global variable or function?

[Guest]

Anyway, guess what? Why makes it complicated?
It can work your way, I mean that it will add g_ to any global variable  even if g_ is already exists in the variable.

And then it will change all the variables and functions to a shorter name (This is the ultimate goal in the end when you use Au3Stripper)

 

Example -

Suppose we have this code

Global $g_var1, $g_var2, ...

Func SomeFunc()
    Local $var1 = 1
    Local $var2 = 2
    ...
EndFunc

At first it will change it to:

Global $g_g_var1, $g_g_var2, ...

Func SomeFunc()
    $var1 = 1
    $var2 = 2
    ...
EndFunc

And then it will change it to something like this:

Global $a, $b

Func _a()
    $c = 1
    $d = 2
    ...
EndFunc

So the simple way is more safe

[guinness]

 

There is no other variable, just the one as demonstrated here...

Global $SomeVariable = 10

_Func()

ConsoleWrite($SomeVariable & @LF)

Func _Func()
    $SomeVariable += 10
    ConsoleWrite($SomeVariable & @LF)
EndFunc

JohnOne was expecting the assignment only variable ($SomeVariable = 10) in the function to be considered local.

[czardas]

@gil900 - I think it's better to write code using sensible names to begin with. Using $g_ has been recommended but it is not infallible and neither is it forced. Adding additional prefixes is not quite as straight forward as it sounds. Global replacement of all variables using unique names is more straight forward. Having to differentiate between variable scope adds an extra layer of complexity. Without deep analysis it is very easy to break things.

The scope of a variable very much depends on the whereabouts of declaration. Look again at >#54. If you run the examples in reverse order (within the same script), the result will different. You will get something similar to what is happening in the code posted by JohnOne. This is just one of several possible scenarios which may occur.

Edited January 18, 2015 by czardas

[TheSaint]

Coming mostly from VB, when I first started programming with AutoIt, and of course not schooled in any way, I'd just naturally slipped into using Dim for everything ... and at that point, I wasn't skilled enough to consider using Local.

Anyway, several years ago, Valik gave a discussion about Dim, Local and Global, and basically said you shouldn't be using Dim, so I took that on board, like many others no doubt, and have been using Global ever since, except on the few occasions where I need to use Local.

Whenever I need to use the same named variable for different instances but same purpose, I use Local inside a function, else I just stick to using Global at the start of all my scripts. I make it a rule, to never use the same named variable for any more than one declaration, so in other words, I would never have $var declared as Local as well as Global. I might have two or more $var as Local though ... as in a function that gets a File and/or Folder list.

It just seems simpler and less troublesome to declare virtually all variables as Global at the beginning of a script ... any required differently named Local declarations aside.

Having read much of the conversation to this point, I realize most of you think I should really be paying more attention to scope, and not wastefully use Global like I do. To be honest, I don't understand the impact of the supposed waste. Would one of you care to explain that to me?

P.S. I've kind of felt, that except where I really obviously need to (Local declaration), that it is just a waste of time or mental processes to worry about scope, when especially for all the years I've been coding now, I don't recall ever being bitten for it. The only exceptions of course, is where I have mistakenly reused a variable ... soon fixed.

[guinness]

Would one of you care to explain that to me?

In most cases (with programming languages and/or scripting languages) it's to do with memory management, in which you specify the lifespan of how long a block of memory is reserved for the executable by the system. On MDN the memory life cycle hits the nail on the head.

Note: If you just declare all variables in Global then it's no different to using Dim, which wasn't the point Valik was trying to make in the article he posted.

[Guest]

TheSaint

most of you think I should really be paying more attention to scope, and not wastefully use Global like I do.

 

I am also one of them (Although I do not always do what they say)

Why not use this method:

Func Func1()
    If Not IsDeclared('g_func1_var1') Then
        Global $g_func1_var1, $g_func1_var2, $g_func1_var3 ...
    EndIf
    [code]
    ....
EndFunc

This way it is easy declare global variables at the lowest scope so it should not be big deal with this method

[guinness]

gil900,

That's a poor usage example of IsDeclared, which should only be used with Assign and Eval respectively. If you (the author) can't remember whether or not you declared the variable already, then I am afraid there there has been some misunderstanding as to how you should code.

Edit: Even the help file explains this.

Lowest scope possible means this...

; Global $sSomeVar = "" <= Not used anywhere else but the Example function.

Func Example()
    Local $sSomeVar = "" ; Hence we place it here in the lowest scope possible.
    If True Then
        Local $iAge ; This variable is only used in this "block" so we declare in the lowest scope possible.
    Else
        ; Code
    EndIf
EndFunc

Func SomeFunc()
    ; Code
EndFunc

Edited January 18, 2015 by guinness

[BrewManNH]

It's a really bad idea to declare global variables inside functions.

