[swift-evolution] Proposal to change Logical NOT Operator from exclamation mark ( ! ) to something else

[Haravikk]

> On 15 Feb 2017, at 22:44, Nicolas Fezans via swift-evolution <swift-evolution at swift.org> wrote:
> 
> > 3: maybe ~ is a better fit?
> 
> just for information this is in line with Matlab in which the following three "not"-related syntax exist:
> a) ~ as a prefix operator for not
> b) not as a function
> c) ~= as an infix operator for "is not equal to"
> 
> I see pros and cons for each option and have a very slight preference for ~ over !.
> 
> I would however avoid ¬ because I would not like to have a character that is not directly accessible on most keyboards for something as simple as a not operation, even if I like these maths notations very much.
> 
> If it would be decided to keep ! I could imagine that  adding syntax coloration in code editors to make both uses of ! look a bit different would help beginners and newcomers. This is more complicated to do than the typical syntax coloration logic in text editors (syntax must be understood for doing that), but this should not be a problem in Xcode.
> 
> If ~ would be preferred, I would recommend to continue accepting ! for one or more versions of swift but with a warning recommending to change it (we do not need to make a source breaking change when it is possible to continue accepting it and to mark it as obsolete)

Tilde is already used in Swift for bit-flipping, though actually on a boolean type (if you treat it as 1-bit) bit-flipping and logical NOT are equivalent, and you can't use logical NOT an Ints at the moment anyway.
So tilde could be a good option, however the ~= operator also already exists in Swift for pattern matching, so couldn't be used as a replacement for !=, unless there's a better operator for pattern matching (personally I don't like using an operator for pattern matching at all but maybe that's just me).

>> On 15 Feb 2017, at 22:28, Derrick Ho via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> There is no need to change it
>> 
>> Since the context basically disambiguates the meaning of !
>> 
>> The next best thing is to compare it to false
>> 
>> (val == false) // same as !val
>> On Wed, Feb 15, 2017 at 3:02 PM David Waite via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> If someone came with a nice syntax I’d be for this. I can’t imagine what that would be.
>> 
>> I doubt there is an alternate prefix or postfix operator that would pass muster, due to ‘!’ already meaning the appropriate thing in so many languages, and swift only supporting symbolic operators.
>> 
>> I can’t think of a method on boolean which would read properly either, e.g.
>> 
>> 	if isValid.not() {…}
>> 
>> The closest I could think to a decent bike shed color would be a global function:
>> 
>> 	if not(isValid) {…}
>> 
>> -DW
>> 
>>> On Feb 15, 2017, at 11:10 AM, Robert Widmann via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>> So you've identified the problem, but what do you propose as a solution here?  
>>> 
>>> It should be noted that a (non-stdlib) language-level answer to this question has already been discussed and rejected (https://lists.swift.org/pipermail/swift-evolution/2015-December/000032.html <https://lists.swift.org/pipermail/swift-evolution/2015-December/000032.html>).
>>> 
>>> ~Robert Widmann
>>> 
>>> 2017/02/15 9:02、Sadiq via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> のメッセージ:
>>> 
>>>> Hello,
>>>> 
>>>> I would like to suggest to change Logical NOT Operator from ! to something else. 
>>>> It will increase the readability of the code and will avoid any confusion with the symbol used for force unwrapping of optional values. 
>>>> It would be easier for new programmers to learn Swift as the first language. 
>>>> I don't understand the rational behind using the same operator for two different purposes. 
>>>> 
>>>> Thanks and Regards,
>>>> Mohammad Sadiq
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