[swift-evolution] TrigonometricFloatingPoint/MathFloatingPoint protocol?

Stephen Canon scanon at apple.com
Thu Aug 3 05:59:57 CDT 2017


> On Aug 2, 2017, at 6:37 PM, Nicolas Fezans via swift-evolution <swift-evolution at swift.org> wrote:
> 
> I am of course not talking about a syntax sugar to call a sin or cos function, but rather to manipulate other objects such as N-dimensional matrices, defining maths functions that can take such matrices as argument e.g. sin(A) with A as matrix produces a matrix of the same size where all elements are the sinus values of the elements of A (sorry but things like this calling map() with 'sin' looks quite ugly for scientists).


You’re on very shaky ground here. It is not at all obvious that sin(A) should be the “elementwise” sine that you suggest, and not the matrix sine (defined by plugging A into the power series for sine, which is globally convergent). Depending on what branch of science/math you come from, one of these is “obviously” the right answer, but I assure you that it’s very much not obvious.

Yes, we want libraries to build this sort of thing to exist.

No, it’s not clear what the “right” way to expose some of these operations in the language/library are.

It is better to be verbose but correct than to be terse and cause bugs.

– Steve
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