[swift-evolution] [pitch] adding toggle to Bool

[Eneko Alonso]

I am yet another one that tries to never use !

It feels like bad heritage from C, and it probably should be removed from Swift in the same way for(;;) and ++/-- where removed. 

! does not provide any unique functionality, as it is redundant to “== false”. Other than syntax sugar, it does not add any value to the language. 

I feel a mutating toggle(), invert() or flip() method on Bool provides much more value. The non-mutating counterpart however should probably not be included in the standard library, as it would also be redundant to “== false”. 

Eneko Alonso 

> On Jan 12, 2018, at 14:34, Anders Kierulf via swift-evolution <swift-evolution at swift.org> wrote:
> 
> I also avoid using ! for negation when possible, and `toggle` or `invert` will be helpful, but in many cases I think the negative case is better expressed directly. For example, I find that using `nonEmpty` instead of !isEmpty makes the code easier to read: 
> 
>  extension String {
>      var nonEmpty: Bool { return !self.isEmpty }
>  }
> 
>  if !string.isEmpty { … }
> 
>  if string.isEmpty.inverted() { … }
> 
>  if string.nonEmpty { … }
> 
> For the case of `contains`, maybe define `lacks`?
> 
>  if !items.contains(item) { ... }
> 
>  if items.contains(item).inverted() { ... }
> 
>  if items.lacks(item) { ... }
> 
> Anders Kierulf
> 
>> On Jan 12, 2018, at 12:54 PM, Alejandro Martinez via swift-evolution <swift-evolution at swift.org> wrote:
>> 
>> I wouldn't go as far as to ask to fade out ! but in all my code I end
>> up doing == false just for readability. That ! knows who to hide
>> himself too well :P
>> 
>> On Fri, Jan 12, 2018 at 10:13 AM, Adrian Zubarev via swift-evolution
>> <swift-evolution at swift.org> wrote:
>>> I’m not sure if this would be considered or not, but I would like if the
>>> negation operator `!` would fade out.
>>> 
>>> If this is ever going to a review then I’d suggest that we add a pair of
>>> functions, one mutating and the other non-mutating.
>>> 
>>> extension Bool {
>>> mutating func invert() {
>>>   self = !self
>>> }
>>> 
>>> func inverted() {
>>>   return !self
>>> }
>>> }
>>> 
>>> I’d rather use `inverted` instead of `!` because of the readability this
>>> function provides.
>>> 
>>> if !items.contains(item) { ... }
>>> 
>>> if items.contains(item).inverted() { ... }
>>> 
>>> ——
>>> 
>>> I personally have some other extensions like:
>>> 
>>> extension Bool {
>>> @discardableResult
>>> func whenTrue<T>(execute closure: () throws -> T) rethrows -> T? {
>>>   if self { return try closure() }
>>>   return nil
>>> }
>>> 
>>> @discardableResult
>>> func whenFalse<T>(execute closure: () throws -> T) rethrows -> T? {
>>>   if !self { return try closure() }
>>>   return nil
>>> }
>>> }
>>> 
>>> But this is more a personal preference.
>>> 
>>> ——
>>> 
>>> That said, if the community is fine with the `invert/inverted` pair then I’d
>>> say go for it ;)
>>> 
>>> Am 12. Januar 2018 um 09:14:22, Nate Cook via swift-evolution
>>> (swift-evolution at swift.org) schrieb:
>>> 
>>> 
>>> On Jan 12, 2018, at 12:15 AM, Chris Eidhof via swift-evolution
>>> <swift-evolution at swift.org> wrote:
>>> 
>>> Hey SE!
>>> 
>>> When we have a bunch of nested structs:
>>> 
>>>   struct Sample {
>>>       var bar: Bar
>>>   }
>>> 
>>>   struct Bar {
>>>       var show: Bool
>>>   }
>>> 
>>>   var foo = Sample(bar: Bar(show: false))
>>> 
>>> It can be repetitive to toggle a deeply nested boolean:
>>> 
>>>   foo.bar.show = !foo.bar.show // duplication
>>> 
>>> I sometimes add a `toggle` extension on `Bool`
>>> 
>>>   extension Bool {
>>>       mutating func toggle() {
>>>           self = !self
>>>       }
>>>   }
>>> 
>>> This allows you to write the same code without duplication, and makes the
>>> intent clearer:
>>> 
>>>   foo.bar.show.toggle()
>>> 
>>> 
>>> I like it!
>>> 
>>> In other languages, I don't think the `toggle` would make as much sense, but
>>> the mutable self makes this very useful.
>>> 
>>> After I posted it on Twitter, it turns out I'm not the only one:
>>> https://twitter.com/PublicExtension/status/730434956376346624
>>> 
>>> I would have gone straight to a proposal, but I think we can do some
>>> bikeshedding about the name of `toggle`?
>>> 
>>> 
>>> Another verb that could work is `invert`.
>>> 
>>> The `!` operator that does this is the negation operator, but I think
>>> `negate` could sound to some like "make this false" rather than toggling.
>>> 
>>> Nate
>>> _______________________________________________
>>> swift-evolution mailing list
>>> swift-evolution at swift.org
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>> 
>>> 
>>> _______________________________________________
>>> swift-evolution mailing list
>>> swift-evolution at swift.org
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>> 
>> 
>> 
>> 
>> -- 
>> Alejandro Martinez
>> http://alejandromp.com
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
> 
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20180113/c1d23667/attachment.html>