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

[Amir Michail]

> On Dec 12, 2015, at 11:28 AM, Al Skipp via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Top marks!
> 
> unless(condition) { print("condition was false") }

Implicitly negated conditions cause confusion and bugs.

> 
> The feature implemented in the language. What’s not to like?
> 
>> On 12 Dec 2015, at 16:20, Tommy van der Vorst via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> Oops, that should be just:
>> 
>> public func unless(expression: Bool, block: () -> ()) {
>> 	if !expression {
>> 		block()
>> 	}
>> }
>> 
>>> Op 12 dec. 2015, om 17:17 heeft Tommy van der Vorst via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> het volgende geschreven:
>>> 
>>> Or, use something like this:
>>> 
>>> public func unless(expression: @autoclosure () -> Bool, block: () -> ()) {
>>> 	if !expression {
>>> 		block()
>>> 	}
>>> }
>>> 
>>> unless(..expression..) { 
>>> 	...code...
>>> }
>>> 
>>> /T
>>> 
>>>> Op 12 dec. 2015, om 17:08 heeft Al Skipp via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> het volgende geschreven:
>>>> 
>>>> 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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>>>>>> 
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>>>>> 
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