Empty arrays

[Digisoul]

Hello,

I wrote a script where I was using empty Arrays like below:

Func SomeFunc()
Local $Array[]
;do something with array
EndFunc

and the script was working perfectly, but now AutoIt is giving error:

>Running AU3Check (3.3.11.2)  from:C:\Program Files (x86)\AutoIt3
+>21:05:40 AU3Check ended.rc:0
>Running:(3.3.11.2):C:\Program Files (x86)\AutoIt3\autoit3.exe "C:\Users\Digi\Desktop\test.au3"    
--> Press Ctrl+Alt+F5 to Restart or Ctrl+Break to Stop
"C:\Users\Digi\Desktop\test.au3" (7) : ==> Variable subscript badly formatted.:
Global $aTable[]
Global $aTable[^ ERROR
->21:05:40 AutoIt3.exe ended.rc:1
>Exit code: 1    Time: 0.310 

I want to confirm that, Empty Arrays are removed from new AutoIt version ?

[Melba23]

Digisoul,

No AutoIt still has empty arrays, but if you do not assign values to the array when you create it you need to explicitly define the size of the dimensions:

#include <Array.au3>
#include <MsgBoxConstants.au3>
#include <AutoItConstants.au3>

Global $aArray[]= [1] ; Implicit sizing
MsgBox($MB_SYSTEMMODAL, "Size", "Array has " & UBound($aArray, $UBOUND_ROWS) & " items")

_ArrayDelete($aArray, 0)
MsgBox($MB_SYSTEMMODAL, "Size", "Array has " & UBound($aArray, $UBOUND_ROWS) & " items")

_ArrayAdd($aArray, 1)
MsgBox($MB_SYSTEMMODAL, "Size", "Array has " & UBound($aArray, $UBOUND_ROWS) & " items")

Global $aArray[0] ; Explicit sizing
MsgBox($MB_SYSTEMMODAL, "Size", "Array has " & UBound($aArray, $UBOUND_ROWS) & " items")

All clear?

M23

[water]

This still works

Global $aArray[0]
ConsoleWrite(UBound($aArray, 1) & @LF)

[Digisoul]

Digisoul,

No AutoIt still has empty arrays, but if you do not assign values to the array when you create it you need to explicitly define the size of the dimensions:

#include <Array.au3>
#include <MsgBoxConstants.au3>
#include <AutoItConstants.au3>

Global $aArray[]= [1] ; Implicit sizing
MsgBox($MB_SYSTEMMODAL, "Size", "Array has " & UBound($aArray, $UBOUND_ROWS) & " items")

_ArrayDelete($aArray, 0)
MsgBox($MB_SYSTEMMODAL, "Size", "Array has " & UBound($aArray, $UBOUND_ROWS) & " items")

_ArrayAdd($aArray, 1)
MsgBox($MB_SYSTEMMODAL, "Size", "Array has " & UBound($aArray, $UBOUND_ROWS) & " items")

Global $aArray[0] ; Explicit sizing
MsgBox($MB_SYSTEMMODAL, "Size", "Array has " & UBound($aArray, $UBOUND_ROWS) & " items")

All clear?

M23

 

 

 

This still works

Global $aArray[0]
ConsoleWrite(UBound($aArray, 1) & @LF)

Thanks for your reply, I am not exactly sure but I remember that in one of the beta I was able to operate like:

Global $array[]
For $x = 0 to 99
 $array[$x] = $x
Next

But I got the correct syntax and operation of array.

[Melba23]

Digisoul,

That was an undocumented feature that was tested in some of the Beta releases but has since been removed. It might or might not return in the future but for now it is not valid and the correct syntax is as I showed above.

M23

[FaridAgl]

What about this one:

Global $aArray = []
ConsoleWrite(VarGetType($aArray) & @CRLF) ;Array
ConsoleWrite(UBound($aArray) & @CRLF) ;1

You can access the first (and the last) offset like this:

ConsoleWrite($aArray[0] & @CRLF)

And remember this is not valid:

Global $aArray[0]
ConsoleWrite(VarGetType($aArray) & @CRLF) ;Array
ConsoleWrite(UBound($aArray) & @CRLF) ;0
ConsoleWrite($aArray[0] & @CRLF) ;Error 

Because an array length should logically be at least 1, as an zero length array makes no sense.

It's look like you create a variable which you can't access it.

So an array with the minimum length (1) is just like a normal variable.

That's because of the memory stuff.

In a programming language with multiple datatypes, each datatype has its own length, for example an int variable in c++ is 4 byte length.

When you create an int array like Array[2], you are saying you want 2 * (sizeof(datatype)) bytes to be allocated to the created array.

If the start address of the allocation in the memory be 100 (For example), when you say Array[0], you are saying 100 + (0 * sizeof(datatype)) which is equal to 100, and when you say Array[1] it should be 104 as the datatype is int in this example.

Now think logically, what does an array with a length of 0 could mean?

Edited January 21, 2014 by D4RKON3

[jaberwacky]

It looks to me like you've still indicated that address 100 should still be something.  Ambiguous, could be anything of any size until at such point you've indicated to set aside some amount of memory starting at 100.

[FaridAgl]

I didn't get what you are trying to say, but I'm saying $Array[0] doesn't make any sense.

[Melba23]

D4RKON3,

If I remember correctly it was introduced last summer - I amended the Array.au3 library so that it worked with empty arrays. There had been many discussions about whether AutoIt should allow such a thing - search around the forum to find the discussions - usually ended abruptly by the same person.

One of the major advantages to my eyes is that you can do what I did in the example code above - use ArrayAdd/Delete and not have to worry whether there are actually any elements in the array. Before empty arrays existed, removing the final element destroyed the array - then adding another item meant checking if the variable was an array and redeclaring it if it was not. So I do not agree that empty arrays make no sense.

M23

[water]

There are some UDFs out there that query data sources (AD, Excel ...) if the query string doesn't find any data it is sensible to return an empty array to the calling script.

[FaridAgl]

So, is it just another of the AutoIt's magics which shows up from the AutoIt's mystery box or it's also available on major programming languages like C++, Java or C#?

If yes, then I'm sorry because I never heard about it.

[Melba23]

D4RKON3,

I seem to remember from those previously mentioned discussions that some other languages do indeed have this functionality. They were good reads - it is worth searching for them.

M23

[jchd]

Many languages allow for empty arrays, even if sometimes under a crude form. There is nothing shocking about an empty container. The empty set is crucial in set theory - and in mathematics in general. A linked list or a list can obviously be empty. An array is just another arrangement of things.