[swift-evolution] [swift-evolution-announce] [Review] SE-0067: Enhanced Floating Point Protocols

[Xiaodi Wu]

If this design is a workaround for type checker limitations, then perhaps
comparison method names are better prefixed with an underscore and/or using
abbreviated terms-of-art (eq, lt, lte, etc.)? As Tony points out, it seems
tragic to promote to an equal footing with `2.0 + 2.0 == 4.0` the
alternative form `(2.0).adding(2.0).isEqual(to: 4.0)`.

On Tue, Apr 26, 2016 at 13:44 Chris Lattner via swift-evolution <
swift-evolution at swift.org> wrote:

>
> > On Apr 26, 2016, at 11:42 AM, Chris Lattner via swift-evolution <
> swift-evolution at swift.org> wrote:
> >
> > On Apr 26, 2016, at 8:47 AM, Tony Allevato via swift-evolution <
> swift-evolution at swift.org> wrote:
> >> That seems like a purely syntactic concern that could potentially be
> addressed in other ways, though. I'm not sure the choice of "duplicate all
> operators using verbosely-named methods" is the best one for the reasons I
> mentioned above, and the question of "how do we cleanly unify operators
> with other protocol requirements?" seems out-of-scope and orthogonal to
> this proposal.
> >
> > There is a strong motivation for this approach though: we want the type
> checker to be scalable.  John recently wrote an epic piece about why having
> tons of overloads is a really bad idea:
> >
> https://lists.swift.org/pipermail/swift-dev/Week-of-Mon-20160404/001650.html
> >
> > It is *much* better for type checker performance to have (e.g.):
> >
> > func +<T : FloatingPoint>(lhs : T, rhs : T) -> T { return lhs.add(rhs) }
> > func +<T : Integer>(lhs : T, rhs : T) -> T { return lhs.add(rhs) }
> >
> > Rather than overloads for 4 floating point types, and 8+ integer types.
>  We really need to eliminate all the “expression too complex” classes of
> issues, and this is an important cause of them.
>
> Also, sorry for not being explicit about this.  I’m not a type checker
> expert, but I believe that using operator requirements imposes the same
> load on the type checker as having large overload sets.
>
> -Chris
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