if: Difference between revisions

From Bohemia Interactive Community
Jump to navigation Jump to search
(add. classification)
No edit summary
 
(68 intermediate revisions by 17 users not shown)
Line 1: Line 1:
{{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 construct available in many languages. This syntax however has alternate forms in the manner of an [[Array]].
|game3= arma1
*if (condition) then {code} else {code}
|version3= 1.00
*if (condition) then [ {code},{code} ]


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} ]
|= Syntax


|p1= condition: [[Boolean]] expression, determining if the code should be executed or not (when not, another code may be executed)|= Parameter 1
|game6= tkoh
| [[If Type]] - Predicate which will execute 1st or 2nd option when used. This predicate is used in [[then]] or [[exitWith]] commands. |= Return value
|version6= 1.00
____________________________________________________________________________________________


|x1= <code>_retVal <nowiki>=</nowiki> if (1 > 0) [[then]] {"It's true"} [[else]] {"It's false"};
|game7= arma3
[[hint]] [[str]] _retVal
|version7= 0.50
</code> |=Example 1
____________________________________________________________________________________________


| [[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>


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


"if a then x, y, z"
|seealso= [[else]] [[exitWith]] [[then]] [[Control Structures]] [[Code_Optimisation#Lazy_evaluation|Lazy evaluation]]
or
}}
"if a then x; y; z"
</dd>


<dt class="note">'''[[User:Ceeeb|Ceeeb]]'''</dt>
{{Note
<dd class="note">
|user= Ceeeb
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= 20070131040800
</dd>
|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.
}}


<!-- Note Section END -->
{{Note
</dl>
|user= Galzohar
|timestamp= 20100117024000
|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
}}


<h3 style="display:none">Bottom Section</h3>
{{Note
|user= AgentRevolution
|timestamp= 20150605093500
|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
[[Category:Scripting Commands|IF]]
|user= DreadedEntity
[[Category:Scripting Commands OFP 1.96|IF]]
|timestamp= 20220519011146
[[Category:Scripting Commands ArmA|IF]]
|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
[[Category:ArmA: Control Structures|IF]]
<sqf>private _myVar = "value";
[[Category:Command Group: Program Flow|IF]]
private _condition = false;
[[Category:Scripting Commands ArmA2|{{uc:{{PAGENAME}}}}]]
_myVar = if (_condition) then { "another value" }; //perfectly valid sqf
[[Category:Scripting Commands VBS2|{{uc:{{PAGENAME}}}}]]
systemChat str (isNil "_myVar"); //returns true
//_myVar is now nil
_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 03:11, 19 May 2022

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)

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

AgentRevolution - 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