while: Difference between revisions

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m (Text replacement - "\|seealso= *\[\[([^ ]+)\]\], \[\[([^ ]+)\]\]" to "|seealso= $1 $2")
(add note about while having no suspension)
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|descr= Repeats [[Code]] while the given condition is [[true]]. A part of [[while]]-[[do]] construct.
|descr= Repeats [[Code]] while the given condition is [[true]]. A part of [[while]]-[[do]] construct.
 
{{Feature | Important | A while loop doesn't have any suspension, meaning that if used in [[Scheduler#Scheduled_Environment|scheduled environment]] without any suspension ([[sleep]] or [[uiSleep]]) the code will run multiple times per frame and consumes the 3 ms per frame scheduler execution limit. This should be avoided if not intended. See Example 3.}}
|s1= [[while]] condition
|s1= [[while]] condition


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};
};
} [[forEach]] [[units]] [[group]] unitname;</code>
} [[forEach]] [[units]] [[group]] unitname;</code>
 
|x3=<sqf>
//warning! while loop without suspension executes multiple times per frame!!!
private _counter = 0;
private _endTime = diag_tickTime + 5;
private _frameNo = diag_frameNo;
while {diag_tickTime < _endTime} do {
    _counter = _counter + 1;
};
hint format ["Average Execution: %1 times per frame", _counter / (diag_frameNo - _frameNo)];
//with suspension
private _counter = 0;
private _endTime = diag_tickTime + 5;
private _frameNo = diag_frameNo;
while {diag_tickTime < _endTime} do {
    _counter = _counter + 1;
    uiSleep 0.001; //waits at least 1 frame
};
hint format ["Average Execution: %1 times per frame", _counter / (diag_frameNo - _frameNo)];
</sqf>
|seealso= [[Control Structures]] [[waitUntil]] [[for]] [[do]]
|seealso= [[Control Structures]] [[waitUntil]] [[for]] [[do]]
}}
}}

Revision as of 19:23, 24 March 2022

Hover & click on the images for description

Description

Description:
Repeats Code while the given condition is true. A part of while-do construct.
A while loop doesn't have any suspension, meaning that if used in scheduled environment without any suspension (sleep or uiSleep) the code will run multiple times per frame and consumes the 3 ms per frame scheduler execution limit. This should be avoided if not intended. See Example 3.
Groups:
Program Flow

Syntax

Syntax:
while condition
Parameters:
condition: Code
Return Value:
While Type

Examples

Example 1:
while {a < b} do {a = a + 1};
Example 2:
A practical example: Repair all members of a group to such a level that they are able to stand up: { if (alive _x) then { while { not canStand _x } do { _x setDamage (damage _x - 0.01); }; }; } forEach units group unitname;
Example 3:
//warning! while loop without suspension executes multiple times per frame!!! private _counter = 0; private _endTime = diag_tickTime + 5; private _frameNo = diag_frameNo; while {diag_tickTime < _endTime} do { _counter = _counter + 1; }; hint format ["Average Execution: %1 times per frame", _counter / (diag_frameNo - _frameNo)]; //with suspension private _counter = 0; private _endTime = diag_tickTime + 5; private _frameNo = diag_frameNo; while {diag_tickTime < _endTime} do { _counter = _counter + 1; uiSleep 0.001; //waits at least 1 frame }; hint format ["Average Execution: %1 times per frame", _counter / (diag_frameNo - _frameNo)];

Additional Information

See also:
Control Structures waitUntil for do

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
Kronzky - c
Posted on May 14, 2008 - 08:40 (UTC)
The boolean code that is used to evaluate the while condition can be preceded by code that executes a regular command. while {_a =_a + 1; _a < 10} do {...}
Killzone Kid - c
Posted on Aug 30, 2014 - 08:12 (UTC)
In non-scheduled environment, while do loop is limited to 10,000 iterations, after which it exits even if condition is still true. In scheduled environment no such limit exists.