[Solved] Why is $a = $b

[UEZ]

Do I missed something or why is $a = $b when $a="" and $b=0?

Local $a = ""
Local $b = 0

If $a = $b Then
    ConsoleWrite("equal!" & @CRLF)
Else
    ConsoleWrite("NOT equal!" & @CRLF)
EndIf

It seems to be that "" is set to 0 in the memory for variable $a...

BR,

UEZ

Edited November 8, 2010 by UEZ

[Juvigy]

One is number the other is a string. It is not good practice to compare them.

You need to convert one to the other type - maybe like this:

$x = Number("3.14") ;returns 3.14

@Edit.

Strings beginning with letters are represented as 0 so:

Local $a = ""
Local $b = 0

If $a = String($b) Then
    ConsoleWrite("equal!" & @CRLF)
Else
    ConsoleWrite("NOT equal!" & @CRLF)
EndIf

Edited May 28, 2010 by Juvigy

[UEZ]

Same when line 1 is: Local $a

$a should be NUL and NUL should not be equal with 0 or?

BR,

UEZ

Edited May 28, 2010 by UEZ

[Yoriz]

• Char = NUL
• Dec = 0
• Hex = 0
• Oct = 000
• Description = Null Character

[MvGulik]

whatever Edited February 7, 2011 by MvGulik

[UEZ]

(re)read Help page "Language Reference - Datatypes" (for starters)

It should clearup a lot should of initial or basic question about AutoIt variable handling/behavior. (strings, numbers and bools)

Good hint:

...If a string is used as a boolean and it is an empty string "" , it will be assumed to equal False (see below). For example, NOT "" equals the Boolean true...

BR,

UEZ

[PsaltyDS]

Good hint:

...If a string is used as a boolean and it is an empty string "" , it will be assumed to equal False (see below). For example, NOT "" equals the Boolean true...

Related, but not exactly what you were seeing in the OP.

You used a compare operator "=" with a numeric, so a numeric compare was done. AutoIt made an attempt to recast "" as a number first, and the empty string evaluated to 0 for that operation.

You could have forced string comparison with "==":

ConsoleWrite("Numeric:  " & ("" = 0) & @LF)
ConsoleWrite(" String:  " & ("" == 0) & @LF)

[UEZ]

The problem occured when I used

...
    If IsObj($colItems) Then
        For $objItem In $colItems
            $NW_DNS3 = $objItem.DNSServerSearchOrder(2)
        Next
    EndIf
    Local $DNS3 = StringStripWS($NW_DNS3, 2)
    Local $chk_text = 0
    If $DNS3 = $chk_text Then
...

$NW_DNS3 was empty because no 3rd DNS search order was not entered but If case was always true!

Local $a or Local $a = "" is a string type -> "Only an empty string ("") will be a Boolean false"

and thus $a = 0 -> If 0 = 0 then is always the case!

Now it is clear to me! I changed $chk_text to "na"

Thanks for your replies!

BR,

UEZ

Edited May 28, 2010 by UEZ