Equivalent of Maps.uniqueIndex?

[Michael Nascimento]

I will give the next promotion a try, thanks Brian.

Regards,
Michael

On Fri, Jan 4, 2013 at 2:08 PM, Brian Goetz <brian.goetz at oracle.com> wrote:
> Suggestion: build from source or wait for the next promotion.  What is in
> b69 is probably just wrong.
>
>
> On 1/4/2013 10:59 AM, Michael Nascimento wrote:
>>
>> Ok, here we go.
>>
>> I can only use build 69. In this build, Tabulator.mappedTo type
>> parameters seem to be the other way around.
>>
>> Assume I have a bunch of entities with a getId() : Long. What I want is:
>>
>> // with Guava and JDK 8
>> Map<Long, Entity> entityById = Maps.uniqueIndex(entities, e -> e.getId());
>>
>> With pure JDK 8, here is my best attempt:
>>
>> Map<Long, Entity> entityById =
>> entities.parallelStream().tabulate(Tabulators.<Long,Entity>mappedTo(e
>> -> e.getId(), (i1, i2) -> i1));
>>
>> which doesn't work. This:
>>
>> entities.parallelStream().tabulate(Tabulators.<Entity,Long>mappedTo(e
>> -> e.getId(), (i1, i2) -> i1));
>>
>> compiles, but is pretty useless.
>>
>> Suggestions?
>>
>> Regards,
>> Michael
>>
>>
>> On Fri, Jan 4, 2013 at 1:41 PM, Brian Goetz <brian.goetz at oracle.com>
>> wrote:
>>>
>>> Stuff is in flux, apologies.
>>>
>>> In the current tip, Tabulators became Accumulators, and we have these
>>> versions which take a T->U, plus optionally a Supplier<Map> and a merge
>>> function (the default throws on duplicates.)
>>>
>>>      public static <T, U> Accumulator<T, Map<T,U>> mappedTo(Function<?
>>> super
>>> T, ? extends U> mapper) {
>>>          return mappedTo(mapper, (BinaryOperator<U>) THROWING_MERGER);
>>>      }
>>>
>>>      public static <T, U> Accumulator<T, Map<T,U>> mappedTo(Function<?
>>> super
>>> T, ? extends U> mapper,
>>>
>>> BinaryOperator<U> mergeFunction) {
>>>          return mappedTo(mapper, mergeFunction, (Supplier<Map<T,U>>)
>>> HashMap::new);
>>>      }
>>>
>>>      public static <T, U, M extends Map<T, U>> Accumulator<T, M>
>>> mappedTo(Function<? super T, ? extends U> mapper,
>>>
>>>    Supplier<M> mapSupplier) {
>>>          return mappedTo(mapper, (BinaryOperator<U>) THROWING_MERGER,
>>> mapSupplier);
>>>      }
>>>      public static <T, U, M extends Map<T, U>> Accumulator<T, M>
>>> mappedTo(Function<? super T, ? extends U> mapper,
>>>
>>>    BinaryOperator<U> mergeFunction,
>>>
>>>    Supplier<M> mapSupplier) {
>>>          return new MergingMapAccumulator<T, T, U, M>(mapSupplier,
>>> mergeFunction) {
>>>              @Override
>>>              public void accumulate(M map, T value) {
>>>                  accumulate(map, value, mapper.apply(value));
>>>              }
>>>          };
>>>
>>>      }
>>>
>>>
>>> On 1/4/2013 10:37 AM, Michael Nascimento wrote:
>>>>
>>>>
>>>> There is no mapTo() in Tabulators in build 69. There is a mappedTo,
>>>> but it takes a BinaryOperator. Which one am I supposed to use?
>>>>
>>>> Regards,
>>>> Michael
>>>>
>>>> On Fri, Jan 4, 2013 at 1:28 PM, Brian Goetz <brian.goetz at oracle.com>
>>>> wrote:
>>>>>
>>>>>
>>>>> tabulate(Tabulators.mapTo())
>>>>>
>>>>>
>>>>> On 1/4/2013 10:22 AM, Michael Nascimento wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> Guys,
>>>>>>
>>>>>> What is the equivalent in Lambda to Guava's Maps.uniqueIndex:
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> http://docs.guava-libraries.googlecode.com/git-history/release/javadoc/com/google/common/collect/Maps.html#uniqueIndex(java.lang.Iterable,
>>>>>> com.google.common.base.Function)
>>>>>>
>>>>>> I was trying the tabulate method, but couldn't find a method in
>>>>>> Tabulators with a single function that assumes the stream has unique
>>>>>> keys.
>>>>>>
>>>>>> Regards,
>>>>>> Michael
>>>>>>
>>>>>
>>>
>