[swift-evolution] Custom equality/hash for Sets

Thorsten Seitz tseitz42 at icloud.com
Fri Feb 19 09:13:59 CST 2016

Needing a Set of identical reference objects, i.e. comparing with ===, has come up quite regularly in the projects I have worked on (as well as indexing by identity in a Dictionary). This might be mitigated in Swift due to a more prominent role of value types but I would still expect it to be useful.


> Am 19.02.2016 um 05:39 schrieb Dmitri Gribenko via swift-evolution <swift-evolution at swift.org>:
> On Thu, Feb 18, 2016 at 2:58 PM, Jacob Bandes-Storch via
> swift-evolution <swift-evolution at swift.org> wrote:
>> Would it make sense for the standard library Set to provide variants (or
>> parallel versions of the same data structure) that take custom hashValue/==
>> implementations at init time (functions taking in Elements), rather than
>> relying on Hashable/Comparable protocols?
> It might make sense, but we should keep in mind that doing this will
> prevent inlining of hashValue/== in most cases.
> Dmitri
> -- 
> main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if
> (j){printf("%d\n",i);}}} /*Dmitri Gribenko <gribozavr at gmail.com>*/
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