"it"? "#"? ""?

[Matthew Adams]

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

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