No to this pitch, because a percentage can be higher than 100%.

Use NumberFormatter to display a number as a percentage.

Or you could make an NSNumber subclass if you want to enforce an arbitrary rule 
upon numbers.


> On Jan 13, 2018, at 18:26, Jonathan Hull via swift-evolution 
> <> wrote:
> Hi Evolution,
> I was wondering if we would consider adding a percentage type to Swift.  This 
> would be a type with a value between 0 & 1.
> I know we can and do use doubles or floats for this now, but there really is 
> a semantic difference between most parameters that take a value between 0 & 1 
> and those that take any floating point value.  It would be nice to have a 
> type that semantically means that the value is from 0 to 1.
> It could even just wrap a Double for speed (in my own code I wrap a UInt64 
> for decimal accuracy… and to avoid issues around comparisons).
> Thanks,
> Jon
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