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Re: Remove "generic" multiply/divide operations from Quantity
- From: Otávio Gonçalves de Santana <
>
- To:
- Subject: Re: Remove "generic" multiply/divide operations from Quantity
- Date: Thu, 16 Oct 2014 20:44:26 -0300
@Martin.
I know generics has some limitations, but still powerfull to do a lot
of things:
About the question of Martin, Yes we can do and there are in in SE api such
java.util.Collections
<
http://docs.oracle.com/javase/7/docs/api/java/util/Collections.html>,
java.util.Arrays
<
http://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html>, etc.
List<Integer> intergers = Collections.emptyList();
List<String> strings = Collections.emptyList();
java.util.Set<Integer> intergersSet = Collections.emptySet();
java.util.Set<String> stringsSet = Collections.emptySet();
java.util.Map<String, Integer> map = Collections.emptyMap();
java.util.Map<String, String> map2 = Collections.emptyMap();
List<Long> longs = java.util.Arrays.asList(1L, 2L, 3L);
List<Integer> ints = java.util.Arrays.asList(1, 2, 4);
I can do something like this and still the Java language :)
On Thu, Oct 16, 2014 at 6:49 PM, Jean-Marie Dautelle
<
>
wrote:
>
Hi Guys,
>
I tred to read through the emails but I failed to understand the question
>
!!
>
Werner or Martin could you pose the question in simple terms that we can
>
all answer by yes or no.
>
I am in training all week but I will try to give you my opinion / response.
>
Cheers,
>
JM
>
>
On Thu, Oct 16, 2014 at 10:11 PM, Werner Keil
>
<
>
>
wrote:
>
>
> I left that conclusion ("pruning" of some methods or at least leaving
>
> them to implementations like UOMo or JScience did previously) as a possible
>
> option.
>
> It could be a little inconsistent as to where to apply them. If you had a
>
> Quantity type at least you'd need to cast it to SEQuantity (assuming that
>
> type exists in an SE specific implementation) or do all of your operations
>
> with SEQuantity<Q> after all. There both
>
> multiply(Number) and
>
> multiply(SEQuantity) or multiply(Quantity) could still exist.
>
>
>
> I'll try to phrase a quick question to the interested parties at Eclipse
>
> IoT. So far they said they prefer to stay without explicit classes, their
>
> response also was against a
>
> R multiply(Quantity<T>) because there are so many possible return types.
>
>
>
> About Martin's question, I can only give one example, but there are at
>
> least 50-70 cases in UCUM alone where asType() broke in JDK 8u20 and above.
>
> POUND_FORCE was
>
> Unit<Force> POUND_FORCE =
>
> addUnit(POUND.multiply(ACCELLERATION_OF_FREEFALL).asType(Force.class));
>
> but had to become
>
> Unit<Force> POUND_FORCE = addUnit(new ProductUnit<Force>(
>
> POUND.multiply(ACCELLERATION_OF_FREEFALL)));
>
>
>
> otherwise the SE port did not compile there any more
>
>
>
> Thanks,
>
> Werner
>
>
>
> On Thu, Oct 16, 2014 at 9:46 PM, Leonardo Lima
>
> <
>
>
> wrote:
>
>
>
>> Hello all.
>
>>
>
>> As Werner mentioned, I "abstained" from the voting because I understand
>
>> (as Otavio also pointed) that this is a more wide problem than our use
>
>> cases. API design is not my forte, I'll admit, but I'm keeping up with the
>
>> discussion.
>
>>
>
>> Still, I think it's valid that Martin (or Otavio or even I) write to
>
>> OpenJDK and ask about this, specially considering that we would like to be
>
>> part of the standard platform. I don't think this would bring bad
>
>> impression, au contraire, it should show that we care about what we're
>
>> doing specially outside our clique.
>
>>
>
>> In the end, I understood that:
>
>>
>
>> 1. What I (really) wanted can't be achieved without "exploding" the
>
>> JSR to have bajilion methods. That's not feasible.
>
>> 2. The convenient way to achieve somewhat what I wanted (the
>
>> signature that sparked this thread) breaks Java rules of generics
>
>> expectations. That's Martin's main point.
>
>> 3. The best way to continue with Generics is using the <?> and then
>
>> force the API user to cast.
>
>> 1. But, then, why not drop it from the signature?
>
>> 2. And add signature in JSR 363.1 when better support is
>
>> available in the language?
>
>>
>
>> Regards,
>
>> Leonardo.
>
>>
>
>> On Thu, Oct 16, 2014 at 4:42 PM, Otávio Gonçalves de Santana <
>
>>
>
>
>> wrote:
>
>>
>
>>> Martin, did you send the email?
>
>>> Please go a head.
