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

[Adrian Zubarev]

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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