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From David Whiting <d...@apache.org>
Subject Re: Alternative strategy for incorporating Java 8 lambdas into Crunch
Date Fri, 11 Dec 2015 22:17:01 GMT
I *think* you can set language level and target jdk on a per-module basis,
so it should be relatively easy. I'll experiment at some point over the
weekend. Would this complement or replace the I*Fn stuff do you think? 14.0
is not yet released, so I guess it's not too late to change if we want to.

On 11 December 2015 at 22:57, Josh Wills <josh.wills@gmail.com> wrote:

> That's the sexiest thing I've seen in some time. +1 for a lambda module,
> but how does that work in Maven-fu? Is it like a conditional compile or
> something?
>
> On Fri, Dec 11, 2015 at 1:20 PM, David Whiting <davw@apache.org> wrote:
>
> > Oops, my bad. Here's a Gist:
> > https://gist.github.com/DavW/e2588e42c45ad8c06038
> >
> > On 11 December 2015 at 18:43, Josh Wills <josh.wills@gmail.com> wrote:
> >
> > > I think it's kind of awesome, but the attachment didn't go through- PR
> or
> > > gist?
> > > On Fri, Dec 11, 2015 at 7:42 AM David Whiting <davw@apache.org> wrote:
> > >
> > > > While fixing the bug where the IFn version of mapValues on
> > PGroupedTable
> > > > was missing, I got thinking that this is quite an inefficient way of
> > > > including support for lambdas and method references, and it still
> > didn't
> > > > actually support quite a few of the features that would make it easy
> to
> > > > code against.
> > > >
> > > > Negative parts of existing lambda implementation:
> > > > 1) Explosion of already-crowded PCollection, PTable and PGroupedTable
> > > > interfaces, and having to implement those methods in all
> > implementations.
> > > > 2) Not supporting flatMap to Optional or Stream types.
> > > > 3) Not exposing convenient types for reduce-type operations (Stream
> > > > instead of Iterable, for example).
> > > >
> > > > Something that would solve all three of these is to build lambda
> > support
> > > > as a separate artifact (so we can use all java8 types), and instead
> of
> > > the
> > > > API being directly on the PSomething interfaces, we just have
> > convenient
> > > > ways to wrap up lambdas into DoFns or MapFns via statically-imported
> > > > methods.
> > > >
> > > > The usage then becomes
> > > > import static org.apache.crunch.Lambda.*;
> > > > ...
> > > > someCollection.parallelDo(flatMap(d -> someFnOf(d)), pt)
> > > > ...
> > > > otherGroupedTable.mapValue(reduce(seq -> seq.mapToInt(i -> i).sum()),
> > > > ints())
> > > >
> > > > Where flatMap and reduce are static methods on Lambda, and Lambda
> goes
> > in
> > > > it's own artifact (to preserve compatibility with 6 and 7 for the
> rest
> > of
> > > > Crunch).
> > > > I've attached a basic proof-of-concept implementation which I've
> > tested a
> > > > few things with, and I'm very happy to sketch out a more substantial
> > > > implementation if people here think it's a good idea in general.
> > > >
> > > > Thoughts? Ideas? Suggestions? Please tell me if this is crazy.
> > > >
> > > >
> > >
> >
>

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