Function

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Revision as of 19:54, 20 December 2006 by CrashDome (talk | contribs) (Armed Assault: Elaborated on suspending functions and the effect of the calling script)
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Introduction

Functions were first introduced into an OFP: Resistance patch.

Usage

A function is much like a regular scripting command except that you can use functions to create something like a custom command. A function is simply a chunk of code that does something, the function can then return a value to the point which 'called' that function or it can simply return Nothing.

Functions differ from scripts in that they halt all other game engine processes until the function has completed its instructions. This means functions run faster than scripts, and the result of functions is immediate and unambiguous. It can also mean that if a function takes too long to run it will have an adverse effect on game play - large functions or CPU intensive functions can cause the game to seize up until it completes. When creating a functions you want the function to be short and sweet to achieve the best results.

Functions have a limitation of 10,000 loops before they are forced to exit by the game engine in order to maintain some level of stability.

Functions can only be executed via the call command and as a result must use SQF syntax.

Operation Flashpoint

Functions are first compiled via preprocessFile command or loaded dynamically via the loadFile command. They are then executed via the call command. Functions in OFP cannot be paused and must finish execution before the game will continue.

Armed Assault

Starting with Armed Assault, functions can wait suspended (like SQS or SQF-style scripts), using sleep or waitUntil. However, the calling script remains suspended also (unlike SQS or SQF-style scripts).

Function Execution Diagram.jpg

Examples

Example 1 (max.sqf) In this example the function returns maximum of first and second argument.

comment "Return maximum of first and second argument"
private {"_a","_b"};
_a = _this select 0;
_b = _this select 1;
if (_a>_b) then {_a} else {_b}


Example 2 (infantrySafe.sqf) In this example the function returns no value and switches all units to safe mode.

comment "Switch all infantry units to safe mode";
{
 if (vehicle _x == _x) then
 {
  _x setBehaviour "safe"
 }
} forEach _this


Example 3 (inline function) An inline-function can be created in any script:

FNC_sayhello = {hint format["hello %1",_this];}

This function can then be called (in other scripts, functions, unit's init lines, trigger activation fields, etc.) via:

name player call FNC_sayhello

Notice that there are no brackets around the functions arguments which precede the call command.
In case the function doesn't require any arguments you can use empty brackets instead [] call FNC_helloall.

See also

call