[swift-evolution] Add an ifPresent function to Optional

[Howard Lovatt]

I don't think:

let a: [Int]? = [1,2,3]

for x in a {
  // a is [1,2,3], not the expected iteration of 1 through 3
}

Is confusing because the type inside the loop is array. You would quickly
pick that you needed two loops:

for xs in a {
  for x in xs {
    // process x: Int
  }
}

On Sunday, 13 March 2016, Kevin Lundberg via swift-evolution <
swift-evolution at swift.org
<javascript:_e(%7B%7D,'cvml','swift-evolution at swift.org');>> wrote:

>
> > +1 -- I've used the "an optional is a collection with max 1 element"
> rhetoric to explain map/flatMap, would be great if this was true instead of
> "morally true".
>
> If optional were a sequence or collection, then could if let be considered
> a special case for this?:
>
> for x in optionalX {
> //...
> }
>
> I do like the idea that optional could be considered a collection, but I
> also worry about confusion in this case:
>
> let a: [Int]? = [1,2,3]
>
> for x in a {
>   // a is [1,2,3], not the expected iteration of 1 through 3
> }
>
> Today this does not compile and you are forced to unwrap the optional
> somehow. With this change I can see that someone may unexpectedly try this
> and be confused as to why the type of x is not what they expect.
>
> >> @Dave,Yes, CollectionType would be better than SequenceType.
> >>
> >> On Saturday, 12 March 2016, Dave via swift-evolution<
> swift-evolution at swift.org(mailto:swift-evolution at swift.org)>wrote:
> >> > +1.
> >> >
> >> > I’d go so far as to suggest that maybe Optional should conform to
> CollectionProtocol, since you can pretty easily think of an Optional as a
> collection that can’t have more than one element.
> >> >
> >> > - Dave Sweeris
> >> >
> >> > > On Mar 10, 2016, at 7:32 PM, Erica Sadun via swift-evolution<
> swift-evolution at swift.org(javascript:_e(%7B%7D,'cvml','
> swift-evolution at swift.org');)>wrote:
> >> > >
> >> > > While I'm not convinced of the utility or lack thereof, wouldn't it
> make more sense
> >> > > to extend `forEach` to support optionals in a similar way that map
> and flapMap
> >> > > currently do rather than introduce `ifPresent`?
> >> > >
> >> > > lety:Int? =1
> >> > > letn:Int? =nil
> >> > >
> >> > > _=y.map({print($0) }) // works in current Swift
> >> > > _=n.map({print($0) }) // ditto
> >> > >
> >> > >
> >> > > y.forEach{ print($0) } // not currently a thing
> >> > > n.forEach{ print($0) } // ditto
> >> > >
> >> > > Just spitballing here.
> >> > >
> >> > > -- E
> >> > >
> >> > > _______________________________________________
> >> > > swift-evolution mailing list
> >> > > swift-evolution at swift.org(javascript:_e(%7B%7D,'cvml','
> swift-evolution at swift.org');)
> >> > > https://lists.swift.org/mailman/listinfo/swift-evolution
> >> --
> >> -- Howard.
> > _______________________________________________
> > swift-evolution mailing list
> > swift-evolution at swift.org
> > https://lists.swift.org/mailman/listinfo/swift-evolution
>
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-- 
-- Howard.
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