Concatenation and test evaluation badly prioritised ?

[sksbir]

Try this littre script:

msgbox(0,"test0","1=0 --> " & 1=0)  
msgbox(0,"test1","1=0 --> " & (1=0) )   

; EXPECTED : 1=0 --> 0 ....

Test 0 fail : Shouldn't contatenation be evaluated after comparison tests ?

Today, I have to use parenthesis to get it working like : see test 1

Using Autoit 3.1.1.0

[edit] I now understand what is happening :

first, autoit evaluates "1=0 --> " & 1

then compare "1=0 --> 1" = 0

so result is 0

Edited January 18, 2006 by sksbir

[LoWang]

Nobody answered this and yes after 9years I am confused by this strange behavior as well...

$str="something"
if not $str="somethingelse" then dosomething()

does nothing. What is the reason for such strange behavior in autoit? This leads to unnecessary errors and prolongs development time when you have to debug it. Or is there any reason one would want to negate string with not $str?

Edited August 14, 2015 by LoWang

[Danyfirex]

By default autoit evaluation return bool type. it you want number just use int.

 

Please Don't revive old topic. Saludos

[jchd]

What is the reason for such strange behavior in autoit?

This results from the priority of operators. See help file under "Operators".

[JLogan3o13]

$str="something"

if not $str="somethingelse" then dosomething()

Would be more correctly written

$str="something"
If $str <> "somethingelse" then dosomething()

 

[LoWang]

Guys thank you for poingint me to the help pages and manuals, but I understand how to do it right and how it works already.

What I was asking is why is this behavior coded into AutoIt and if there is any specific reason or some advantage in certain situations or type of code which justifies this unusual "feature" of AutoIt programming language. So far I find only a lot of questions around the web with people being confused by this operators priority.

Edited August 17, 2015 by LoWang

[guinness]

So you understand how it works, therefore what is the problem? Also jchd linked to the help file because it explains why it happens and yes it's "behaviour coded into AutoIt"!

Edited August 17, 2015 by guinness
Typo

[LoWang]

Do I need to have a problem to ask a question like that? Or is my curiosity too impolite if I question developers? But if there was no special reason for this default operator priority or the origin of this decision it is no longer known then OK...

Edited August 17, 2015 by LoWang

[jchd]

LoWang,

How exactly the AutoIt operators' priority differs from the languages you know and use and why it's so surprising to you?

[guinness]

if (!'string' === false) { // !'string' is equal to false and then false is compared with false hence true
    console.log('Internet is NOT broken!');
}

This is JavaScript. Therefore if AutoIt is broken, so is the entire web. Maybe contact ECMAScript and W3C and explain to them that they're wrong. Let us know what they respond with so we can change AutoIt. Thanks

[LoWang]

OK OK, thank you for the effort, but your example unfortunately does not show anything, because I don't think strings are usually compared to false and if you add parenthesis

if (!('string' === false)) { // 'string' is not equal to false thus negating it with ! makes true
    console.log('Internet is NOT broken!');
}

it produces the same result...

However when I rewrote my example with comparing string to string to JavaScript I gotta say you are right. I did not know JavaScript's ! had higher priority then comparison 

var str="something"
if (! str=="somethingelse"){
    console.log('something');
}else{
    console.log('! has precedence in Javascript over ==');
}

The same seems to apply to PHP (again it uses exclamation mark instead of not) 

However if you try that in Python:
In [1]: str="abc"                                                                                
                                                                                                 
In [2]: not str=="abcd"                                                                          
Out[2]: True                 

Or Perl:

$str="abc";
if (not $str eq "abcd"){
    print "eq has higher priority then not \n";
}else{
    print "false \n";
}

And here we see something quite interesting. You can use either ! or not as an operator but their behavior is different!

$str="abc";
if (! $str eq "abcd"){
    print "true \n";
}else{
    print "! has higher priority then eq \n";
}

This leads me to a conclusion: 
It looks like languages using "not" instead of ! have it's precedence lower. Unlike those using only ! The main thing which makes higher precedence of exclamation mark obvious is that you can (and usually everyone do) write it without space right after it. On the other hand you cannot usually ommit space after "not" operator (you can in Perl though…). So it seems AutoIt indeed is a bit special because there is no ! as a logical operator and the behavior of not operator is different then in other languages I know of. So thank you for an interesting discussion guys

Edited August 20, 2015 by LoWang