[swift-evolution] [swift-evolution-announce] [Re-Review] SE-0104: Protocol-oriented integers

[Xiaodi Wu]

Sign, perhaps, can be thought of as "part of a number," but signum refers
to the signum function (http://en.wikipedia.org/wiki/Sign_function) defined
as:

-1 if x < 0
0 if x = 0
1 if x > 0

1 isn't really "part of" 42, for instance, at least not in the sense that
42 and + are "part of" 42.
On Tue, Feb 21, 2017 at 22:18 Howard Lovatt via swift-evolution <
swift-evolution at swift.org> wrote:

> You raised two points:
>
>   1. "... magnitude is something the number ‘has’ whereas signum is a
> completely new thing ..." I think sign is as much part of a number as
> magnitude. Its a minor point, code complete gets it anyway.
>
>   2. "... [extras] are defined as protocol extensions, therefore they
> should be discoverable through completion ..." I wasn't thinking so much
> about code completion, more browsing the protocol to see what is available
> (I use SwiftDoc quite a bit).
>
> Thanks for running with this - very valuable,
>
>   -- Howard.
>
> On 22 February 2017 at 10:27, Max Moiseev <moiseev at apple.com> wrote:
>
>
> On Feb 21, 2017, at 3:05 PM, Howard Lovatt via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> The re-review of SE-0104 "Protocol-oriented integers" begins now and runs
> through February 25, 2017. This proposal was accepted for Swift 3, but was
> not implemented in time for the release. The revised proposal is available
> here:
>
>
>
> https://github.com/apple/swift-evolution/blob/master/proposals/0104-improved-integers.md
>
>
> • What is your evaluation of the proposal?
>
>
> Well worth while. Few nit picks:
>
>   1. Number.init? Description should say BinaryInteger not floating-point.
>
> I’ll update the proposal.
>
>   2. Number should document that mutating versions of operators can
> overflow.
>   3. SignedNumber should document that negate and unary `-` can overflow.
>
> Documentation changes noted. Thanks!
>
>   4. SignedNumber, it is weird that `signum` is a function when other
> similar things, e.g. `magnitude`, are properties.
>
> I think of it as: magnitude is something the number ‘has’ whereas signum
> is a completely new thing of the same type.
>
>   5. Not worth representing `DoubleWidth` as an enumeration, it is obscure
> and therefore will only confuse people.
>   6. It would be better to put the 'extra' operations into the protocols
> and provide default implementations, otherwise they are difficult to find.
>
> They are defined as protocol extensions, therefore they should be
> discoverable through completion and in the generated source code. Or what
> do you mean by ‘difficult to find’?
>
> Thanks for the feedback!
>
>
> • Is the problem being addressed significant enough to warrant a change to
> Swift?
>
>
> Yes, the current design has not served my purpose on more than one
> occasion
>
>
> • Does this proposal fit well with the feel and direction of Swift?
>
>
> Yes
>
>
> • If you have used other languages or libraries with a similar feature,
> how do you feel that this proposal compares to those?
>
>
> Yes, this proposal is similar to what other languages provide, e.g. Scala.
> In Scala however they tackle the `conversion problem as well in their
> `traits heirarchy. I guess this could be added at a later date.
>
>
> • How much effort did you put into your review? A glance, a quick reading,
> or an in-depth study?
>
>
> Read the proposal, have used similar features in other languages, and have
> had trouble with Swift's current heirarchy.
> --
> -- Howard.
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>
>
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