[swift-dev] [stdlib] Array.description calls debugDescription on its contents

[Dmitri Gribenko]

On Fri, Dec 11, 2015 at 1:38 PM, Wojciech Czekalski via swift-dev <
swift-dev at swift.org> wrote:

> Hi,
>
> while I was working on this <https://github.com/apple/swift/pull/348> PR
> I encountered unexpected behavior from Array.description. It iterates
> over its items and calls debugDescription on them. I found it a bit
> unexpected thus my question here. Is it desired behavior? I would expect
> description and debugDescription call respective methods on the contents.
>

Array's description shouldn't be presented to the user in raw form, ever,
so the use case here is debugging.  Thus, it makes sense to present the
debug representation of the elements in both cases.  Consider an array of
strings:

var myArray = [ "", "", "" ]

If we used the regular description, then String(myArray) would be "[ , ,
]", which looks like a library bug.

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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