[swift-evolution] Pitch: Renaming CharacterSet to UnicodeScalarSet

[Xiaodi Wu]

On Wed, Sep 28, 2016 at 10:23 PM, Charles Srstka via swift-evolution <
swift-evolution at swift.org> wrote:

> On Sep 28, 2016, at 9:57 PM, Erica Sadun via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>
> D'erp. I missed that. And that's an unambiguous answer.
>
> So let me move on to part B of the pitch: I think CharacterSets are broken.
>
> Xiaodi Wu: "isn't the problem you're presenting really an argument that
> the type should be fleshed out to handle characters (grapheme clusters)
> containing more than one Unicode scalar?"
>
>
> It seems that it already does handle such characters:
>
> (done in Objective-C so we can log the length of the range as a count of
> UTF-16 code units)
>
> #import <Foundation/Foundation.h>
>
> int main(int argc, char *argv[]) {
>     @autoreleasepool {
>         NSCharacterSet *bikeSet = [NSCharacterSet
> characterSetWithCharactersInString:@"🚲"];
>         NSString *str = @"foo🚲bar";
>
>
>         NSRange range = [str rangeOfCharacterFromSet:bikeSet];
>
>
>         NSLog(@"location: %lu length: %lu", range.location, range.length);
>     }
> }
>
> - - - - - - -
>
> *2016-09-28 22:20:00.622471 test[15577:2433912] location: 3 length: 2*
> *Program ended with exit code: 0*
>
> - - - - - - -
>
> As we can see, the character from the set is recognized as consisting of
> two code units. There are a few bugs in the system, though. See the
> cocoa-dev thread “Where is my bicycle?” from about a year ago:
> http://prod.lists.apple.com/archives/cocoa-dev/2015/Apr/msg00074.html
>

The bike emoji might be two code units, but it is one Unicode scalar
(U+1F6B2). However, the Canadian flag emoji, for instance, is two Unicode
scalars (U+1F1E8 U+1F1E6) but nonetheless one character.

Charles
>
>
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