PreProcessor Commands

The parser allows you to use macros in configs. Macros are a bit similar to functions in programming and allow you to use a single definition many times in the config, without having to duplicate the whole definition again and again. It also gives you a centralized place to correct errors in this definition. This page mainly refer to OFP, some example don't work on ARMA and ARMA 2.
(In ArmA 3) preprocessor commands are case-sensitive!

Parsing

• Config.cpp - parsed when PBO is binarized.
  • localize cannot be used in macros, as it would hardcode string of current language instead of creating reference.
• Description.ext - parsed when mission is loaded or previewed in missions list.
• SQF script - parsed when preprocessFile, preprocessFileLineNumbers or execVM is used.

Macros

Comments

A comment is a line in your code that is not actually processed by the game engine. They are used to make your code more readable. The preprocessor removes all comments from the file, before it is processed. Therefore, any comments written in your code, will never actually be "seen" by the engine. They are for humans only.

There are two types of comments: single line comments and multi line comments.

//this is a single line comment
mycode = something; //only this part of the line is commented out
/* this
is a multi line
comment */

#define

Using the #define instruction you can define a keyword and assign a definition to it. An example:

  #define true 1

The above means that whenever you use true in your config, the parser will replace this with the value 1.

Arguments

You can add arguments to your more complex macros, by including them between brackets after the keyword:

  #define CAR(NAME) displayName = NAME;

If you now use CAR("Mini"), this will be replaced with displayName = "Mini";. Multiple arguments can also be used:

  #define BLASTOFF(UNIT,RATE) UNIT setVelocity [0,0,RATE];

Passing arrays with more than one element [el1,el2,...] as arguments into macros as well as any argument containing comas "some, sentence", will need a small workaround:

 #define HINTARG(ARG) hint ("Passed argument: " + str ARG)

Incorrect usage:

 HINTARG([1,2,3,4,5,6,7,8,9,0]); //ERROR, wouldn't even compile

Correct usage:

 #define array1 [1,2,3,4,5,6,7,8,9,0] 
 HINTARG(array1); //SUCCESS

Replacing parts of words

By default you can only replace whole words by arguments. If you need to replace only part of a word, you can use the ## instruction. This is necessary when either the start or the end of the argument connects to another character that is not a ; (semi-colon) or   (space).

  class NAME##_Button_Slider: RscText \
  { \
     model = \OFP2\Structures\Various\##FOLDER##\##FOLDER; \

You can also use the single # to convert an argument to a string.

  statement = (this animate [#SEL, 0]); \

Multi-line

For longer definitions, you can stretch the macro across multiple lines. Each line, save the last one, ends with a \ character:

  #define DRAWBUTTON(NAME)\
     __EXEC(idcNav = idcNav + 4) \
  ...

NOTE: The backslash is the last character in the line, there cannot be a space after it, for example.

#undef

Undefine (delete) a macro previously set by the use of #define.

#undef NAME

#ifdef

You can use a simple if-then construction to for example check whether a certain set of definitions has already been made:

#ifdef NAME
  ...text that will be used if NAME is defined...
#endif

IFDEFs cannot be nested, as the preprocessor will generate an error if the outer definition doesn't exist.

#ifndef

Same as #ifdef, but checks for absence of definiton instead.

#ifndef NAME
  ...text that will be used if NAME isn't defined...
#endif

#else

#ifndef NAME
  ...text that will be used if NAME isn't defined...
#else
  ...text that will be used if NAME is defined...
#endif

#endif

This ends a conditional block as shown in the descriptions of #ifdef and #ifndef above.

#include

Copies the code from a target file and pastes it where #include directive is.

#include "file.hpp"

Brackets are equal to quotation marks.

#include <file.txt>

Source directory is:

• for any file without starting the include path with \ - the file's current directory
• When starting with \ - the internal filesystem root (see [PBOPREFIX]) or the Game's working directory (only with -filePatching enabled)

To move to parent directory use '..' (two dots) (Supported in Arma 3 since v1.49.131707):

#include "..\file.sqf"

You can also write path starting from drive (only with -filePatching enabled):

#include "D:\file.txt"

Also you can write path from PBOs with [PBOPREFIX]:

#include"\x\myAddon\file.txt" // x here is the pboprefix's id;

or without it (keep in mind that if the PBO's file name will be changed all #include where you used it will need to be changed too)

#include"\myAddon\file.txt" // Arma 3\myMod\addons\myAddon.pbo\file.txt;

Preprocessor does not support computed includes (macro for file name).

#define path "codestrip.txt"
#include path

This code will cause an error. Macros will be explained later.

#

'#' (single hash) operator wraps the text with quotation marks.

#define STRINGIFY(s) #s;
#define FOO 123
test1 = STRINGIFY(123); //test1 = "123";
test2 = STRINGIFY(FOO); //test2 = "123";

##

'##' (double hash) operator concatenates what's before the ## with what's after it.

#define GLUE(g1,g2) g1##g2
#define FOO 123
#define BAR 456
test1 = GLUE(123,456); //test1 = 123456;
test2 = GLUE(FOO,BAR); //test2 = 123456;

__EXEC

This config parser macro allows you to assign values to internal variables. These variables can be used to create complex macros with counters for example.

  __EXEC(cat = 5 + 1; lev = 0)

This macro terminates at the first ) it encounters, so the following will not be possible:

  __EXEC(string1 = "if ((_this select 0) == 22) then {true}")

When you evaluate string1 it returns "if ((_this select 0" and can cause unexpected results. The variables that receive expression result inside __EXEC are available in parsingNamespace:

_cat = parsingNamespace getVariable "cat"; //6
_lev = parsingNamespace getVariable "lev"; //0

NOTE: Config parser macros are not suitable for sqf/sqs scripts but can be used in configs, including description.ext.

__EVAL

With this config parser macro you can evaluate expressions, including previously assigned internal variables. Unlike with __EXEC, __EVAL supports multiple parentheses

  w = __EVAL(safezoneW - (5 * ((1 / (getResolution select 2)) * 1.25 * 4)));

NOTE: Config parser macros are not suitable for sqf/sqs scripts but can be used in configs, including description.ext. Both global and local variables set in __EXEC are available in __EVAL.

__LINE__

This keyword gets replaced with the line number in the file where it is found. For example, if __LINE__ is found on the 10th line of a file, the word __LINE__ will be replaced with the number 10.

__FILE__

This keyword gets replaced with the CURRENT file being processed.

External links

• http://ofp-faguss.com/files/ofp_preprocessor_explained.pdf