Global, Local, Inheritance of variables

[EdDyreen]

I'm having some serious problems with the concept of inheritance of variables

Local $var = 'hello'
MsgBox( 0, '', '$var=' &$var )
testing()
MsgBox( 0, '', '$var=' &$var )
MsgBox( 0, '', 'endoftest' )
Exit

Func testing()
    Global $var = 'there'
    testing2()
EndFunc

Func testing2()
    MsgBox( 0, '', '$var=' &$var )
EndFunc

$var=hello
$var=there
$var=there
endoftest

Local $var = 'hello'
MsgBox( 0, '', '$var=' &$var )
testing()
MsgBox( 0, '', '$var=' &$var )
MsgBox( 0, '', 'endoftest' )
Exit

Func testing()
Local $var = 'there'
testing2()
EndFunc

Func testing2()
MsgBox( 0, '', '$var=' &$var )
EndFunc

$var=hello
$var=hello
$var=hello
endoftest

What I would like to see is:

$var=hello
$var=there
$var=hello
endoftest

I do not like to use arguments as a work around, but I might have to,

I'm not sure but I have a feeling autoIT does not know about the concept inheritance ?

Any help is greatly appreciated.

Edited May 12, 2012 by EdDyreen

[MilesAhead]

I don't know what "inheritance" you are talking about. What your test scripts demonstrate is scoping. If you read the help it suggests avoiding local and global vars with the same names if possible. That's why in UDFs you see those little prefixes on the variable names.

If you use Global inside a function to make a global when you already have a variable of that name defined in that scope, it's going to be bumped. See the help for scope search order with variable name clashes.

Inheritance is an OOP mechanism. A totally different animal.

Edited May 12, 2012 by MilesAhead

[Spiff59]

There's really no such thing as a Local variable that is created outside of a function.

Your initial Local declaration is treated as a global and accessible from within called functions.

Local $var = 'hello' ; really a global
MsgBox( 0, '', '$var=' & $var )
testing()
MsgBox( 0, '', '$var=' & $var )

Func testing()
    $var = "goodbye" ; updating external global
    Local $var = "greetings" ; creating new local variable, temporarily replacing global
    MsgBox( 0, '', '$var=' & $var )
EndFunc

Edited May 12, 2012 by Spiff59

[EdDyreen]

I was thinking about something like

set $var = 1
setlocal
   set $var = 2
   setlocal
      $var = 2
   endlocal
   $var = 2
endlocal
$var = 1

I see no other way than useing a stack to make variables persist through functions

Global $stack[1]
Global $var = 'hello'
MsgBox( 0, '', '$var=' &$var )
testing()
MsgBox( 0, '', '$var=' &$var )
MsgBox( 0, '', 'endoftest' )
Exit

Func testing()
ReDim $stack[ UBound( $stack ) + 1 ]
$stack[ UBound( $stack ) - 1 ] = $var
Global $var
$var = 'there'
testing2()
$var = $stack[ UBound( $stack ) - 1 ]
ReDim $stack[ UBound( $stack ) - 1 ]
EndFunc

Func testing2()
ReDim $stack[ UBound( $stack ) + 1 ]
$stack[ UBound( $stack ) - 1 ] = $var
Global $var
MsgBox( 0, '', '$var=' &$var )
$var = $stack[ UBound( $stack ) - 1 ]
ReDim $stack[ UBound( $stack ) - 1 ]
EndFunc

Edited May 12, 2012 by EdDyreen

[water]

I would pass all variables I need in a function as parameters.

[EdDyreen]

I understand 'water', there are subtile differences that make me not want to do that

- I want to be able to acces $var at any time from within any function, so all functions would require the parameter.

- I sometimes may want to change $var and return another variable ( without having to resort to arrays ).

I can simplify the stack method by using 2 more functions like

Global $stack[1]
Global $var = 'hello'
MsgBox( 0, '', '$var=' &$var )
testing()
MsgBox( 0, '', '$var=' &$var )
MsgBox( 0, '', 'endoftest' )
Exit

Func setLocal_( $setLocal )
    ReDim $stack[ UBound( $stack ) + 1 ]
    $stack[ UBound( $stack ) - 1 ] = Eval( $setLocal )
EndFunc

Func endLocal_( $endLocal )
    Assign ( $endLocal, $stack[ UBound( $stack ) - 1 ] , 2 )
    ReDim $stack[ UBound( $stack ) - 1 ]
EndFunc

Func testing()
    setLocal_( 'var' )

    $var = 'there'
    testing2()

    endLocal_( 'var' )
EndFunc

Func testing2()
    setLocal_( 'var' )

    MsgBox( 0, '', '$var=' &$var )

    endLocal_( 'var' )
EndFunc

It's ugly, but it works

Edited May 12, 2012 by EdDyreen

[jchd]

Passing a var ByRef allow changing its value outside the called function.

Else and if, definitely, there is a real, absolute, need to make a given variable global, then make it global*.

* but is that necessary?

[kylomas]

Ed,

You may be over complicating this. You have four options

1 - use byref

2 - use "global" definition inside of function

3 - use unique variable name declared "local" outside of any function (makes it "global" in scope)

4 - use a parameter

While I think using the same variable name across multiple scopes is a poor programming technique, the following code demonstrates this using a function parameter

;
;
local $var = 10
consolewrite('$var declared outside of any function (scope = script) = ' & $var & @lf)
consolewrite('$var returned from function (scope = function)         = ' & _func01() & @lf)
consolewrite('$var declared outside of any function (scope = script) = ' & $var & @lf)
func _func01()
consolewrite('$var in func01 b/4 local definition (scope = script)   = ' & $var & @lf)
local $var = 05
consolewrite('$var in func01 aft local definition (scope = function) = ' & $var & @lf)
return $var
endfunc

Good Luck,

Kylomas

Edit : error in code fixed - this is not a "function parm" but demonstrates the principle.

