User Made Function : Passing an Array

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Dejunai

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Joined: 19th Jul 2005

Location: Mentally: Manhattan; Physically: LA -doh

Posted: 27th Jul 2005 00:28 Edited at: 27th Jul 2005 00:49

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( in DBP Trial )

True or False:
Can You pass an Array to a user function?

Cannot seem to locate a specific help file,
Detailing how ( if you can at all ).

If you can:
Could some please post a simple example...

I was trying this, I know it doesn't work...
It's just an simple example, of what I would like to expand on.

+ Code Snippet

dim myArray(5) as word
COUNT = array count(myArray(0))
print COUNT
SIZE = arraysize(myArray(0))
print SIZE
wait key : end

function arraysize(someLocalVariable)
   COUNT = array count(someLocalVariable)
   ACTUALSIZE = COUNT + 1
endfunction ACTUALSIZE

In other languages one might use a POINTER reference,
But the HELP documentation seems sketchy at best about
pointers.

As Always any help would be appreciated...

Edit :
As I just located a DLL at Matrix1 ( the ever generous IanM's page )
that addresses at least some of my issues,
I can assume that DBPro does not have the capability
to pass arrays to user functions...
Of course if this is incorrect,
I still look forward to any help.

================
-Dejunai
================

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Kevin Picone

22

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Joined: 27th Aug 2002

Location: Australia

Posted: 27th Jul 2005 01:23

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Not supported.

Kevin Picone
[url]www.underwaredesign.com[/url]
Play Nice! Play Basic (Release V1.08 Out Now)

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BatVink

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Joined: 4th Apr 2003

Location: Gods own County, UK

Posted: 27th Jul 2005 19:08

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Arrays are global, they can't be local. So although it's technically a limitation, you already have a workaround. You can access arrays anywhere.

BatVink

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Kevin Picone

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Joined: 27th Aug 2002

Location: Australia

Posted: 27th Jul 2005 23:20

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No, arrays can be global and local. However, he wants to pass an array (by pointer) into anfunction and perform an operation upon it. Which is not natively supported in DB or DBpro.

For example, in PlayBasic you can do this.

+ Code Snippet

; create two different arrays
 Dim Stuff(10)
 Dim Table(1000)

; fill the arrays with random stuff
 Fill(stuff())
 Fill(table())

; display the sums of both arrays
 Print  Sum(Stuff())
 Print  Sum(Table())

; Display the screen and wait for a key to be pressed
sync
waitkey

end


; This function will Fill _ANY_ passed array with random
; values
Function Fill(me())
   For lp=0 to getarrayelements(me(),1)
      me(lp)=rnd(100)
  next
EndFunction

; This Function will calc the sum of all the elements within
; the passed array
Function Sum(me())
   For lp=0 to getarrayelements(me(),1)
      r=r+me(lp)
  next
EndFunction r

Kevin Picone
[url]www.underwaredesign.com[/url]
Play Nice! Play Basic (Release V1.08 Out Now)

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BatVink

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Location: Gods own County, UK

Posted: 28th Jul 2005 00:42

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You can create arrays anywhere, including in a function. But it's still global

I take advantage of this by making arrays in Init() routines, thus making my include files 100% portable.

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IanM

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Joined: 11th Sep 2002

Location: In my moon base

Posted: 29th Jul 2005 20:07

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Arrays defined in functions can be local if you declare them as local:

+ Code Snippet

dim a(0)
a(0)=123

DoFunction()

print a(0)
wait key
end

function DoFunction()
   local dim a(0)
   a(0)=321
endfunction

If you remove the 'local' command, you'll see that things go back to being global, and the dim in the function becomes the standard 'resize array' type command.

*** Coming soon - Network Plug-in - Check my site for info ***
For free Plug-ins and source code http://www.matrix1.demon.co.uk

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Xolatron old

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Joined: 25th Jan 2004

Location: The Star Forge Language: DBpro

Posted: 30th Jul 2005 00:53

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Note, however, that you cannot create a global array inside of a function, and you must use a subruotine.

-Xol

Ion Extension Pack: 50 fncs
IonRay IDE

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BatVink

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Location: Gods own County, UK

Posted: 30th Jul 2005 01:34 Edited at: 30th Jul 2005 01:36

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You can create a global array inside a function, that's the whole point. If you look at IanM's code, you have to force DB Pro to make the array local. If you don't, it automatically becomes global.

Try this:

+ Code Snippet

	
	loadArray()
	print str$(Myarray(1))
	wait key
	
	
	function loadarray()
		dim MyArray(1) as integer
		MyArray(1) = 5
	endfunction

I always wondered why local was provided. Now it makes sense. This seems to be the only reason it's there, all other variables work based on where they are decalred.

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Xolatron old

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Location: The Star Forge Language: DBpro

Posted: 30th Jul 2005 21:36

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BatVink,
Go look at the bug reports section - I have code that won't work declaring a global array in a function, but it was rejected because arrays aren't supposed to be able to be made global in a function.

-Xol

Ion Extension Pack: 50 fncs
IonRay IDE

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IanM

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Location: In my moon base

Posted: 31st Jul 2005 15:06

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That's not what I said, or meant when I rejected your post. I said that the array name wasn't available outside the function.

An array can be declared as global within a function, and from that point will exist, but only within the function.

To make it plain:
WHERE the array is defined, determines the availability of the array name (or it's scope)
HOW the array is defined, determines where the array is stored (or it's lifetime)

So, an array declared outside of a function is available everywhere. An array declared within a function is available within the function.

An array declared as local will be created on the program stack. An array declared as global (as they are by default) will be stored in the 'static' variable area.

Once you get scope and lifetime straight, you'll understand how it works.

*** Coming soon - Network Plug-in - Check my site for info ***
For free Plug-ins and source code http://www.matrix1.demon.co.uk

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