Fwd: operators !=

[Samuel Gaist]

Answer from Aaron

Begin forwarded message:

> From: "Aaron J. Seigo" <aseigo at kde.org>
> Subject: Re: operators !=
> Date: 25 août 2014 10:12:11 UTC+02:00
> To: Samuel Gaist <samuel.gaist at edeltech.ch>
> 
> On Monday, August 25, 2014 09.17:03 you wrote:
>> So if we expend this thing a bit, it might look like:
>> var x != 3;
>> which would be the same as:
>> var x = !0x03;
>> which would translate to
>> var x = 0xFB;
> 
> That's an interesting interpretation, and one of the reasons I'm uncomfortable 
> with defining '!=' as the literal antonym of '=' in all manners.
> 
> But no, != is a boolean operator only allowing for "assignment on not equals". 
> It leads to visually "strange" things like:
> 
> var x != 3;
> 
> which would be functionally equivalent to:
> 
> var x = 3;
> 
> This follows from:
> 
> var x = 3;
> (x, var y) = [4, 2]; 
> 
> Element 0 does not equal 3, so y is not assigned and we get an error. There 
> are more complex use cases where this becomes actually useful in a non-trivial 
> manner.
> 
> Now, if != is the literal antonym of =, then we get things like this:
> 
> var x = 3;
> (x, var y) != [4, 2]; 
> 
> Element 0 does not equal 3, so y gets assigned. That can be useful and is 
> nicely consistent with how '=' is used in pattern-matching assignment. 
> Unfortunately it also leads to trivial cases that will not behave as most 
> people would expect on first glance:
> 
> var x != 3;
> 
> Variable x is not yet bound to a value, so != always succeeds and assigns 3.
> 
> It's the trivial case that looks odd, while the non-trivial cases (where 
> pattern-matching assignment actually becomes sensible) look sensible.
> 
> Honestly, I'm torn between:
> 
> 	a) != is an antonym of =
> 	b) != means "not equals", has nothing to do with assignment, breaking 
> symmetry with =
> -- 
> Aaron J. Seigo