Constant keyword, does it have use when I create code for myself?

[guinness]

That has to be the most painful piece of code I have written in a very long time. I initially was using regular expressions but it became complicated and hard to manage, so then I decided to use the string functions. I'm quite proud of what I have achieved so far with this.

[czardas]

Regarding using the const keyword. I am under the impression that it is not good practice to use this keyword simply because a variable does not get modified. The reason is bloat related: there is no need to get the interpreter to do any more work than necessary. Of coure a global variable within a large script accidentally being modified is a possibility, but I don't think a local variable within a five or six line function need to be declared constant. I believe this is nothing more than a trade off between optimization and readability.

[guinness]

That's my reason behind asking, though I honestly don't think it makes any difference in terms of speed.

[czardas]

I'll test it and see.

[guinness]

OK.

[czardas]

Indeed you are right (close enough anyway). In the tests, the function using Const declaration lags behind just a tiny little bit. The difference is approximately half of one percent, which is negligible.

$iTimer = TimerInit()
For $i = 0 To 100000000
    _F1()
Next
ConsoleWrite(TimerDiff($iTimer) & @LF)

$iTimer = TimerInit()
For $i = 0 To 100000000
    _F2()
Next
ConsoleWrite(TimerDiff($iTimer) & @LF)

Func _F1()
    Local $vVar = 0
EndFunc

Func _F2()
    Local Const $vVar = 0
EndFunc

Results:

196117.419392688

197127.06894312

Still, I would only use Const to declare a variable if modifying it is undesirable, or in some way erroneous. My main objection to using Const all the time is that it makes it harder for developers to modify your code in the future, plus the bloat factor. Someone might want to change the value. Perhaps I'm missing something, so please educate me (and others) by sharing your knowledge.

Edited February 13, 2013 by czardas

[guinness]

3 minutes of testing, wow. Thanks.

[czardas]

Yes it was too close to leave to chance. I should run it longer to make sure, but it's such a small difference to really be concerned about.

Edited February 13, 2013 by czardas

[guinness]

Well even reducing to 1000 iterations, I found the results to be similar.

[FireFox]

I would be happy if we could declare a variable as a constant (without assigning a value), and then be able to assign a value (only one time of course).

;like this
Global Const $hMyGUI, $tbMyInput, ...

$hMyGUI = GUICreate(...

$tbMyInput = GUICtrlCreateInput(...

;instead of
Global Const $hMyGUI = GUICreate(...

Global Const $tbMyInput = GUICtrlCreateInput(...

Edited February 13, 2013 by FireFox

[guinness]

I would find that incredibly difficult to read and I'm sure this doesn't happen in other languages either.

If I had one wish for AutoIt, I would wish that all veriables be declared and initialised before usage.

[czardas]

I think the prefix 'k' as in $k_Var would be a good way to indicate a constant. Just an idea which, you may like, or not.

Edited February 13, 2013 by czardas

[guinness]

I think the prefix 'k' as in $k_Var would be a good way to indicate a constant. Just an idea which you may or like or not.

Did you make that up? Wouldn't $csString be more appropriate?

FireFox's suggestion would also break the "rule" of declare when they are needed. I used to make the awful habit of doing this

Local $hGUI, $iOKButton, $vVar

$hGUI = GUICreate(...
$iOKButton = GUICtrlCreateButton(...
$vVar = 'Some variant'

[czardas]

Did you make that up? Wouldn't $csString be more appropriate?

No I didn't make it up. Constants are usually denoted by the letter k in maths and physics.

I believe it would be more fitting to stick to universal standards, unless a different precedent has already been set in programming. Then I would probably select the most commonly used indicator.

Edit

See what Mat thinks.

Edited February 13, 2013 by czardas

[guinness]

OK, I couldn't find it in the table for Hungarian notation, that's why I asked.

[Spiff59]

In compiled languages, if you explicitly state the constness of variables (and the compiler can guarantee this), the compiler is able to do a lot of optimizations on code, registers, memory layouts, copying (specifically able to do reference passing instead of copying parameters) etc.

That was my take-away from my COBOL days... that constants were stored and referenced more efficiently and resulted in saving a couple bytes and a couple instructions.

As someone else stated, it's probably not the case with AutoIT. So it seems their only use here is to "lock" a variable that you already know you don't intend to modify. Kind of like wearing body armor when you're slicing onions. You know you've no intention of plunging the paring knife into your heart, but you don't trust yourself enough to slice them unprotected.

[guinness]

I suppose that analogy works as well.

[guinness]

Another idea that came to mind, is maybe AutoIt optimises constant variables because the memory size is static and doesn't have to allocate any more memory than is required. This is just an idea of course.

[guinness]

Oh and I finally got around to finishing my constant checker to determine whether or not a variable is re-assigned a different value.

[BrewManNH]

A constant checker? Doesn't declaring it as a constant inherently prevent it from being changed?