Variable number of parameters for a function?

Blitz3D Forums/Blitz3D Beginners Area/Variable number of parameters for a function?

Wrath_of_Zeus

(Posted 2003) [#1]

Is it possible with blitz 3d to have a variable number of parameters for my function. I thought that I saw somewhere some instructions for it, but I can't find it now.

Gabriel

(Posted 2003) [#2]

Yes, you can make a parameter optional by specifying a default value for it.

Eg: Function MyFunction(a,b=5)

soja	(Posted 2003) [#3]

Kind of.

Basically, in your function definition, you can give some variable default parameters, like this:

Function PrintLines(Message$, howmany% = 1)
...

Notice the " = 1" assignment in the function definition. This means that if you call the function without specifying a second parameter, it will use the value 1 as the second parameter. If you do specify it, it will be whatever you sent. Here's a working code example:

PrintLines("Hello")
PrintLines("Echo", 5)

Function PrintLines(Message$, howmany% = 1)
	For i% = 1 To Abs(howmany)
		Print Message
	Next
End Function

So, as you can see, it's kind of a "variable" number of parameters, though it's not truly, since all parameters are specified one way or another, just not necessarily by you.

Note that if you have a function with default parameters, every parameter after the first default parameter must also have a default parameter. That is to say, this will not work:

Function PrintLines(Message$="", howmany%) ; <--- WON'T WORK
...

Dig it?

Wrath_of_Zeus

(Posted 2003) [#4]

I was thinking more along the lines of:

Function LoadSomeBitmaps(a, ...)

where ... is any number of bitmaps. Not so much making a parameter optional, but making it possible to have an unlimited number.

Warren

(Posted 2003) [#5]

No, I don't think that's possible.

soja	(Posted 2003) [#6]

Yeah, you can do it in other languages, but not Blitz. Of course there are all kinds of ways to pass in a variable amount of items into a function, they just can't be separate parameters. You could, say, put them into an array, and just keep loading bitmaps until the array value is 0 or something. But that might be just as hard as what you're probably doing now (calling the function multiple times, probably).

Wrath_of_Zeus

(Posted 2003) [#7]

Thanks folks. Guess I'll find another solution.

Gauge

(Posted 2003) [#8]

well no you can't do it that way, but you could do:

type bitmaplist
field a.bitmap
end type

type bitmap
field bitmapfile$
end type

dim bitmaplist(1)
b (0).bitmaplist=new bitmaplist

b (0)\ a = new bitmap
b (0)\a\bitmapfile$="World"
b (0)\ a = new bitmap
b (0)\a\bitmapfile$="grass"

Loadbitmaps b

Function Loadbitmaps(b.bitmaplist)
For each b(0)\a\ bitmap
filex=b(0)\a\bitmapfile$
file=b(0)\a\bitmapfile$+".dat"
filex=Loadimage(file)
next
end function

note- not sure if i got everythign right here, but i don't have time to test it but it should work, just figure out how to run types within types, and you can use 1 identifier. I dimmed the array with the (0) just in case, but its not neccesary. Good luck, maybe someone knows how to do this better then i do.

LostCargo

(Posted 2003) [#9]

thats prolly the best bet. but if you want to do something super dynamic, like using variants, you could always use a string or an array, and parse/use each array item

function DOWORK(myarray [])
where each item in myarray is a value of a different type

to add a twist you could make the first item in the array how the function should handle it

function dowork(myarray[])
select myarray(1)
case "DELETE PLAYER"
delete myarray(2)
case "loadplayer"
playertype = new playertype
playertype\name = myarray(2)
playertype\height = myarray(3)
playertype\weight = myarray(4)

end function