+1 for trapping unless using &==. In the case of ‘Float?’ we could also map to nil.
This is probably a more appropriate discussion for evolution though... > On Oct 19, 2017, at 9:48 PM, Brent Royal-Gordon via swift-dev > <swift-dev@swift.org> wrote: > >> On Oct 19, 2017, at 4:29 PM, Xiaodi Wu via swift-dev <swift-dev@swift.org >> <mailto:swift-dev@swift.org>> wrote: >> >> D) Must floating-point IEEE-compliant equivalence be spelled `==`? >> >> In my view, this is something open for debate. I see no reason why it cannot >> be migrated to `&==` if it were felt that `==` *must* be a full equivalence >> relation. I believe this is controversial, however. > > I actually got partway through writing up a pitch on this yesterday, but my > opinion is that NaNs are so exceptional, and so prone to misuse, that we > ought to treat them like integer arithmetic overflows: trap when they're > detected, unless you use an `&` variant operator which indicates you know > what you're doing. > > I strongly suspect that, in practice, most float-manipulating code is not > prepared to handle NaN and will not do anything sensible in its presence. For > example, Apple platforms use floating-point types for geometry, color > components, GPS locations, etc. Very little of this code will do anything > sensible in the presence of a NaN. Arguably, it'd be better to exclude them > through the type system, but I don't think that's a realistic possibility—we > would need to have done that in a more source-break-friendly era. But that > doesn't have to mean we're completely stuck. > > -- > Brent Royal-Gordon > Architechies > > _______________________________________________ > swift-dev mailing list > swift-dev@swift.org > https://lists.swift.org/mailman/listinfo/swift-dev
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