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

[Alejandro Martinez]

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
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-- 
Alejandro Martinez
http://alejandromp.com