Edit2: code example using a function parameter

;
;
local $var = 10
consolewrite('$var declared outside of any function (scope = script) = ' & $var & @lf)
consolewrite('$var returned from function (scope = function)         = ' & _func01(5) & @lf)
consolewrite('$var declared outside of any function (scope = script) = ' & $var & @lf)
func _func01($str)
 consolewrite('$var in func01 b/4 local definition (scope = script)   = ' & $var & @lf)
 local $var = $str
 consolewrite('$var in func01 aft local definition (scope = function) = ' & $var & @lf)
 return $var
endfunc

Edited May 13, 2012 by kylomas

[ProgAndy]

If you need this strange scoping behaviour, then you are doing something wrong. A clean scoping schema only uses

- global scope

- namespace scope (use a prefix in AutoIt)

- module/file scope (AutoIt: emulate with a namespace, prefix)

- block scope (limited in AutoIt: no classes, no nested blocks, only functions as blocks)

If you want to build object-like behaviour, then you should use a ByRef-parameter with an array or a dictionary object

[EdDyreen]

I use an array that keeps track of functions, I also use a variable that can be switched on and off, when switched on, all nested functions inherit this value, but when the function that made the switch is left the previous value is taken.

$array = null
$varry = null
call function1
$array = null
$varry = null

function1
  set $array = $array, function1
  $array = function1
  $varry = null
  call function2
  $array = function1
  $varry = null
endfunc

function2
  set $array = $array, function2
  $array = function1, function2
  $varry = null
  set $varry = function2
  call function3
  $array = function1, function2
  $varry = function2
endfunc

function3
  set $array = $array, function3
  $array = function1, function2, function3
  $varry = function2
endfunc

@ProgAndy, where can I find some in depth information on

- namespace scope (use a prefix in AutoIt)

- module/file scope (AutoIt: emulate with a namespace, prefix)

- block scope (limited in AutoIt: no classes, no nested blocks, only functions as blocks)

Thanks for your time

Edited May 13, 2012 by EdDyreen

[ProgAndy]

@ProgAndy, where can I find some in depth information on

- namespace scope (use a prefix in AutoIt)

- module/file scope (AutoIt: emulate with a namespace, prefix)

- block scope (limited in AutoIt: no classes, no nested blocks, only functions as blocks)

Here? http://en.wikipedia.org/wiki/Scope_%28computer_science%29

A namespace in its simplest form can also be seen as an extension of the variable name. This can be represented with a prefix like $WINAPI_... Since there is no way to declare variables as private, this is covered with another naming rule (prefix the name with an underscore: $_WINAPI_...)

[EdDyreen]

It is now clear to me, this behavior is not default nor can it be easily simulated,

the only way I see possible to simulate this behavior ( value is visible to children but not to parents ) is by using a stack.

Thanks for making me understand,

Edited May 13, 2012 by EdDyreen

[kylomas]

Ed,

Just curious, why do you think that you need to mimic oop behavior?

kylomas

[EdDyreen]

I am exploring a debugging mechanism that could work for autoIT,

1 the program terminates succesfully

2 the program crashes

_1 All relevant information about the crash is shown onscreen for later debugging

___-An array containing a list of all nested functions called

___-The errorcode + errortext if any

3 the program hangs and has to be terminated manually

2-3

_1 the debugger is switched on before the misbehavior occurs

_2 all relevant information is shown onscreen

___-enters 'this' function

___-relevant variable contents

___-leaves 'this' function

Edited May 13, 2012 by EdDyreen

[jchd]

While the basic idea is valuable, AutoIt doesn't bend easily to such exhumation.

I'm just giving my opinion: a much robust way to code routinely serious programs is to properly handle errors at the moment they occur (such as a file locked by another process, I/O error, any unexpected error cause). All "internal" errors (like the classical index of array out of bound) are not errors in my view, but programming mistakes.

Instead of making your code massively complicated and harder to maintain by using "where did I goof in fact?" post-mortem technique, place your focus in checking invariants. I almost never saw any use of _Assert in code published here, but this is a much safer/cleaner way to explicitely check subtle conditions you have doubts on hard-to-chew logic. Once you get confidence that your code is correct (it doesn't seem like, but "correct" is a very strong word in algorithmics), it's very easy to comment out all _Assert lines (edit: or comment out _DebugStartup). Note that this still doesn't prove your code correct: that would require formal methods that are even one (huge) step higher in abstraction.

EDIT: btw, there is a good visual debugger in the example scripts.

Hope you don't mind a diverging opinion!

Edited May 13, 2012 by jchd

[MvGulik]

Mmm. Sounds very similar in behavior to what my Debug_Timer() thingy is doing.

Anyway ...

Func MyFunction ( parm1, parm2, ... )

    If $gDEBUG = True then
        if parm1 = ... then ...
        assert ... (erm ... ) something
    endif

;; main function code

EndFunc

Edited May 13, 2012 by MvGulik

[water]

Error checking should be part of every script you use in production. Check the return value or @error after every function call to be sure that you can savely process the next statement.