[swift-evolution] Int indexing into UTF16View

[Félix Cloutier]

It's not. Static strings use UTF-8.

> Le 8 juin 2017 à 16:38, David Hart via swift-evolution <swift-evolution at swift.org> a écrit :
> 
> 
> 
>> On 8 Jun 2017, at 14:15, Vladimir.S <svabox at gmail.com> wrote:
>> 
>>> On 08.06.2017 20:32, David Hart via swift-evolution wrote:
>>> Hello,
>>> When working with Strings which are known to be ASCII, I tend to use the UTF16View for the performance of random access. 
>> 
>> About the performance. Do we have a guarantee that 'barcode' declared in code and/or containing only ASCII chars internally stored as UTF16 ? Otherwise, as I understand, you'll have a performance penalty calling utf16 when internal storage is in UTF8 for example, no?
> 
> I'm fairly sure the internal storage of String is always UTF16.
> 
>> I would also like to have the convenience of indexing with Int:
>>> let barcode = "M1XXXXXXXXX/CLEMENT   EELT9QBQGVAAMSEZY1353 244 21D 531  10A1311446838”
>>> let name = barcode.utf16[2..<22]
>>> let pnrCode = barcode.utf16[23..<30]
>>> let seatNo = barcode.utf16[47..<51]
>>> let fromCity = barcode.utf16[30..<33]
>>> let toCity = barcode.utf16[33..<36]
>>> let carrier = barcode.utf16[36..<39]
>>> let flightNumber = barcode.utf16[39..<44]
>>> let day = barcode.utf16[44..<47]
>>> I define my own subscript in an extension to UTF16View but I think this should go in the Standard Library.
>>> Any thoughts?
>>> David.
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