[swift-evolution] ternary operator ?: suggestion

[David Waite]

Of course one could just drop it as a grammatical language feature and turn it a standard library feature of some form, e.g.:

@warn_unused_result
func when<T>(@autoclosure expr: ()->Bool, @autoclosure value: ()->T, @autoclosure otherwise: ()->T) -> T {
  if expr() {
    return value()
  }
  else {
    return otherwise()
  }
}

var a = when(1 + 1 == 2, value: "works", otherwise: "fails")

print(a) // => “works"

-DW

> On Dec 4, 2015, at 12:26 AM, David Hart <david at hartbit.com> wrote:
> 
> I also tend to agree but I don't like the ordering in the Python version and would rather see the introduction of the then keyword
> 
> On 04 Dec 2015, at 06:08, Sean Heber <sean at fifthace.com <mailto:sean at fifthace.com>> wrote:
> 
>> I agree that using ? for ternary feels.. uncomfortable in Swift. I wouldn't mind seeing Python-style or just eliminating it entirely in favor of simplicity.
>> 
>> l8r
>> Sean
>> 
>> On Dec 3, 2015, at 10:48 PM, Dan Appel <dan.appel00 at gmail.com <mailto:dan.appel00 at gmail.com>> wrote:
>> 
>>> I agree that ternary can make code unreadable, especially so with the ‘?’. I personally like the Haskel option the most, but it introduces a new keyword ‘then’, which isn’t great either. Python’s "y if x else z" is therefore, in my opinion, the best alternative.
>>> 
>>> Also, I found it interesting how split the Rust community was about removing the ternary operator.
>>> 
>>> — 
>>> Dan Appel
>>> 
>>> On Thu, Dec 3, 2015 at 7:58 PM J. Cheyo Jimenez <cheyo at masters3d.com <mailto:cheyo at masters3d.com>> wrote:
>>> Would you consider replacing the C style ?: ternary operator to something that does not use the question mark and colon ? 
>>> 
>>> The use of "?" can be confusing when speed reading code with optionals. 
>>> 
>>> Consider this code as somebody learning swift as their first language.
>>> let result = !condition ? 1 : 2
>>> 
>>> 
>>> Some alternatives:
>>> 
>>> Haskel 
>>> if predicate then expr1 else expr2
>>> Python
>>> result = x if a > b else y
>>> The advantage of not using the question mark is that the language will be more consistency on the use of "?" to mean only optionals. 
>>> 
>>> 
>>> References:
>>> https://devforums.apple.com/message/1020139#1020139 <https://devforums.apple.com/message/1020139#1020139>
>>> https://github.com/rust-lang/rust/issues/1698#issuecomment-3705066 <https://github.com/rust-lang/rust/issues/1698#issuecomment-3705066> _______________________________________________
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