The Mystery of -=

[t8inevergreen]

So, we all know that operators like += and &= work in AutoIt...

But why does -= throw a syntax error?

[evilertoaster]

$a=5
$a-=2
MsgBox(0,"",$a) ;shows 3

No problems here.

[GEOSoft]

I don't see a problem. Try this test

$i = 1
MsgBox(0, "results", "$i = " & $i)
$i += 1
MsgBox(0, "results", "$i = " & $i)
$i -= 1
MsgBox(0, "results", "$i = " & $i)

[t8inevergreen]

Hmm, that does seem to work.

In my situation, I was doing this:

Global $ArrayMax -= $MultiList[0]-1

Where $ArrayMax and $MultiList[0] are guaranteed numbers.

[evilertoaster]

You can't add or subtract something that hasn't been assigned yet...

[GEOSoft]

What do you get with this?

Global $ArrayMax -= $MultiList[0]-1
MsgBox(0, "Results", $ArrayMax)

Actually that line looks screwy. What were you expecting as a return? What is the size of the array?

EDIT: And what evilertoaster said

Edited March 11, 2009 by GEOSoft

[Richard Robertson]

Dump the global and see if it works. When you redeclare it, it might be wiping the value.

[t8inevergreen]

Richard Robertson: THANKS! That made it work, and now that I look at it, the Global was unnecessary.

And to answer the questions of Evil Toaster and GEOSoft, that line was just an excerpt from a little algo that found duplicates or accidentally included files in a list of daily log files, the line where the syntax error was thrown.

-$ArrayMax was the Ubound value of the list array and the maximum for my For loop that compared each list item to the one below it after being sorted by the incredibly useful ArrayNatural UDF.

-$MultiList was the array of duplicates that was populated after a single duplicate was found and a While loop was run to find any further duplicates below.

Both values are dynamic, but both were declared beforehand and were guaranteed to be numbers.

Thanks for your help everyone!