[swift-evolution] [swift-evolution-announce] [Review] SE-0067: Enhanced Floating Point Protocols
allevato at google.com
Tue Apr 26 09:28:49 CDT 2016
On Sun, Apr 24, 2016 at 2:57 AM Nicola Salmoria via swift-evolution <
swift-evolution at swift.org> wrote:
> > > func isEqual(to other: Self) ->Bool
> > > func isLess(than other: Self) ->Bool
> > > func isLessThanOrEqual(to other: Self) ->Bool
> > I'm still not sure why these are methods instead of operators.
> I think this is an *excellent* choice, and I hope it is the first step to
> completely removing operators from protocols.
> IMHO throwing operators into protocols is inconsistent and confusing.
> Having regular methods and a single generic version of the operator that
> calls down on the type’s methods is clearer and guarantees that generic
> code can avoid ambiguities by calling the methods directly, instead of
> having to rely only on heavily overloaded global operators.
I personally disagree on this point. To me, a protocol describes a set of
requirements for a type to fulfill, which includes things other than
methods. Just as a protocol can define initializers, properties, and
associated types that a type must define in order to conform, it makes
sense that a protocol would also define which operators a conforming type
Introducing a mapping between names and operators poses a few problems:
– IMO, they are overly verbose and add noise to the definition. This makes
the language look less clean (I'm getting visions of NSDecimalNumber).
– They expose two ways to accomplish the same thing (writing `x.isEqual(to:
y)` and `x == y`).
– Do certain operators automatically get mapped to method names with
appropriate signatures across all types, or does a conforming type still
have to provide that mapping by implementing the operators separately? If
it's the latter, that's extra work for the author of the type writing the
protocol. If it's the former, does it make sense to automatically push
these operators for all types? Should any type that has an `add` method
automatically get `+` as a synonym as well? That may not be desirable.
I'm very supportive of the floating-point protocol proposal in general, but
I feel the arithmetic and comparison operations should be exposed by
operators alone and not by methods, where there is a suitable operator that
has the intended meaning.
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