Functions - Accepting Optional Arguments By Ref

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Arabia

(Posted 2013) [#1]

I know you can have optional arguments, i.e.

Function PrintSomething(a, b = "aaa")
EndFunction

so that b is assigned 'aaa' if no argument is passed, but is it possible to have optional arguments passed by reference?

So for the following function, can I call it by using

GetPixelColor (100,100) and have the function just return the pixel color or call it using GetPixelColor (100,100,a,r,g,b) to get the color back in it's alpha, r, g & b values?

Function GetPixelColor:Int(x:Int, y:Int, a: Int Var, r: Int Var, g: Int Var, b: Int Var)
	' Code sources:
	' http://blitzbasic.com/Community/posts.php?topic=79641#894234
	' http://www.blitzbasic.com/Community/posts.php?topic=56368#626910
	Local col:Int
	Local mypix:TPixmap=GrabPixmap(x,y,1,1)
	
	col = ReadPixel(mypix,0,0)
	a = ( col & $ff000000)
        r = ( col & $ff0000 ) Shr 16
        g = ( col & $ff00 ) Shr 8
        b = ( col & $ff )
	Return ReadPixel(mypix,0,0)
EndFunction

Yasha

(Posted 2013) [#2]

If you don't pass anything in that slot, what would the default be a reference to? There would be no safe way to use it.

TomToad

(Posted 2013) [#3]

You can pass a type with all the fields you need instead. Default to Null to make it optional

SuperStrict
Type TColor
	Field a:Int
	Field r:Int
	Field g:Int
	Field b:Int
End Type

Function GetPixelColor:Int(x:Int, y:Int, Color:TColor = Null)
	' Code sources:
	' http://blitzbasic.com/Community/posts.php?topic=79641#894234
	' http://www.blitzbasic.com/Community/posts.php?topic=56368#626910
	Local col:Int
	Local mypix:TPixmap=GrabPixmap(x,y,1,1)
	
	col = ReadPixel(mypix,0,0)
	If Color
		Color.a = ( col & $ff000000) Shr 24
        Color.r = ( col & $ff0000 ) Shr 16
        Color.g = ( col & $ff00 ) Shr 8
        Color.b = ( col & $ff )
	End If
	Return ReadPixel(mypix,0,0)
EndFunction

Graphics 640,480
SetColor 100,200,255
Plot 10,10

Print GetPixelColor(10,10)
Local Color:TColor = New TColor

GetPixelColor(10,10,Color)
Print Color.a+" "+Color.r+" "+Color.g+" "+Color.b

Arabia

(Posted 2013) [#4]

If you don't pass anything in that slot, what would the default be a reference to? There would be no safe way to use it.

Well having a default is just the way of making an argument optional, unless there is another way I'm missing. I want the code to either just return an INT specifying the color of the pixel or return an INT as well as the color breakdown into alpha, r, g & b if needed.

If I can do it with types is fine, the other way is to just write another function which converts a color INT into the Alpha, r, g & b values I guess.