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Re: stream collect with own class

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On 12/5/2015 10:36 AM, Philipp Kraus wrote:
> Am Samstag, 5. Dezember 2015 14:34:21 UTC+1 schrieb Eric Sosman:
>> On 12/4/2015 5:46 PM, Philipp Kraus wrote:
>>> Am Freitag, 4. Dezember 2015 14:58:48 UTC+1 schrieb Eric Sosman:
>>>> On 12/4/2015 8:12 AM, Philipp Kraus wrote:
>>>>> Hello,
>>>>>
>>>>> I'm using streams and I would like to create "fuzzy logic implications". In short call, I have a collection with
>>>>>
>>>>> Set<IFuzzy> x;
>>>>>
>>>>> and my IFuzzy interface is defined like
>>>>>
>>>>> public interface IFuzzy
>>>>> {
>>>>>         public Boolean getResult();
>>>>>
>>>>>         public Double getFuzzy();
>>>>> }
>>>>>
>>>>> I run in my code
>>>>>
>>>>> IFuzzy y = x.stream()......
>>>>>
>>>>> I would like to implode / aggregate each IFuzzy object into one result, so I need to call on each element from x the getResult() and the getFuzzy() method and collect / implode the data.
>>>>>
>>>>> How can I do this call with a stream operation? IMHO I need to write an operator like allMatch()
>>>>
>>>>        If I understand you correctly, you want to combine information
>>>> from many IFuzzy's into a single IFuzzy instance.  (Just ignore me
>>>> if I've understood *in*correctly.)  In that case, you need some kind
>>>> of a .reduce() operation, either something from the Collectors class
>>>> or something you write yourself.
>>>
>>> Yes, that's correct. I have found the Collector<T,A,B> interface, but how I can implement this in a correct way (for stream and parallelstream)? IMHO T is the type IFuzyy, but A and B? Is is correct to define T=A=B => Collector<T,T,T> ?
>>
>>       Why would you want a Collector?  You're trying to combine a Set of
>> IFuzzy's into *one* IFuzzy, not into a collection of (modified, derived,
>> whatever) IFuzzy's.
>>
>>       (Aside: The JavaDoc for SE 8 lists gives Collector's type parameters
>> as <T,A,R>, not <T,A,B>.  Did you misread R as B, or are you looking at
>> some other description?)
>>
>>       I'm still not clear on what you're trying to do.  Perhaps it would
>> help me understand if you showed the IFuzzy's => IFuzzy transformation:
>> How would you write it using a plain old `for(IFuzzy i : x)' loop?
>
> Okay, yes I miss this information. The transformation can be a logical or (||) of the boolean values
> and a min of each floating point value. But there are a lot of more tranformation algorithms, see
> https://en.wikipedia.org/wiki/T-norm#Prominent_examples
> Reduction like Hamacher product is a little bit difficult, because I need an algebraic expression to calculate the floating point value, so imho I need access to all elements within the stream

     If you can't show me the transformation you want to perform,
I can't help you package it as a stream operation.  Sorry, but the
Wikipedia page (which describes *binary* operations) does not convey
to me the nature of the N-ary transformations that interest you.

     All I can suggest is that you write a plain old for-loop.  For
one thing, it may suffice for whatever your needs are.  For another,
if you'll show us your for-loop maybe somebody can show you how to
reformulate it as a stream operation.  For yet another, NetBeans (and
perhaps other IDE's) can sometimes do the reformulation for you: You
write your for-loop and NetBeans offers to rearrange it -- the form it
chooses isn't always the slickest possible, but even so it gives you a
good running start.

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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stream collect with own class Philipp Kraus <philipp.kraus.flashpixx@gmail.com> - 2015-12-04 05:12 -0800
  Re: stream collect with own class Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-12-04 08:58 -0500
    Re: stream collect with own class Philipp Kraus <philipp.kraus.flashpixx@gmail.com> - 2015-12-04 14:46 -0800
      Re: stream collect with own class Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-12-05 08:34 -0500
        Re: stream collect with own class Philipp Kraus <philipp.kraus.flashpixx@gmail.com> - 2015-12-05 07:36 -0800
          Re: stream collect with own class Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-12-05 10:57 -0500

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