if: Difference between revisions

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m (Text replacement - "<sqf>([^↵][^<]*↵[^<]*)<\/sqf>" to "<sqf> $1 </sqf>")
 
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{{Command|= Comments
{{RV|type=command
____________________________________________________________________________________________


| ofpr |= Game name
|game1= ofp
|version1= 1.85


|1.85|= Game version
|game2= ofpe
____________________________________________________________________________________________
|version2= 1.00


| The standard if, then, else constuct available in many languages. This syntax however has alternate forms in the manner of an [[Array]], or, as a which (?) operator.
|game3= arma1
*if (condition) then {code} else {code}
|version3= 1.00
*if (condition) then [ {code},{code} ]
*? (condition) : {code} (no else alternative for the which syntax)


Result of the [[Code]] executed is returned as the result to this command (which may be [[Nothing]]}.|= Description
|game4= arma2
____________________________________________________________________________________________
|version4= 1.00


|
|game5= arma2oa
*[[Anything]] <nowiki>=</nowiki> '''if''' (condition) '''then''' {[[Code]]} '''else''' {[[Code]]}
|version5= 1.50
*[[Anything]] <nowiki>=</nowiki> '''if''' (condition)  [ {ThenCode} , {ElseCode} ]
*'''?''' (condition) : {[[Code]]}|= Syntax


|p1= condition: statement that returns a [[Boolean]] |= Parameter 1
|game6= tkoh
|p2= [[Code]]: statement(s) executed when condition true, or false |= Parameter 1
|version6= 1.00
| [[Anything]]- Dependent on {[[Code]]} executed |= Return value
____________________________________________________________________________________________


|x1= <code>if (a>b) [[then]] <nowiki>{c=0}</nowiki> [[else]] <nowiki>{c=1}</nowiki></code> |=Example 1
|game7= arma3
____________________________________________________________________________________________
|version7= 0.50


| [[else]], [[Control Structures]], [[then]] |= See also
|gr1= Program Flow


}}
|descr= This operator creates a [[If Type]] which is used in the if-construct as described [[Control_Structures#if-Statement|here]].


<h3 style="display:none">Notes</h3>
|s1= [[if]]  condition
<dl class="command_description">
<!-- Note Section BEGIN -->


<dd class="notedate">Posted on August 4, 2006 - 10:55</dd>
|p1= condition: [[Boolean]] - if it evaluates as [[true]], the [[then]] clause is executed.  Otherwise, the [[else]] clause (if present) is executed
<dt class="note">'''[[User:Hardrock|hardrock]]'''</dt><dd class="note">''Notes from before the conversion:''


Standard syntax:
|r1= [[If Type]] - predicate which will execute 1st or 2nd option when used. This predicate is used in [[then]] or [[exitWith]] commands


<nowiki>=</nowiki> if a [[then]] b
|x1= <sqf>
_retVal = if (1 > 0) then { "It's true" } else { "It's false" };
hint str _retVal;
</sqf>


Alternative syntax
|x2= <sqf>
_val = if (true) then [{ "true" }, { "false" }];
hint _val;
</sqf>


<nowiki>= ? a : b </nowiki>
|seealso= [[else]] [[exitWith]] [[then]] [[Control Structures]] [[Code_Optimisation#Lazy_evaluation|Lazy evaluation]]
}}


Compound clause syntax (multiple actions)
{{Note
|user= Ceeeb
|timestamp= 20070131040800
|text= Any _local variables you declare within the body of an [[if]]/[[then]] statement (ie between the curly braces) are local to that 'if' statement, and are destroyed at the end of the statement. If you know you want to use the variable outside the 'if' statement, make sure your declare it before the 'if' statement.
}}


"if a then x, y, z"
{{Note
or
|user= Galzohar
"if a then x; y; z"
|timestamp= 20100117024000
</dd>
|text= If the condition is nil then neither the "then" nor the "else" section get executed, but the script will proceed with no error messages.<br>
Example code:
<sqf>
systemChat "script started"; // will get executed
if (nil) then
{
systemChat "true"; // will never get executed
}
else
{
systemChat "false"; // will never get executed
};
systemChat "script ended"; // will get executed
</sqf>
|game= arma2
|version= 1.05
}}


