[swift-evolution] Add unless/if single line syntax

[Matthew Johnson]

I’ve written enough Ruby code to appreciate these keywords and believe they are worth adding the keywords.  I know others don’t agree and that the Swift team considered this earlier and did not add them for the exact reason you stated.  

I think it would be good to get a read on where the community stands.  I’m not sure which opinion is in the majority.

> On Dec 12, 2015, at 10:08 AM, Al Skipp <al_skipp at fastmail.fm> wrote:
> 
> If at all possible I think it’s best to avoid adding keywords to the language. Instead of ‘unless', you could do: 
> 
> public func not(bool: Bool) -> Bool { return !bool }
> 
> if not(condition) { print("condition was false") }
> 
> Not terrible ¯\_(ツ)_/¯
> 
> 
>> On 12 Dec 2015, at 15:48, Matthew Johnson via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> I’m not sure about the single line aspect of this proposal, but I am a big proponent of “unless” and “until” as complements to “if” and “while”.  They greatly improve readability over "if !(expression)” and “while !(expression)” IMHO.
>> 
>>> On Dec 12, 2015, at 9:45 AM, Arthur Ariel Sabintsev via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>> For your specific example, I'd 100% use the guard statement. It achieves the same result.
>>> 
>>> -1 from me.
>>> On Sat, Dec 12, 2015 at 9:43 AM J. Cheyo Jimenez via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> -1 from me.  I think I would rather have an if-then expression that would handle both False and True cases. 
>>> https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20151207/001944.html <https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20151207/001944.html>
>>> 
>>> Also, in most cases I feel that guard would be a better choice. 
>>> 
>>> 
>>> 
>>> On Sat, Dec 12, 2015 at 5:39 AM, James Campbell via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> I propose adding the unless and if statements from ruby.
>>> 
>>> Return false if james = nil
>>> 
>>> This returns false if the variable James is nil
>>> . This line does it unless james is nil:
>>> 
>>> Return false unless james = nil
>>> 
>>> This has been really handy when working in ruby, reduces lines and pyramids of doom
>>> 
>>> Sent from my iPhone
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