[swift-evolution] repeat loop enhancement

[Jacob Bandes-Storch]

If the goal is to avoid leaking variables into the outer scope, you might
be happy with something like

repeat var x = 0 {
    // ...
    [update x]
} while [condition that has access to x]

// x is out of scope here

Jacob

On Tue, Dec 8, 2015 at 1:54 PM, Jason Pollack via swift-evolution <
swift-evolution at swift.org> wrote:

> I'd like to propose a small enhancement to the repeat loop.
>
> Currently if we want to perform 'count' iterations in a loop, we need to
> do something like:
>
> for _ in 0 ..< count {
>    //Do something here
> }
>
> It looks and feels a little awkward. We need to create an unnamed
> variable, and it's easy to forget (especially for language newcomers) that
> the loop starts with 0 and doesn't include count.
>
> We can also do:
>
> var i = 0
> repeat {
>     //Some code
>     i += 1
> } while i < 10
>
> This is worse, in that it introduces a variable in the outer scope, and
> puts the repeat count at the end. Plus, if the expression inside the repeat
> is complex, the value of i may never be incremented, or may be incremented
> more than once.
>
>
> I propose the following:
>
> repeat count {
>     //Do something here
> }
>
> It's cleaner, and IMO clearer what this code is intended to do.
>
> Naturally 'count' should be non-negative. A while clause is not needed,
> although I could imagine it being supplied, to create a construct such as:
>
> var ok = true
> repeat numberOfTimes {
>     //Do something, possibly set ok to false
> } while ok
>
> This would repeat the loop a maximum of  'numberOfTimes', but could be
> ended early if some signal 'ok' is set to false (or, of course, by a break
> statement).
>
> Thoughts?
>
> Thanks!
> -Jason-
>
> _______________________________________________
> 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/20151208/8971bda4/attachment.html>