<dt class="note">'''[[User:Ceeeb|Ceeeb]]'''</dt>
{{Note
<dd class="note">
|user= AgentRev
Any variables you declare within the body of an if/[[then]] statement (ie between the curly braces) are local to that 'if' statement, and are destroyed at the end of the statement. If you know you want to use the variable outside the 'if' statement, make sure your declare it before the 'if' statement.
|timestamp= 20150605093500
</dd>
|text= If you only need to choose between 2 raw values, it is possible to use the following trick to avoid using code blocks, as required by the if command, which results in greater atomicity and faster execution:
<sqf>_result = [falseValue, trueValue] select condition;</sqf>
The select command treats "false" as 0 and "true" as 1, therefore you can feed it a condition determining the array index of the value to be returned. Here is another example:
<sqf>_result = [1,-1] select (_this < 0); // if _this is less than 0, _result will be equal to -1, otherwise it will be 1</sqf>
}}


<!-- Note Section END -->
{{Note
</dl>
|user= DreadedEntity
 
|timestamp= 20220519011146
<h3 style="display:none">Bottom Section</h3>
|text= When using '''if''' to assign values to a variable, if you not have an [[else]] block it is treated as [[nil]] and returned, setting the variable value to [[nil]]. A3 2.08.149102
 
<sqf>
 
private _myVar = "value";
[[Category:Scripting Commands|IF]]
private _condition = false;
[[Category:Scripting Commands OFP 1.96|IF]]
_myVar = if (_condition) then { "another value" }; //perfectly valid sqf
[[Category:Scripting Commands ArmA|IF]]
systemChat str (isNil "_myVar"); //returns true
[[Category:ArmA: Control Structures|IF]]
//_myVar is now nil
[[Category:Command Group: Program Flow|IF]]
_myVar = if (_condition) then { "another value" } else { "value" };
systemChat _myVar; //returns "value"
</sqf>
This behavior can be both desirable and undesirable depending on your needs
}}

Latest revision as of 19:43, 3 September 2024

Logo A0.png1.85ofpe logo.png1.00Logo A1 black.png1.00Logo A2.png1.00A2 OA Logo.png1.50tkoh logo small.png1.00Arma 3 logo black.png0.50
Hover & click on the images for description

Description

Description:
This operator creates a If Type which is used in the if-construct as described here.
Groups:
Program Flow

Syntax

Syntax:
if condition
Parameters:
condition: Boolean - if it evaluates as true, the then clause is executed. Otherwise, the else clause (if present) is executed
Return Value:
If Type - predicate which will execute 1st or 2nd option when used. This predicate is used in then or exitWith commands

Examples

Example 1:
_retVal = if (1 > 0) then { "It's true" } else { "It's false" }; hint str _retVal;
Example 2:
_val = if (true) then [{ "true" }, { "false" }]; hint _val;

Additional Information

See also:
else exitWith then Control Structures Lazy evaluation

Notes

Report bugs on the Feedback Tracker and/or discuss them on the Arma Discord or on the Forums.
Only post proven facts here! Add Note
Ceeeb - c
Posted on Jan 31, 2007 - 04:08 (UTC)
Any _local variables you declare within the body of an if/then statement (ie between the curly braces) are local to that 'if' statement, and are destroyed at the end of the statement. If you know you want to use the variable outside the 'if' statement, make sure your declare it before the 'if' statement.
Galzohar - c
Posted on Jan 17, 2010 - 02:40 (UTC)
Logo A2.png1.05

If the condition is nil then neither the "then" nor the "else" section get executed, but the script will proceed with no error messages.
Example code:

systemChat "script started"; // will get executed if (nil) then { systemChat "true"; // will never get executed } else { systemChat "false"; // will never get executed }; systemChat "script ended"; // will get executed

AgentRev - c
Posted on Jun 05, 2015 - 09:35 (UTC)
If you only need to choose between 2 raw values, it is possible to use the following trick to avoid using code blocks, as required by the if command, which results in greater atomicity and faster execution:
_result = [falseValue, trueValue] select condition;
The select command treats "false" as 0 and "true" as 1, therefore you can feed it a condition determining the array index of the value to be returned. Here is another example:
_result = [1,-1] select (_this < 0); // if _this is less than 0, _result will be equal to -1, otherwise it will be 1
DreadedEntity - c
Posted on May 19, 2022 - 01:11 (UTC)
When using if to assign values to a variable, if you not have an else block it is treated as nil and returned, setting the variable value to nil. A3 2.08.149102
private _myVar = "value"; private _condition = false; _myVar = if (_condition) then { "another value" }; //perfectly valid sqf systemChat str (isNil "_myVar"); //returns true //_myVar is now nil _myVar = if (_condition) then { "another value" } else { "value" }; systemChat _myVar; //returns "value"
This behavior can be both desirable and undesirable depending on your needs
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