User Defined Types and Functions

Blitz3D Forums/Blitz3D Beginners Area/User Defined Types and Functions

LostCargo

(Posted 2003) [#1]

Alright. Ive been using blitzbasic for a while, but i am no pro yet. I just have two quick questiosn i hope someone can help me out with.

Am i correct in assuming that passing *ANY* variable into a function, that it is being passed byREF always?

And if so, when i try and pass in UserDefined Types it does not allow me to do so. Is there a trick to passing user defiend types into functions? or will i have to make the user defined type that holds the object/entity global?

If anyone could answer i would be really appreciative.

Beaker

(Posted 2003) [#2]

Function parameters are all passed by value. BUT, type objects are essentially pointers to the data, so they are effectively passed by reference.

To pass a type into a function:

Type thing
Field x,y
End Type

t.thing = New thing
doit(t)
Print t\x  ; should display "20"
End

Function doit(athing.thing)
athing\x = 20
End Function

LostCargo

(Posted 2003) [#3]

As always, the BlitzForums never fail to produce good help.
Thanks MasterBeaker. U rock man. Good call.

Tricky

(Posted 2003) [#4]

It's not really the way I prefer, but I guess it does work... I really prefer the direct thing like other languages support... But I found my ways to live with the miss...

Koriolis

(Posted 2003) [#5]

???
What is essentially different (apart from the super super syntax in Blitz, myInstance\myField...WTF???)
Can you be clearer?

Neo Genesis10

(Posted 2003) [#6]

When a variable is passed by reference any changes to the variable are kept when the function exits. In some small way its the same as using a global. The following psuedo (Blitz / VB hyrbid ) functions should make things clearer...

ammo = 47
ShootWeapon( ammo )
; ammo now equals 46

Function ShootWeapon( byREF ammo )
	ammo = ammo - 1	; Actually changes the value
	MakeBullet
End Function

ammo = 47
ammo = ShootWeapon( ammo )

Function ShootWeapon( byVAL ammo )
	MakeBullet
	Return ammo - 1	; Has to return the value
End Function

Hope it makes things clearer...

Koriolis

(Posted 2003) [#7]

Yes, exactly like in any other language that supports pointer and/or reference... that is almost any useable language. Thanks NeoGenesis10 but I wasn't requesting any explanation here, types are pretty straight forward to use when you already know languages like Java or C++. I was asking Tricrokra what difference he sees in this.