Ternary Operator Syntax - throwing errors

[bailey1274]

Can someone please explain why this expression keeps throwing errors? I've tried so many different combinations of parentheses around each part/the entire expression. 

For $row = 0 to UBound($aTableData,1)-1

    (Mod($row,7)=0) ? (Null) : (ContinueLoop)

This gives "Error: Missing right bracket ')' in expression"

Sometimes with other parentheses combinations I just get 'Error in expression' which I'm assuming is just a syntax error but at this point I'm not sure.

The $aTableData is an array of 100+ rows and the oddest part is that when $row = 0, the expression evaluates as expected but when it moves on, I keep getting these errors. It works fine with a plain If-Then statement so I'm assuming this has to be syntax.

[Danp2]

I'm not sure that you can use the ternary operator in this manner. AFAIK, it's designed to return a value, not execute a command.

[seadoggie01]

Why not use this one liner...

If Mod($row, 7) <> 0 Then ContinueLoop

... instead? Using ternary operators is strange when you don't want to return something from them.

Edit: Was ninja-d.

Edited August 29, 2019 by seadoggie01

[bailey1274]

Well yeah, this works like I mentioned in the post but I'm more just curious why its not working.

[bailey1274]

So ternarys will only work in return statements and not just a simple command? Why does it work in a message box like in the example? And that adds to the confusion on why the first iteration works and the following ones do not. 

[seadoggie01]

The issue is that the result isn't being used... you're returning Null or ContinueLoop... to nothing. The example shows the result being posted to the message box, where it's used in that code.

[bailey1274]

Ah so on the first iteration, returning Null works as I would hope because that causes nothing to happen. However on $row=1, it returns a ContinueLoop but does not actually execute it and this somehow causes an error. I get it a little more now, but still a little hazy on why I get that specific error message. Although I guess either way, I'm using it in the wrong context.

[seadoggie01]

Are you using SciTE? I can't even get the code to execute once, AU3Check throws a bunch of syntax errors. I highly suggest installing it, it's great for finding errors before you start

[Jfish]

I think if you use a variable to store the result of the ternary operation it should work  ... just preface your ternary with something to capture it and it should execute the function.  Some examples below.

$number = 5

$result=(Mod($number,2)<>0) ? (MsgBox(0,'',"odd")) : (MsgBox(0,'',"even"))


$functionResult=(Mod($number,2)<>0) ? _helloTernary() : (MsgBox(0,'',"even"))

func _helloTernary()
    for $a=0 to 9
        ConsoleWrite("This function is working!  You selected an odd number"&@CRLF)
    Next
EndFunc

 

[iamtheky]

Isnt part of the issue that ContinueLoop is not a thing that returns a thing?

There are some old lengthy threads by @guinness where he gets religious about ternary not being a replacement for If/Then.  I think this sort of example is part of that.

Edited August 29, 2019 by iamtheky
i am confusing af

[seadoggie01]

@Jfish Even that doesn't work with ContinueLoop, I tried just to be sure. You'll get an error about a missing/mismatched parenthesis --> (

[bailey1274]

This does seem like a good example why its not just a replacement for any if-then. And imo creating a new variable sort of defeats the purpose of being a shorthand as you're doing something extra to make it work. I'm too lazy for all that. My takeaway, just use ternarys for returning values and not executing things.

[mikell]

Iamtheky is right : nothing returned => error
The example from Jfish is not good because Msgbox always returns a value, and user funcs return 0 (if nothing else is specified)
An easy test : remove the parenthesis and you'll get "Error in expression" 

For $i = 1 to 4 
 $i <> 2 ? Msgbox(0,"", $i) : ContinueLoop
Next

 

[jchd]

The ternary operator is special.  One might think it evaluates to a RHS, whatever dataype it is.
But it's not that simple, maybe because it has been introduced lately in the parser.

One would think the two snippets below are equivalent (and both incorrect), but only the second one correctly raises a runtime error:

For $i = 0 To 3
    $i = 2 ? 42 : 42
Next

For $i = 0 To 3
    42
Next

Also ContinueLoop is a statement (like Exit, Wend, EndIf, Select, ...) so it's illegal as a RHS value.

[guinness]

On 8/29/2019 at 8:01 PM, iamtheky said:

Isnt part of the issue that ContinueLoop is not a thing that returns a thing?

There are some old lengthy threads by @guinness where he gets religious about ternary not being a replacement for If/Then.  I think this sort of example is part of that.

Yep, my opinion hasn't changed on that one!

[Danyfirex]

Ternary operator is for evaluating expressions.  ContinueLoop or ExitLoop are statements.

It's like you try to pass ContinueLoop  to a function  as parameter ( Cos(ExitLoop)) or you try to operate with a statement  like ( $var=1+ContinueLoop)

Saludos

Edited September 15, 2019 by Danyfirex

[rudi]

You can use ternary to execute two different "all-in-one-commands", depending on a true/false value.

 

I use that for setting Opt() values depending on if the script is compiled or not.

Just "trow away" the returned result value by assigning it to a not used variable:

$trash=@Compiled?(opt("trayautopause",0)):(opt("Trayicondebug",1))
; MsgBox(0,@Compiled,"check tray icon now")