[swift-evolution] Int indexing into UTF16View

[Vladimir.S]

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 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.
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
>