          ::=  [0-9]+ '.' [0-9]+
FloatLiteral          ::=  [0-9]+ '.' 'e'|'E' '+'|'-' [0-9]+
StringLiteral        ::=  '"'[.]* '"'
VerbatimStringLiteral ::=  '@''"'[.]* '"'




Revision as of 23:10, 26 October 2023

Overview

This is a relatively brief beginner's guide to the Squirrel language (v3.2) aimed at people with no programming experience interested in trying their hand at VScript. The only prerequisite knowledge you are expected to have is basic knowledge of the Source engine. While in theory this guide is not technically specific to any Source game in particular, it is for version 3.2 which is unique as TF2's version of Squirrel. L4D2, Portal, and other Source games run on older versions, so in practice this guide is directed at TF2 players. If you're following this guide for another Source game that's perfectly fine, just be aware that some features may not function, or they might behave differently in your game's version of Squirrel. You'll also need to store your .nut files in the appropriate place of whatever game you're using, rather than the tf/scripts/vscripts folder.

If you already have experience with C-like languages or programming in general I would recommend you visit the Squirrel Reference Manual for a more expedient learning experience more aimed at developers.


Getting Started

While it's possible to compile the Squirrel source code into binaries with which you can test your code outside of a Source game, simply launching a game and executing your script is much simpler and allows us to test game specific code, so that's what we'll do for the duration of the guide. For guides on VScript itself, the VDC has an excellent collection:

To get set up, navigate to your tf/ directory and add a scripts/vscripts folder if it doesn't already exist and create a file with any name with the extension .nut. You should have a location something like this: C:\Program Files (x86)\Steam\steamapps\common\Team Fortress 2\tf\scripts\vscripts\testing.nut

Go ahead and launch your favorite Source game which supports VScript and load into any map on a local server, then bind any key to "script_execute testing". For example: bind 5 "script_execute testing"

Tab out of your game, open your .nut file and type: 

printl("Hello World!");

Save the file then go back in game and press your bind, you should see your text in console!


Expressions

Intro to Functions

Intro to Objects

Scope

Control Flow

if/else if/else for foreach while do while switch break continue

Exceptions

try catch throw

Enums

Arrays

Tables

Functions

Generators

Delegation

Weak References

Classes

Inheritance

Metamethods

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