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<code style="display: inline; margin: 0px; padding: 2px;">Status Quo Function</code> is the successor of <code style="display: inline; margin: 0px; padding: 2px;">[[SQS_syntax|Status Quo Script]]</code> which is deprecated since [[Armed Assault]].
SQF was first introduced in [[Operation_Flashpoint:_Resistance_Introduction|Operation Flashpoint: Resistance]].


== Language Structure ==
The SQF Language is fairly simple in how it is built.
In fact: there are barely any actual language structures at all.
The functionality is provided via so called ''operators'' (or more commonly known [[Category:Scripting_Commands_Arma_3|scripting commands]]).
Those operators are one of the following types: Nular, Unary or Binary.
=== Comments ===
A comment is additional text that gets ignored when a script is parsed.
They exists for the purpose of you, the coder, being able to add additional info to your code so that if somebody else (including your future you) is looking into the code can understand what you did there.
In SQF, there are two kind of comments:
{{codecomment|//In-line comment that ends on new line}}
{{codecomment|/* Block Comment that can span above multiple lines and ends on the following character combination: */}}
A comment can occur anywhere but inside a string.
For example, the following would be valid:
1 + {{codecomment|/* Some random coment in an expression. */}} 1
It should be mentioned, that there is a [[comment]] unary operator that should not be used as it will actually be executed (thus taking time to execute) but does nothing besides consuming a string.
There is no benefit in using it and the reason it exists is soely for Backward Compatibility.
=== Nular Operators ===
A Nular Operator is more or less a computed variable. Each time accessed, it will return the current state of something.
It is tempting to think of a Nular Operator as nothing more but a magic [[Variables|Global Variable]], but it is important to differentiate!
Consider following example in a mission with eg. 5 units:
{{codecomment|//Put the result of [[allUnits]] into a [[Variables|variable]].}}
_unitsArray = [[allUnits]];
{{codecomment|//Display the current array size using [[systemChat]].}}
[[systemChat]] [[str]] [[count]] _unitsArray;
{{codecomment|//Create a new unit in the player group.}}
[[group]] [[player]] [[createUnit]] ["B_RangeMaster_F", [[position]] [[player]], [], 0, "FORM"];
{{codecomment|//Output the array size again}}
[[systemChat]] [[str]] [[count]] _unitsArray;
{{codecomment|//Output the size of [[allUnits]]}}
[[systemChat]] [[str]] [[count]] [[allUnits]];
Now, what would the output of this look like?
System: 5
System: 5
System: 6
As you can see, <code style="display: inline; margin: 0px; padding: 2px;">_unitsArray</code> was not automatically updated. If [[allUnits]] was a [[Variables|Global Variable]], our private variable should have had reflected the change.
The reason for this is because [[allUnits]] and other Nular commands just return the current state of something and do not return a reference to eg. an [[Array]] containing all units.
It is generated each time, which is why some of theese commands are more expensive to run then ''just'' using a variable.
=== Unary Operators ===
The Unary Operators are operators that expect an argument on their right side (<code style="display: inline; margin: 0px; padding: 2px;">unary &lt;argument&gt;</code>). They always will take the first argument that occurs.
A common mistake would be the following:
{{codecomment|//Create some array containing three arrays.}}
_arr = [[1, 2, 3, 4, 5], [1, 2, 3, 4], [1, 2]];
{{codecomment|//Wrongly use the [[select]] command to get the count of the third array.}}
[[count]] _arr [[select]] 2; {{codecomment|//Error}}
Now, what went wrong?
Let's put some brackets in the right places to make the mistake understandible:
([[count]] _arr) [[select]] 2; {{codecomment|//Error}}
Due to the nature of Unary operators, count instantly consumes our [[Variables|variable]] ''_arr'' and returns the number ''3''.
The ''3'' then is passed to [[select]] which does not knows what to do with a number as left argument and thus errors out.
To do it correctly, one would have to put the <code style="display: inline; margin: 0px; padding: 2px;">_arr select 2</code> in brackets.
The correct code thus would be:
{{codecomment|//Create some array containing three arrays.}}
_arr = [[1, 2, 3, 4, 5], [1, 2, 3, 4], [1, 2]];
{{codecomment|//Use Brackets to correctly get count of the third array.}}
[[count]] (_arr [[select]] 2); {{codecomment|//Good :)}}
=== Binary Operators ===
Binary Operators expect two arguments (<code style="display: inline; margin: 0px; padding: 2px;">&lt;1st argument&gt; binary &lt;2nd argument&gt;</code>) and are executed according to their [[#precedence|precedence]]. If their [[#precedence|precedence]] is equal, they are executed left to right.
As example, we will look into the following Expression:
{{codecomment|//Create a nested [[Array]] with 5 levels.}}
_arr = [[[[[1]]]]];
{{codecomment|//Receive the nested number with some random math expressions.}}
_arr select 0 select 1 - 1 select 15 / 3 - 5 select 0 select 10 * 10 + 4 * 0 - 100
Now, let us analyze why this is happening for the first few expressions:
# _arr is loaded
# 0 is loaded
# [[select]] is executed with the result of 1. & 2.
# 1 is loaded
# 1 is loaded
# [a_minus_b|-] is executed with the result of 4. & 5.
# [[select]] is executed with the result of 3. & 6.
# ...
If we now would put brackets at the correct spots, the expression will get more clear:
((((_arr select 0) select (1 - 1)) select ((15 / 3) - 5)) select 0) select (((10 * 10) + (4 * 0)) - 100)
As you can see the [[a_*_b|*]] and [[a_/_b|/]] are executed first which matches their [[#precedence|precedence]]. Afterwards, the [[a_plus_b|+]] and [[a_minus_b|-]] operators will get executed followed by our [[select]] commands, which are executed from the left to the right.
== <span id="precedence">Rules Of Precedence</span> ==
{|
|1 '''Lowest Precedence'''
|<code>[[a or b|<nowiki>||</nowiki>]] [[a or b|or]]</code>
|-
|2
|<code>[[and|&&]] [[and]]</code>
|-
|3
|<code>[[==]] [[!=]] [[a_greater_b|&gt;]] [[a_less_b|&lt;]] [[a_less=_b|&gt;=]] [[a_less=_b|&lt;=]] [[config_greater_greater_name|&gt;&gt;]]</code>
|-
|4
|''ALL BINARY OPERATORS''
|-
|5
|<code>[[else]]</code>
|-
|6
|<code>[[a_plus_b|+]] [[a_minus_b|-]] [[max]] [[min]]</code>
|-
|7
|<code>[[a_*_b|*]] [[a_/_b|/]] [[mod|%]] [[mod]] [[atan2]]</code>
|-
|8
|<code>[[a_^_b|^]]</code>
|-
|9
|''ALL UNARY OPERATORS''
|-
|10 '''Highest Precedence'''
|''ALL NULAR OPERATORS, VARIABLES, VALUES OR BRACED EXPRESSIONS''
|}
<!-- [[Category: Syntax]] [[Category:Scripting Topics]] -->

Latest revision as of 21:12, 18 November 2019

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