Is it taboo to have a variable be declared twice?

[DoubleMcLovin]

I have Opt('MustDeclareVars', 1) turned on for good practice, and I was wondering if it is bad practice to allow a variable to be "declared" (like Local $var) multiple times as the sript runs through it's While loop.

[Melba23]

DoubleMcLovin,

If I correctly remember a Dev's answer to a previous question like this, you slow down the loop if you declare the variable each time you pass through it as AutoIt has to check if the variable has already been declared on every pass. So better practice would be to do as Deathbringer suggested and declare it the once before the loop starts.

If you declare a variable within a single conditional statement, you should always declare it first, as if the condition is not met you will not run the line of code containing the variable declaration and thus are very likely to get an error. If there are multiple conditions I tend to declare the most likely value of the variable first and then change it if needed - something like this:

; Rather than this:
If $fFlag = True Then
   Local $vVar = 1
Else
   Local $vVar = 2
EndIf

; I do this
Local $vVar = 2
If $fFlag = True Then $vVar = 1

Then the variable is always declared - and AutoIt may have fewer conditions to evaluate.

M23

[guinness]

As Deathbringer mentioned I always use #AutoIt3Wrapper_Au3Check_Parameters=-q -d -w 1 -w 2 -w 3 -w 4 -w 5 -w 6 and this has helped me understand declaration of variables a lot better, but didn't realise that declaring a variable in a loop could cause the loop to slow down.