The functionality of the `where` clause in `for` loops also already can be
mimicked using `filter`. Wouldn’t we have to get ride of the `where` clause by
that logic?
> The functionality being asked for here is already accepted for inclusion to
> Swift as a method on Sequence named `prefix(while:)` (SE-0045):
>
> `for element in array.prefix(while: { someCondition($0) }) { ... }`
> On Mon, Jun 6, 2016 at 14:31 T.J. Usiyan via
> swift-evolution<[email protected](mailto:[email protected])>wrote:
> > (As I said, I can live with `while`. I am simply presenting a potential
> > point of confusion.)
> > You aren't evaluating the statements in the loop 'while' the condition
> > isn't met. The first time that the condition isn't met, evaluation of the
> > loop stops. I get that this is technically true for the `while` construct
> > but I suggest that the only reason that it works there is that 'stopping
> > the first time that the condition isn't met' *is* the construct. Here, we
> > have a loop that we execute for each thing and we're tacking
> > on/intermingling the `while` construct.
> >
> >
> >
> > On Mon, Jun 6, 2016 at 2:19 PM, Thorsten
> > Seitz<[email protected](mailto:[email protected])>wrote:
> > >
> > > >Am 06.06.2016 um 19:43 schrieb Tim Vermeulen via
> > > >swift-evolution<[email protected](mailto:[email protected])>:
> > > >
> > > >I also considered `until`, but it would be a bit confusing that `where`
> > > >makes sure a condition is met, while `until` makes sure the condition
> > > >isn’t met. I think `while` makes more sense because it corresponds to
> > > >`break` in the same way that `where` corresponds to `continue`.
> > >
> > > That's a good argument! The only drawback is that `while` and `where`
> > > look quite similar at a glance.
> > >
> > > -Thorsten
> > >
> > > >
> > > >>`while`, to me, actually reads like it should do what `where` does.
> > > >
> > > >To me, `while` reads like it should stop the loop once the condition
> > > >isn’t met, just like in a while loop.
> > > >
> > > >>I hadn't thought about `while` in this regard but wouldn't `until` make
> > > >>more sense? `while`, to me, actually reads like it should do what
> > > >>`where` does. In any case, whether it is `while` or `where`, this seems
> > > >>like a reasonable feature in my opinion.
> > > >>
> > > >>TJ
> > > >>
> > > >>On Mon, Jun 6, 2016 at 5:15 AM, Tim Vermeulen via
> > > >>swift-evolution<[email protected](mailto:[email protected])(mailto:[email protected])>wrote:
> > > >>>We can already use a where clause in a for loop like this:
> > > >>>
> > > >>>for element in array where someCondition(element) {
> > > >>>// …
> > > >>>}
> > > >>>
> > > >>>which basically acts like
> > > >>>
> > > >>>for element in array {
> > > >>>guard someCondition(element) else { continue }
> > > >>>// …
> > > >>>}
> > > >>>
> > > >>>Sometimes you want to break out of the loop when the condition isn’t
> > > >>>met instead. I propose a while clause:
> > > >>>
> > > >>>for element in array while someCondition(element) {
> > > >>>// …
> > > >>>}
> > > >>>
> > > >>>which would be syntactic sugar for
> > > >>>
> > > >>>for element in array {
> > > >>>guard someCondition(element) else { break }
> > > >>>…
> > > >>>}
> > > >>>
> > > >>>I can see this particularly being useful if we have a sorted array and
> > > >>>we already know that once the condition isn’t met, it won’t be met
> > > >>>either for subsequent elements. Another use case could be an infinite
> > > >>>sequence that we want to cut off somewhere (which is simply not
> > > >>>possible using a where clause).
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