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

[C. Keith Ray]

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> 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> 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
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>>> swift-evolution at swift.org
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>>> 
>>> 
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>>> 
>> 
>> 
>> 
>> -- 
>> Alejandro Martinez
>> http://alejandromp.com
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> 
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