[swift-evolution] Using "where" to filter an array

[Jacob Bandes-Storch]

It doesn't bother me, because I read it as an additional constraint on the
`for` loop rather than an operation being done on the enumerated sequence.
That is,

    for x in y where x > 2 { }

is fairly consistent with

    if let x = y where x > 2 { }

And you wouldn't expect to be able to do "let x = y where x > 2".

Jacob Bandes-Storch

On Sat, Dec 19, 2015 at 8:22 PM, Charles Constant via swift-evolution <
swift-evolution at swift.org> wrote:

> Thanks Charles ,
>
> I know it's possible to do the same thing with filter. The syntax I drew
> attention to would be an alternate way.
>
> My only rationale is that, if it works in one place, it ought to work
> everywhere. The redundancy bothers me too, but since the concept exists, we
> may as well allow it everywhere. Otherwise, it's still redundant in a "for"
> loop (maybe performance is better, but that could be optimized?), but also
> inconsistent because it seems intuitively like it ought to create a subset
> whereas in reality it is illegal.
>
> Does it bother anyone else, or am I nitpicking?
>
> On Sat, Dec 19, 2015 at 7:52 PM, Charles Srstka <cocoadev at charlessoft.com>
> wrote:
>
>> On Dec 19, 2015, at 9:43 PM, Charles Constant via swift-evolution <
>> swift-evolution at swift.org> wrote:
>>
>>
>> I noticed several weeks ago that the following is illegal:
>>
>>     let new_arr = el in arr where el.is_foo // illegal
>>
>> I assumed it would work because it's consistent with the filtering that
>> exists in a "for" loop, i.e.:
>>
>>     for el in arr where el.is_foo // legal
>>
>> Is this "new proposal" material? I thought I would check in case it's
>> already on the roadmap, or inherently wrong.
>>
>>
>> I believe what you want is already possible via the “filter” method.
>>
>> Charles
>>
>>
>
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