BTW, you're not declaring anything at the "lowest scope" you're declaring them as global which is the exact opposite of lowest scope.

[Guest]

Ok.
I probably did not understand exactly what "lowest scope" means.

 

It's a really bad idea to declare global variables inside functions.

The logic behind my example is that not always necessary to declare a global variable.
If I have a function which uses global variables(that used only by this function). And the function is not always called, so why declare these global  variables if I don't always call the function (and use these variables).

In this case, when I know that the function will not run always run I prefer to declare its global variables only when it needed..

If I do not do that, then when the function will never run, I declares its global variables for nothing and wastes more ram.

Edited January 18, 2015 by Guest

[guinness]

Lowest scope possible can be translated as where the variable is actually needed/used. If you declare those variables at the top of the script then why the need to check in the function? The interpreter has already declared these for you.

[Guest]

Lowest scope possible can be translated as where the variable is actually needed/used. If you declare those variables at the top of the script then why the need to check in the function? The interpreter has already declared these for you.

 

If one of the variables is large array then it can take memory..

So it is better to declare this kind of variable only when necessary.

But I changed my mind.

I can declare all global variables at the top of the script without always having to assign them any value (like a large array).

And assign to them the value only when it first needed.

This should be a better way

 

Edited January 18, 2015 by Guest

[guinness]

Yes, correct.

[BrewManNH]

You're declaring variables that should be local as Global, if they're only used in that function don't declare them as Global.

 

The logic behind my example is that not always necessary to declare a global variable.
If I have a function which uses global variables(that used only by this function). And the function is not always called, so why declare these global  variables if I don't always call the function (and use these variables).

In this case, when I know that the function will not run always run I prefer to declare its global variables only when it needed..

I'm starting to think you don't know what is supposed to be global and what is supposed to be local.

[Guest]

You're declaring variables that should be local as Global, if they're only used in that function don't declare them as Global.

I'm starting to think you don't know what is supposed to be global and what is supposed to be local.

 

 

that used only by this function

I knew that it will create more questions.

I know what I'm talking about ..

There is such a thing - Function which must have some global variables that used only by this function.

I speak from my little experience I have

This is a very bad example of such a function(Because is written very bad and long time ago but that's not the point ..)

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Edited January 18, 2015 by Guest

[guinness]

There is such a thing - Function which must have some global variables that used only by this function.

Erm...I am having my doubts too as this comment is wrong. If you have variables that are used by that function only, then they definitely should NOT be global. Now if you mean they should retain the data when the function is complete e.g. returned from, then that's a different thing and we're into discussing the likes of Static keyword usage.

Edited January 18, 2015 by guinness

[Guest]

Erm...I am having my doubts too as this comment is wrong. If you have variables that are used by that function alone, then they definitely should be NOT global. Now if you mean they should retain the data when the function is complete, then that's a different thing and we're into discussing the likes of Static.

 

Look at the example that I posted.

Do you think it could be done(that the function will run without independent loop) without global variables?

 

Even if knew at 2013 about AdlibRegister I still was has to use global variables in order to achieve that

 

Edited January 18, 2015 by Guest

[guinness]

What example? The beep function? Yes, you can create that example without using the Global keyword. Did you check Local Static (Static being something I don't think you know).

[Guest]

If I'm not mistaken, Static mean that the value can not be changed.

How can this be done without global variables?

 

I know there is no need to create global variables when this function does not run as part of the main loop.

But if the function need to run as part of the main loop (so all code in the main loop will keep runing while the function running), I don't see way how not to use some global variable.

 

how this kind of function:

Do 
    ; Code ...
Until Not Function1() ; A function that need more loop cycles in order to finish the task. (for example function that using TimerInit() and TimerDiff()

Does not have to use global variables?

This kind of function exit again and again so every local variable (Such as TimerInit variable)will reset because it is local and not global.

 

EDIT:
Now I'm starting to understand how it can be donw with "Static"

It appears that everything I thought about "Static" was worng..

Thank you very much for this useful information

Edited January 18, 2015 by Guest

[guinness]

 

EDIT:

Now I'm starting to understand how it can be donw with "Static"

It appears that everything I thought about "Static" was worng..

Thank you very much for this useful information

 

Good. Hopefully the help file is clear about this.

[czardas]

I tend to do the exact opposite of TheSaint. I avoid globals and use encapsulation as much as I think reasonable. I nearly always win the battle and end up with no possible leaks plus minimum overhead. I only use global variables if I can see no alternative. This may apply less when there is a team of developers needing access to the same Constants. So for me the answer to the original question (global variable or function) would always be the latter. Since most of my variables are declared local, the code can be encapsulated using additional functions without  the need for any modification. I just copy and paste the ready to run code. On the other hand, if I do decide to use a global variable, it's always a design choice and hardly ever a workaround.

Edited January 19, 2015 by czardas