[swift-evolution] [Pitch] Replace 'inout' with '&'

[Matthew Johnson]

> On Dec 21, 2015, at 12:36 PM, Dmitri Gribenko via swift-evolution <swift-evolution at swift.org> wrote:
> 
> On Mon, Dec 21, 2015 at 10:34 AM, Joe Groff <jgroff at apple.com> wrote:
>> 
>>> On Dec 18, 2015, at 6:52 PM, Dmitri Gribenko <gribozavr at gmail.com> wrote:
>>> 
>>> On Fri, Dec 18, 2015 at 6:21 PM, Joe Groff <jgroff at apple.com> wrote:
>>>> 
>>>> On Dec 18, 2015, at 6:08 PM, Dmitri Gribenko <gribozavr at gmail.com> wrote:
>>>> There's also a possibility that we add 'out' parameters in the future, and
>>>> if 'inout' would be spelled '&', then we would need to find another sigil
>>>> for 'out'.
>>>> 
>>>> We have multiple returns. Why would we ever add out parameters?
>>> 
>>> I don't want to turn this thread into a discussion about out
>>> parameters, but one reason would be to replace
>>> AutoreleasingUnsafeMutablePointer.
>> 
>> IMO we should eventually import out params from C as multiple returns.
>> 
>>> Another one is to add labels to
>>> the output parameters:
>>> 
>>> let (day, month, year) = parseDate()
>>> let (year, day, month) = parseDate() // bug?
>> 
>> Labeled tuples seem like they could help with that, with compiler QoI to catch cases like this where you obviously permuted the return names.
> 
> Currently they don't help:
> 
> (swift) func parseDate() -> (day: Int, month: Int, year: Int) { return (0,0,0) }
> (swift) let (year, month, day) = parseDate()
> // (year, month, day) : (Int, Int, Int) = (0, 0, 0)


Looks like they help to me:

func labeledMultiReturn() -> (string: String, int: Int) {
    return (string: "hello", int: 42)
}

let (string: boundString, int: boundInt) = labeledMultiReturn()

print(boundString)
print(boundInt)

> 
> Dmitri
> 
> -- 
> main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if
> (j){printf("%d\n",i);}}} /*Dmitri Gribenko <gribozavr at gmail.com>*/
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