[swift-users] Provide native Decimal data type

Jens Alfke jens at mooseyard.com
Mon Sep 12 12:26:18 CDT 2016

> On Sep 12, 2016, at 10:10 AM, Teej . via swift-users <swift-users at swift.org> wrote:
> 	…in spite of the CPU’s quirks in handling floating point numbers in a maddening inaccurate manner.

Well, in the CPU’s defense, it’s only inaccurate because the puny humans insist on dividing their currency into fractions of 1/10, which has no exact representation in binary. (Apparently this is an ancient tradition commemorating the number of bony outgrowths on certain extremities of their grotesque meat-bodies.) I could — I mean, the computers could — point out that if we divided our currency units into 7 pieces, our precious decimal numbers would quickly become inaccurate too. :)

> 	Is there any particular reason why we do not have a native Decimal data type for Swift?  

Cocoa’s Foundation framework has an NSDecimalNumber class that provides decimal numbers and arithmetic. The class docs for that include a note that "The Swift overlay to the Foundation framework provides the Decimal structure, which bridges to the NSDecimalNumber class. The Decimalvalue type offers the same functionality as the NSDecimalNumberreference type, and the two can be used interchangeably in Swift code that interacts with Objective-C APIs."

The question is whether this has been ported to the in-progress native Swift foundation library yet. I haven’t checked.

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