>
>>> Le 17/10/14 02:54, Werner Keil a écrit :
>
>>>
>
>>> Do what you cannot leave, but note, unless either of the Spec Leads
>
>>> (Leonardo abstained from the ballot till he gets a better idea of the
>
>>> subject/discussion, Jean-Marie has been silent on all of it, maybe he is
>
>>> busy or has no opinion?) sanction that, it makes a bad impression of the
>
>>> work of the EG[?]
>
>>>
>
>>> I know it will make a bad impression. But frankly, if this group can
>
>>> not perform a logical analysis, we deserve it.
>
>>>
>
>>>
>
>>> We try to be as democratic as possible
>
>>>
>
>>> But main parts of my argument is about *logic*! Democracy has nothing
>
>>> to do in logic. Do you think that expressions like "*if A=B and B=C
>
>>> then A=C*" is a matter of opinion? On which of the following points do
>
>>> you disagree? (I explained those points in more details in my first
>
>>> today's
>
>>> email):
>
>>>
>
>>>
>
>>> 1. *LOGICAL FACT:* the "non-wildcards" proposal, when applied to
>
>>> the specific case of the Java language, can not be logically
>
>>> consistent.
>
>>> 2. *LOGICAL FACT:* going ahead despite the logical problem break
>
>>> the integrity of Java parametric type safety.
>
>>> 3. *OPINION:* The JSR-363 group has no authority for breaking the
>
>>> Java language that way.
>
>>>
>
>>>
>
>>> If I'm wrong on point 1 or 2, it should take you only 5 minutes to
>
>>> convince me: just point to the logical flaw in the arguments of my first
>
>>> today's email.
>
>>>
>
>>>
>
>>> Otavio changed the Dynamic Proxy version using Reflection in the SE
>
>>> port. And given there is no Reflection in ME 8, most of it also got
>
>>> applied
>
>>> to RI.
>
>>>
>
>>> Do we agree that SE can use reflection, and that ME take only a subset
>
>>> of quantity types?
>
>>>
>
>>>
>
>>> The only place you may refer to is the old JSR 275 code as there was
>
>>> no other QuantityFactory in the later API:
>
>>>
>
>>> https://kenai.com/projects/jsr-275/sources/svn-repository/content/trunk/jsr-275/src/main/java/javax/measure/quantity/QuantityFactory.java?rev=259
>
>>>
>
>>> Yes I was thinking about that class. It could be simplified a little
>
>>> bit.
>
>>>
>
>>>
>
>>> It returned the interface, but that at the time was "crippled", the
>
>>> Quantity had no operations.
>
>>>
>
>>> We can add the operations, no problem with that.
>
>>>
>
>>>
>
>>> And see JScience 4.x (intended as RI of JSR 275) that took Quantity
>
>>> and returned Quantity<?> or Quantity<Q> for all relevant operations, not
>
>>> Q
>
>>> [?]
>
>>>
>
>>> But nobody proposed to return Q! I explicitly wrote *Quantity<?>
>
>>> multiply(Quantity<?>)* in my previous email! I also wrote "*the old
>
>>> method signature was in my opinion the best we can achieve*". Energy
>
>>> is a subtype of Quantity<Energy>, which is itself assignable to
>
>>> Quantity<?>. Consequently a Quantity<?> multiply(Quantity<?>) method
>
>>> can return an instance of Energy. No need for thousands of methods or
>
>>> methods returning Q.
>
>>>
>
>>>
>
>>> We cannot do a "diff" between all unit systems, especially US or
>
>>> UCUM here, but if you do that diff, you'll see all the places that
>
>>> asType()
>
>>> simply broke the code starting with SE 8u20. Also look at SE port issues,
>
>>> especially all
>
>>> https://github.com/unitsofmeasurement/unit-impl-se/issues?q=is%3Aissue+is%3Aclosed
>
>>>
>
>>> I found no mention of 'asType' under that link and by browsing in the
>
>>> comments, but maybe I didn't looked hard enough. Anyway this is not the
>
>>> main issue, since we are not proposing a Quantity.asType(Class) method.
>
>>>
>
>>>
>
>>> Including the problems with asType().
>
>>>>
>
>>>> I'm sure that this problem does not exist.
>
>>>>
>
>>>
>
>>> It does, see above, in the SE 8 implementation there are very few
>
>>> cases where asType() did not break the code and it seems the remedy could
>
>>> be used to replace all existing calls.
>
>>>
>
>>> Then, please point me to a place where it broke the code. Is it
>
>>> possible to give me something more accurate than digging in the history
>
>>> of
>
>>> the entire project?
>
>>>
>
>>> Martin
>
>>>
>
>>>
>
>>
>
>
>
>
>
--
>
It is not the strongest of the species that survives, nor the most
>
intelligent. It is the one that is most adaptable to change. - Darwin's
>
Origin of Species (digest)
>
--
Otávio Gonçalves de Santana
blog:
http://otaviosantana.blogspot.com.br/
twitter:
http://twitter.com/otaviojava
site: *
http://about.me/otaviojava <
http://about.me/otaviojava>*
55 (11) 98255-3513
