[swift-evolution] [Planning][Request] "constexpr" for Swift 5

Gor Gyolchanyan gor.f.gyolchanyan at icloud.com
Sun Jul 30 12:03:15 CDT 2017

Tino Heth:
If you read my reply to Daniel Vollmer, you’ll find that we’re thinking about the exact same thing. Your code snippers show my vision of compiletime beautifully 🙂.
Now what I really want at this point is to here the opinions of the core team on this topic.

Swift Core Team:
Have you guys thought of this? Do you think this is a good idea to put on the table or do you have different plans?

> On Jul 30, 2017, at 7:56 PM, Tino Heth <2th at gmx.de> wrote:
>> more elaborate compile-time facilities, which would also provide extremely powerful meta programming features
> That's an interesting twist — but whenever you put a "meta" somewhere, things tend to get complicated, and people end up with different associations to the topic… ;-)
> I took a brief look at the C++ document, but it seemed still to much macro-like to me.
> My take on the topic would be he ability to express common programming tasks (declaring a class, overriding a method…) in the language itself.
> Imagine
> public class ProxyViewController: UIView {}
> Could be written as
> let subclass = createClass(classname: "ProxyViewController", superclass: UIViewController, accessLevel: .public)
> Quite stupid at first sight, and basically the exact opposite of syntactic sugar ("syntactic salt" already has a meaning… so I'd call it "syntactic pepper" ;-).
> But now imagine that:
> for (method, implementation) in UIViewController.methods where method.accessLevel == .open {
>     subclass.methods[method] = { parameters in
>         print("Subclass method \(method) called with \(parameters)")
>         return implementation(parameters)
>     }
> }
> Not that stupid anymore, isn't it?
> I think this would be way cooler than poking around with variants of search & replace…
> - Tino
> (to get syntax colouring, I wrote ~30 lines of Swift that turn the straw man example into valid code… it's fun, maybe I play with it a little bit more ;-)

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