AutoIt v3.3.13.11 Beta

[czardas]

It was done because people were abusing the fact that Default evaluated to -1.  Passing Default to GUI controls, and created functions that took a numeric parameter and checking for -1 rather than explicitly checking for Default. Or the other way around and checking for Default but the user passing -1.

Any evaluation of a number to try and guess if it is Default is wrong. Apart from triggering a fatal error, the only sensible number we can assign is 0. Not because it is more likely to be significant (it's not, -1 is more abnormal) but because it is more likely to be confused with an actual 0. That makes it more likely that the only sensible use of Default is to indicate one thing, the Default keyword.

The correct use of testing for Default is:

If $something = Default

This will never fail because the user passed a number instead. 

 

I appreciate you taking time to explain this Jon. I didn't mean to come across as being critical. I understand your decision better now. I really just wanted to understand it to avoid making mistakes in my own design choices. Thanks.

Edited July 30, 2014 by czardas

[czardas]

What if Default gives the optional params of a function their optional value?

 

You may wish to assign a default optional value using a function call. That function could be anything (based on conditions), and it may complicate things too much - both to implement and for beginners to work with. I would say it is currently very flexible, even if it is slightly verbose.

Edited July 30, 2014 by czardas

[jchd]

eukalyptus,

I've proposed that several times but received little interest and even rebutal. I can't get why Default shouldn't work this way.

[czardas]

But could it be made to work flexibly like this?

:

Func ConditionalDefault($vDefault = 0xFFFFFFFF)
    Local $iCondition = Random(0, 1, 1)
    
    Switch $iCondition
        Case 0
            If $vDefault = Default Then $vDefault = FalseCondition()
        Case 1
            If $vDefault <> Default Then $vDefault = TrueCondition()
    EndSwitch
    ; some code
EndFunc ;==> ConditionalDefault

Edited July 30, 2014 by czardas

[Richard Robertson]

If $a <> $a Then ; $a Must be null

And no, I'm not making that up.

$a could also be NaN or ±Infinity. Floating point non-numbers don't equal themselves either.

Edited July 31, 2014 by Richard Robertson

[jchd]

Correct! That's why SQL IsNull (and IsNotNull) is useful.

Edited July 31, 2014 by jchd

[Mat]

$a could also be NaN or ±Infinity. Floating point non-numbers don't equal themselves either.

Infinity can be compared without issue.

You are right about NaN though. In reality, why you'd have a situation where you weren't sure if a variable was Null or NaN I don't know. 

[jchd]

Indeed I didn't check +/- Inf. Maybe that depends on some flag setting in the FP unit but I won't check further.

Anyway If $x = Null works everytime and is both clearer and simpler than If IsKeyword($x) = 2.

[Richard Robertson]

Yeah, I'm used to checking equality with null from other languages.