How to use #ifdef

[brutell]

While using e2, you might find that some servers have plugins, like propcore, and others do not. Unfortunately, if you script your e2 to take advantage of a plugin, then it will error on servers that do not have the plugin.

However, one may use the functionality of #ifdef to avoid that.

#ifdef allows the e2 to check if a function exists. Not what it returns, but if the function is defined at all. However, it checks IF A FUNCTION IS DEFINED (Hi, jason!), NOT THE VARIABLE IT RETURNS!

Usage is like so-

#ifdef argument:aFunction( argument )
#else
#endif

The main part is the bit after ifdef. When using ifdef, the script has to know what arguments to check. If it doesn't know, then it will check for the wrong function. One mistake that may be made is as such

#ifdef applyForce()
print( "Applyforce is defined." )
#else
print( "Applyforce isn't defined." )
#endif

However, this will never be true. applyForce requires a vector, and thus when it checks for applyForce without the vector, it doesn't find a function, and so goes to the else.

You have to provide the proper types of arguments. If the function takes a vector, you would write

#ifdef applyForce( vector )

This would return true, unlike our earlier check. The same goes for array, number, string, etc.

You may be thinking at this point, "What use would this have to me?"
Well, it would, as mentioned above, allow you to check if the server has a plugin. For example,

#ifdef entity:setPos( vector )
#else
#endif

This would allow you to check if you could teleport your entities, as opposed to applyForcing them into place, for example

#ifdef entity:setPos( vector )
Prop:setPos( AVariablePosition )
#else
Prop:applyForce( ( AVariablePosition - Prop:pos() - Prop:vel() / 2 ) * Prop:mass() )
#endif

Additionally, its possible to forsake the #else, but it would be kind of pointless. You could at least print a warning and selfDestruct, or something.

#ifdef notAFunction()
print( "Wow." )
#endif

Well, I really can't think of anything else, so if you can think of anything, let me know. I think there was a guide before, but I searched and couldn't find one.

[Unsmart]

Nice, and detailed tut.

/votesticky

[vexx21322]

Wow, I was just thinking about this and trying to use it, then I come to wiremod.com and you have a thread about it...

[Schilcote]

I didn't know E2 had preprocessor directives...

[Matte]

I didn't know E2 had preprocessor directives...

@name
@inputs
@outputs
@persist
@trigger
@model

[jacoby6000]

Sooo...

#ifdef holoModelAny(Number,String)
holoModelAny(N,E:model())
#else
holoModel(N,"")
#endif

Is that correct?

[Schilcote]

@name
@inputs
@outputs
@persist
@trigger
@model

No, those aren't preprocessor directives. They're settings for the chip. Preprocessor directives change the way code is compiled. Those affect the low level operations of the E2.

[Matte]

No, those aren't preprocessor directives. They're settings for the chip. Preprocessor directives change the way code is compiled. Those affect the low level operations of the E2.

Preprocessor directives are just commands that instructs the compiler, and that doesn't directly affect the code. The directives I mentioned fall under this category. If you're still disagreeing, look at some of the posts of 'The Master' (Syranide), himself. He calls them directives.

[NikoKun]

We need more tutorials on these sorts of things. I'm glad someone finally did this one, I've wondered about it for a while. Thanks!

[ktccd]

This was taught to me in a server once... It was, by far, the MOST useful anyone has ever taught me in E2. Now I can use propcore without breaking stuff! I implemented this in my spike sphere ^^.

Well:

Additionally, its possible to forsake the #else, but it would be kind of pointless. You could at least print a warning and selfDestruct, or something.

That made me lol. "I mean come on! At the very least you could blow it up!"