[swift-evolution] repeat loop enhancement

[Eli Hini]

+1 

Sent from my iPhone

> On Dec 8, 2015, at 21:10, Kenny Leung via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Why don’t you just do
> 
> for x in 1...5 {
>    … some code...
> }
> 
> If you’re teaching to newcomers:
> 
> - there’s no need to explain that counting starts at 0 because it doesn’t
> - if “x” is not used within the loop, then they will get a warning. That would be the perfect time to explain that they can just replace index with “_” when you don’t need to use the value within the loop.
> 
> BTW, I hate the “in x ..< count” syntax. If you mean count from 0 to 4, then just write 0…4
> 
> -Kenny
> 
> 
> Excerpt From: Apple Inc. “The Swift Programming Language (Swift 2 Prerelease).” iBooks. 
> 
>> On 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-
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> 
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