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

[C. Keith Ray]

(I know isTrue is redundant. I only considered it for symmetry.)

> On Jan 13, 2018, at 11:09 AM, C. Keith Ray <keithray at mac.com> wrote:
> 
> If you would like something better than "== false" I suggest adding computed properties 'isTrue' and 'isFalse' to Boolean.
> 
> 
>> On Jan 13, 2018, at 11:06 AM, Karl Wagner via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> 
>> 
>>> On 12. Jan 2018, at 20:54, Alejandro Martinez via swift-evolution <swift-evolution at swift.org <mailto: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
>>> 
>> 
>> Yeah so do I. ! is a very narrow character and totally changes the meaning of the logic.
>> 
>> That said, I can’t come up with a clearer name than “== false”. inverted() isn’t helpful. toggle() on a mutable Bool is good, though.
>> 
>> - Karl
>> 
>>> On Fri, Jan 12, 2018 at 10:13 AM, Adrian Zubarev via swift-evolution
>>> <swift-evolution at swift.org <mailto: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 <mailto:swift-evolution at swift.org>) schrieb:
>>>> 
>>>> 
>>>> On Jan 12, 2018, at 12:15 AM, Chris Eidhof via swift-evolution
>>>> <swift-evolution at swift.org <mailto: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 <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
>>>> 
>>>> 
>>>> _______________________________________________
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>>>> 
>>> 
>>> 
>>> 
>>> -- 
>>> Alejandro Martinez
>>> http://alejandromp.com <http://alejandromp.com/>
>>> _______________________________________________
>>> swift-evolution mailing list
>>> swift-evolution at swift.org
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>> 
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