[swift-evolution] Control Flow Expressions

[J. Cheyo Jimenez]

How about something like this?

let result = if bool return 1 else 2



On Monday, December 7, 2015, Cameron Knight via swift-evolution <
swift-evolution at swift.org> wrote:

> Why not use a keyword? What if, the keyword 'returning' (or something like
> that) was used to specify the control flow behavior.
>
> // Replaces ternary operator
> let paint.color = returning if door.color == .Red { .Black } else {
> door.color }
>
> // Supports additional conditions
> let paint.finish = returning switch paint.color {
> case .Black:
> .Matte
> case .White:
> .Eggshell
> default:
> .Gloss
> }
>
> // Removes ambiguity of single statement behavior
> let ages: [Int] = people.map returning { $0.age }
>
> // Perhaps overreaching a bit
> let label = returning UILabel(frame: CGRect.zero) {
> .text = "Hello World"
> .color = UIColor.red
> }
>
> I think it adds clarity without too much syntax bloat. I haven't thought
> out all the corner cases though, so maybe I'm missing something obvious.
>
> On Dec 6, 2015, at 4:56 PM, Chris Lattner via swift-evolution <
> swift-evolution at swift.org
> <javascript:_e(%7B%7D,'cvml','swift-evolution at swift.org');>> wrote:
>
>
> On Dec 6, 2015, at 12:17 PM, Per Melin <p at greendale.se
> <javascript:_e(%7B%7D,'cvml','p at greendale.se');>> wrote:
>
> On Sat, Dec 5, 2015 at 7:15 PM, Chris Lattner <clattner at apple.com
> <javascript:_e(%7B%7D,'cvml','clattner at apple.com');>> wrote:
>
>> Further, it is important to consider whether the code written using this
>> will actually be *better* than the code written with these things as
>> statements.  For example, the “switch” blocks tend to be very large, and
>> turning them into expressions encourages additional indentation.
>
>
> If you give functions implicit return at the same time – as in Haskell,
> Erlang, Scala, Rust, Ruby, Lisp/Scheme/Clojure, etc –  there would be no
> need for additional indentation half of the time.
>
>
> This isn’t something that I’m personally interested in.  I think that it
> is *feature* of swift that statements an declarations start with keywords.
> This greatly simplifies the grammar in various ways, and allows
> declmodifiers to be introduced without taking keywords space.
>
> For example, relevant to this proposal, if/when we support “tail return
> foo()" for example, you don’t want to take “tail” as a keyword to make
> “tail foo()” work.
>
> Not even Slava Pestov would factor Swift that aggressively.
>
>
> Underestimating Slava is not a good idea! :-)
>
> -Chris
>
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> <javascript:_e(%7B%7D,'cvml','swift-evolution at swift.org');>
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20151207/62231d07/attachment.html>