It's a poster child for a 'let' expression instead of twisting instanceof to
work with no type
return let results = multiResolve(false) in results.length == 1 &&
results[0].isValidResult() ? results[0].getElement() : null;
Rémi
----- Mail original -----
> De: "Brian Goetz" <brian.go...@oracle.com>
> À: "Tagir Valeev" <amae...@gmail.com>
> Cc: "amber-spec-experts" <amber-spec-experts@openjdk.java.net>
> Envoyé: Lundi 4 Mars 2019 08:34:46
> Objet: Re: Patterns for arrays of specific length
> In general, there’s a duality between the ways in which we construct
> composites
> and the way we deconstruct them. There’s an obvious duality between
> constructor and deconstructor patterns; between static factories and static
> patterns, etc.
>
> For structural composites, the obvious place to start is the dual of
> array/list/map literals. (We’re not ready to do these just yet, but it makes
> sense that we consider structural literals and structural patterns at the same
> time.) So for example, if an array literal looks like [ e, f, g ], an array
> pattern might look like [ p, q, r ].
>
> Given that, your example might look like:
>
> return resolveResults instanceof [ var e ] && e.isValid() ? e : null
>
> Without collection literals, we’d write methods to do what we want, so these
> methods have duals too. For example:
>
> return resolveResults instanceof oneElementArray(var e) && e.isvalid() ? e
> :
> null
>
>
>
>
>> On Mar 4, 2019, at 3:30 AM, Tagir Valeev <amae...@gmail.com> wrote:
>>
>> Hello!
>>
>> In intellij IDEA code we often see snippets like this:
>>
>> final ResolveResult[] resolveResults = multiResolve(false);
>> return resolveResults.length == 1 && resolveResults[0].isValidResult() ?
>> resolveResults[0].getElement() : null;
>>
>> I wonder if special kind of patterns to cover such case could be invented
>> like
>>
>> return multiResolve(false) instanceof ResolveResult[] {var res} &&
>> res.isValidResult() ?
>> res.getElement() : null;
>>
>> In essence it should be a deconstruction pattern for arrays. I don't
>> remember whether it was discussed, but probably I'm missing something.
>>
>> Alternatively this could be covered by utility method like
>>
>> static <T> T getOnlyElement(T[] array) {
>> return array.length == 1 ? array[0] : null;
>> }
>>
>> return getOnlyElement(multiResolve(false)) instanceof ResolveResult
>> res && res.isValidResult() ?
>> res.getElement() : null;
>>
>> But this doesn't scale for arrays of bigger length.
>>
>> With best regards,
> > Tagir Valeev.
