[swift-evolution] "with" operator a la O'Caml?

[Daniel Leping]

Ok. I'm positive with some sort of case classes.

+1 here

On Tue, 20 Dec 2016 at 23:02 Derrick Ho via swift-evolution <
swift-evolution at swift.org> wrote:

> Jeremy,
>
> The problem you present is not a mutability problem but rather a cache
> design problem. If your hash value truly is expensive then you only want to
> calculated it when you need to...
>
> struct Person: Hashable
> {
>     var firstName: String {didSet { _hashValue = nil }}
>     var lastName: String {didSet { _hashValue = nil }}
>     private var _hashValue: Int?
>     var hashValue: Int {
>         if _hashValue == nil {
>             _hashValue = firstName ^ lastName // the "expensive hash
> calculation"
>         }
>         return _hashValue!
>     }
> }
>
> In the above implementation the hash value would only calculate the hash
> when firstName or lastName were changed.
>
> However in your example your hash method would calculate a new one every
> time you copy a Person, but mine would not.
>
> On Tue, Dec 20, 2016 at 6:44 AM Martin Waitz via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Am 2016-12-19 20:44, schrieb Erica Sadun via swift-evolution:
>
>
> > https://github.com/apple/swift-evolution/pull/346
>
>
>
>
>
> -1
>
>
> I don't like where this is heading.
>
>
>
>
>
> If you want to introduce method cascading, then have a look at Dart.
>
>
>
>
>
> E.g. the example from the pull request could be something like this:
>
>
>
>
>
>      let questionLabel = UILabel()
>
>
>          ..textAlignment = .Center
>
>
>          ..font = UIFont(name: "DnealianManuscript", size: 72)
>
>
>          ..text = questionText
>
>
>
>
>
> The expression could still work on a mutable struct/class which later
>
>
> becomes
>
>
> immutable by using the `let` assignment.
>
>
>
>
>
> The other example which silently creates a new instance is even worse.
>
>
> If you want to do something like this, then please do it more
>
>
> explicitly.
>
>
> E.g.:
>
>
>
>
>
>      let fewerFoos = foos.clone()
>
>
>          ..remove(at: i)
>
>
>
>
>
> Anyway, all of this is simply syntactic sugar and should wait...
>
>
>
>
>
> --
>
>
> Martin
>
>
> _______________________________________________
>
>
> 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/20161220/02abc0f8/attachment.html>