"it"? "#"? ""?

[Brian Goetz]

We're pretty satisfied with the degree of syntax reduction we've achieved so far.  You can make things arbitrarily compact, but that's not the goal.  I don't think that horizontal span is our biggest problem any more.  So don't expect any Scala-style wunderbars or Groovy-style it.  




On Nov 19, 2011, at 3:10 PM, John Nilsson wrote:

> Given that the usecase for this is about implicit context i really like the
> last option of just leaving the space before the period unfilled.
> 
> Similarly it would be nice if it worked for all operators: list.filter(>2)
> 
> BR,
> John million
> Den 19 nov 2011 00:51 skrev "Matthew Adams" <matthew at matthewadams.me>:
> 
>> NB:  I'm searching through the archives on this and didn't see anything
>> that directly addressed it.
>> 
>> I just got through the slides at
>> http://blogs.oracle.com/briangoetz/entry/slides_from_devoxx_talk_on
>> and noticed a nice feature inspired by Groovy that was missing from the
>> slide code examples.  I don't know if it's missing from the lambda
>> proposal, though -- I can't tell from the slides.
>> 
>> Groovy defaults the name of a single closure argument to "it".  I think
>> this would be nice to have in JDK8 lambdas, too.
>> 
>> =====
>> // Without "it":
>> void expire(File root, long before) {
>> ...
>> root.listFiles(File p -> p.lastModified() <= before);
>> ...
>> }
>> =====
>> // With "it":
>> void expire(File root, long before) {
>> ...
>> root.listFiles(it.lastModified() <= before);
>> ...
>> }
>> ======
>> 
>> Is this possible to include, or will the grammar require "->" so that
>> "it.lastModified <= before" isn't interpreted by the compiler as a boolean
>> expression?  If that's the case, how about considering "#" (or some other
>> appropriate character) instead of "it"?  That way, the compiler would know
>> implicitly that if it encounters a "#", it *must* be a lambda expression
>> taking a single variable of an inferred type:
>> 
>> =====
>> // With "#":
>> void expire(File root, long before) {
>> ...
>> root.listFiles(#.lastModified() <= before);
>> ...
>> }
>> ======
>> 
>> You could even reduce "it" or "#" to an empty string and just use the "."
>> with no preceding scope.  I don't know if the grammar could support it, but
>> it's interesting.  I'm not sure I like it, but is sure is compact!
>> 
>> =====
>> // With "":
>> void expire(File root, long before) {
>> ...
>> root.listFiles(.lastModified() <= before);
>> ...
>> }
>> ======
>> 
>> Another example:
>> =====
>> // explicit lambda param name
>> Set<Album> favs = albums
>>   .filter(a -> a.tracks.anyMatch(t -> (t.rating >= 4)))
>>   .into(new HashSet<>());
>> =====
>> // "it"
>> Set<Album> favs = albums
>>   .filter(it.tracks.anyMatch(it.rating >= 4)) // 2 its!?!?
>>   .into(new HashSet<>());
>> =====
>> // "#"
>> Set<Album> favs = albums
>>   .filter(#.tracks.anyMatch(#.rating >= 4))
>>   .into(new HashSet<>());
>> =====
>> // ""
>> Set<Album> favs = albums
>>   .filter(.tracks.anyMatch(.rating >= 4))
>>   .into(new HashSet<>());
>> =====
>> 
>> Thoughts?
>> 
>> -matthew
>> 
>> --
>> @matthewadams12
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>> 
>> 
>