"it"? "#"? ""?

[Rémi Forax]

On 11/19/2011 09:45 PM, Brian Goetz wrote:
> 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.

and don't forget that even if

   root.listFiles(it.lastModified()<= before);


is not legal, this snippet is legal because '_' is a legal identifier

   root.listFiles(_ ->  _.lastModified()<= before);


Rémi

>
>
>
>
> 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
>>> mailto:matthew at matthewadams.me
>>> skype:matthewadams12
>>> yahoo:matthewadams
>>> aol:matthewadams12
>>> google-talk:matthewadams12 at gmail.com
>>> msn:matthew at matthewadams.me
>>> http://matthewadams.me
>>> http://www.linkedin.com/in/matthewadams
>>>
>>>
>