[swift-evolution] TrigonometricFloatingPoint/MathFloatingPoint protocol?

Karl Wagner razielim at gmail.com
Thu Aug 3 18:11:54 CDT 2017

> On 3. Aug 2017, at 13:04, Stephen Canon via swift-evolution <swift-evolution at swift.org> wrote:
>> On Aug 2, 2017, at 7:03 PM, Karl Wagner via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> It’s important to remember that computers are mathematical machines, and some functions which are implemented in hardware on essentially every platform (like sin/cos/etc) are definitely best implemented as compiler intrinsics.
> sin/cos/etc are implemented in software, not hardware. x86 does have the FSIN/FCOS instructions, but (almost) no one actually uses them to implement the sin( ) and cos( ) functions; they are a legacy curiosity, both too slow and too inaccurate for serious use today. There are no analogous instructions on ARM or PPC.
> – Steve
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Hah that’s pretty cool; I think I learned in EE years ago that it was implemented with a lookup table inside the CPU and never bothered to question it.

The pure-Swift cosine implementation looks cool.

As for the larger discussion about a Swift maths library: in general, it’s hard for any new Swift-only package to get off the ground without a more comprehensive package manager. The current version doesn’t support most of the Swift projects being worked on every day. Swift is also still a relatively young language - the new integer protocols have never even shipped in a stable release. Considering where we are, it’s not really surprising that most of the Swift maths libraries are still a bit rudimentary; I expect they will naturally evolve and develop in time, the way open-source code does.

It’s also worth considering that our excellent bridging with C removes some of the impetus to rewrite all your battle-tested maths code in Swift. The benefits are not obvious; the stage is set for pioneers to experiment and show the world why they should be writing their maths code in Swift.

- Karl
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