Iterable::forEach not returning Iterable

[Tomasz Kowalczewski]

I understand that forEach is eager and do not suggest it should be
changed (although I can imagine lazy versions on some specialized
collections working just fine for the user). This is rather an
argument towards something that potentially is more user friendly and
is based on the fluent interface pattern. Iterable::into is eager and
does return a collection which allows user to chain the calls further,
why not forEach then?

Also, if some collection can be a start to a lazy->lazy->eager chain
of calls then I do not see why operation such as forEach cannot be a
start of another such chain (l->l->e->l etc..).

Tomasz

On Thu, May 17, 2012 at 7:16 PM, François Sarradin <fsarradin at gmail.com> wrote:
> There are monads for these... ;)
>
> francois-
> Le 17 mai 2012 16:30, "Rémi Forax" <forax at univ-mlv.fr> a écrit :
>
>> On 05/17/2012 04:05 PM, Brian Goetz wrote:
>> > Of course, no one would write production code like this.  Mappers are
>> > supposed to be side-effect-free.  But it is an acceptable sin for
>> > temporary debugging code.
>>
>> Haskell guys, please don't read ...
>>
>> but logging is side effect free until you read the log in the program.
>>
>> Rémi
>>
>> >
>> > On 5/17/2012 9:26 AM, Remi Forax wrote:
>> >> You can use
>> >>    map(it ->  {
>> >>       Log.log(it);
>> >>       return it;
>> >>     }).
>> >> instead of forEach.
>> >>
>> >> Rémi
>> >>
>> >> Sent from my Phone
>> >>
>> >> ----- Reply message -----
>> >> From: "Tomasz Kowalczewski"<tomasz.kowalczewski at gmail.com>
>> >> To: "lambda-dev"<lambda-dev at openjdk.java.net>
>> >> Subject: Iterable::forEach not returning Iterable
>> >> Date: Thu, May 17, 2012 12:33
>> >>
>> >>
>> >> Hi,
>> >>
>> >> I was trying out the new jdk8 build with lambdas and while doing some
>> >> simple towards-lamda-refactoring I stumbled on following use case:
>> >>
>> >> List<File>  files...
>> >> files.filter( File::isFile ).filter( ... ).map(
>> >> ConfigurationFile::new );
>> >>
>> >> I wanted to inject some debugging code inside this chain using forEach
>> >> and realized that it returns void and not Iterable. Its default
>> >> delegates to Iterables::forEach that returns Interable, so I guess it
>> >> is just a matter of deciding if forEach should seal the pipe or allow
>> >> more processing.
>> >>
>> >> Based on my example I think there is a great value in changing the
>> >> return type from void as in my opinion it will be harder to debug and
>> >> step through such lambdanized code than through several (ugly)
>> >> for-each loops doing same work.
>> >>
>> >> P.S.: Atttaching eclipse debugger to this code being run in a simple
>> >> main() instantly crashes the debugged JVM. But I guess debugging is
>> >> not yet supported anyway :)
>> >>
>>
>>
>>
>