Arma 2 Forward Compatibility

[sbsmac]

Although this is perfectly valid in arma:
Code Sample

MyGlobalVariable = nil;

I don't think that is a declaration - very much the reverse! Note the following is not based on any knowledge of ArmA internals but from experience with analoguous interpreted systems. It's possible BIS have a different implementation but I would be surprised if so...

The best way to think of 'definedness' of variables is to consider that they live in a database(1) where entries consist of name/value pairs.

When you create a new variable with "myVar=1" you are actually creating an entry in the database where the 'name' field is set to "myVar" and the 'value' field is set to 1. (There is probably a 'type' field in ArmA but this is irrelevant to this discussion.)

When you subsequently run "myVar=2", the existing entry is updated with a new value field.

Assigning a 'value' of 'nil' to a variable can be used to remove an entry from the database. Note that 'nil' is not really a value at all, it is simply a convenient syntax. So you should really think of "myVar=nil" as "Undefine myVar". Similarly the 'isNil' command is best thought of as a test to see if an entry for that variable exists in the database.

Another point, in contrast to 'nil', which means that a variable doesn't even exist, 'null' is a valid value and just means that the thing to which the variable refers doesn't exist.

So, I would expect the following behaviour...

//Define a variable
myVar=1;
//Now delete it again
myVar=nil;

//Testing for existence can be done with 'isnil'
if (isNil "myVar") then {
  hint "no variable called myVar exists";}

//This should throw an error in Arma2 since we've just
//deleted the variable
hint format ["myvar is %1",myVar];

The 'private' command is interesting since it implies that it is creating uninitialised variables. When I get some time on my gaming PC I'll have a quick check to see if those variables are created with a null value.

(1) Of course, 'database' is a loose term here - it is usually a table/linked-list/hash/binary-tree or other simple structure.

[ACF]

There was some suggestion somewhere that SQF format scripting is the way forward.
Will ArmA 2 support SQS and SQF, or SQF only?

[SNKMAN]

I belive ArmA 2 will support like ArmA 1 bouth .sqs and .sqf there is no reason why BIS should drop .sqs

[rrores]

Hi

_func = 
{
   _return = nil;
   _return
};

_var = [] call _func;

if !(isNil "_var") then
{
 ...................
};

this gives error?

[Sickboy]

Sqf is imho indeed the way forward.
It's structure is imho a lot better compared to sqs and the possibilities to precompile and call or spawn later is a huge plus also.
I also believe in unification and generalization of code, so imho all should be coded in 1 language and not multiple. As SQF has it's advantages over SQS I drop SQS as a whole personally.

I believe sqs will still be supported in ArmA2, but why would you use it is my question

[benreeper]

SQS makes for ugly, hard to follow, compromised code. SQF is also easier to use and more closely resembles what you may be used to if you used other languages. To me, it feels as if my Arma projects run smoother that my OFP ones.
--Ben

[SNKMAN]

Hi

_func =
{
_return = nil;
_return
};

_var = [] call _func;

if !(isNil "_var") then
{
...................
};

this gives error?

Well i understood it this way:

You have to initialize every variable bevore first use so:

WORKS:

_number = 0;
if (number == 0) then {hint "Zero"};

DIDN'T WORK:
Becouse the variable has to be initialized BEVORE then {};

if (alive player) then {_number = 0};
if (number == 0) then {hint "Zero"};

But you still can use "isNil" becouse isNil do only check if the variable exist, and if not then it will be created.

[rrores]

DIDN'T WORK:
Becouse the variable has to be initialized BEVORE then {};

if (alive player) then {_number = 0};
if (number == 0) then {hint "Zero"};

(thanks to respond)

that does not work either in arma1.

[Sickboy]

Basicly it just comes down to this:
You must first initialize (set variable Type) a variable before you use it:


Good:
_var1 = 0; player globalChat format ["Test: %1", _var1];

Bad:
player globalChat format ["Test: %1", _var1];

This code in ArmA would make player globalChat sth like "Test: SCALAR BOOL ARRAY STRING ....."
The same code in ArmA2 will report an error, because _var1 was not initialized before.

Good

if (isNil "GlobalVar") then { GlobalVar = "" };
player globalChat format ["%1", GlobalVar];

Bad

player globalChat format ["%1", GlobalVar];

This code in ArmA would make player globalChat sth like "SCALAR BOOL ARRAY STRING ....."
The same code in ArmA2 will report an error, because GlobalVar was not initialized before

Hi

_func =
{
_return = nil;
_return
};

_var = [] call _func;

if !(isNil "_var") then
{
...................
};

this gives error?

I think this will work just fine. _var = nil destroys a variable if it existed, but doesnt create it if it didn't before.
isNil "_var" should be a valid test

[Baddo]

DIDN'T WORK:
Becouse the variable has to be initialized BEVORE then {};

if (alive player) then {_number = 0};
if (number == 0) then {hint "Zero"};

(thanks to respond)

that does not work either in arma1.

There is a typo isn't there.

And it is intentionally done wrong (not the typo but the logic) to show you what doesn't work.