[swift-evolution] Control Flow Expressions

[J. Cheyo Jimenez]

Never mind, that would not work for returning from a function.

On Monday, December 7, 2015, J. Cheyo Jimenez <cheyo at masters3d.com> wrote:

> 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
> <javascript:_e(%7B%7D,'cvml','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> wrote:
>>
>>
>> On Dec 6, 2015, at 12:17 PM, Per Melin <p at greendale.se> wrote:
>>
>> On Sat, Dec 5, 2015 at 7:15 PM, Chris Lattner <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
>>
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>>
>>
>>
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