[swift-evolution] [Review] SE-0159: Fix Private Access Levels

Xiaodi Wu xiaodi.wu at gmail.com
Fri Mar 24 22:28:30 CDT 2017


I'm not sure where you're reading that Chris thinks the current design
reaches the stated aims to his satisfaction.

Again, I agree with the stated design goals for static/dynamic dispatch,
but I don't think they've been met.
On Fri, Mar 24, 2017 at 22:23 Drew Crawford <drew at sealedabstract.com> wrote:

>
>
>
> On March 24, 2017 at 10:11:07 PM, Xiaodi Wu (xiaodi.wu at gmail.com) wrote:
>
> I agree absolutely with those aims: very predictable performance,
> expressive and clean model, simplified learning and common cases. I'm
> arguing that the giant table of dispatch rules (see:
> http://raizlabscom-wpengine.netdna-ssl.com/dev/wp-content/uploads/sites/10/2016/12/Summary-3.png) does
> not reach that goal.
>
> But clattner believes it does.  This is clearer in his original, which is
> why I quoted it:
>
> predictable performance model (someone writing a bootloader or firmware
> can stick to using Swift structs and have a simple guarantee of no dynamic
> overhead or runtime dependence)
>
> ("predictable performance" to clattner means "value types are direct")
>
> while also providing an expressive and clean high level programming model
> - simplifying learning and the common case where programmers don’t care to
> count cycles.
>
> ("simplifying the learning" to clattner means that the programming model
> appears dynamic and the real performance characteristic is hidden.)
>
> We know (because clattner told us here) what the design goal of Swift is
> with respect to static/dynamic dispatch.  You may not agree with it, but
> that is another issue.
>
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