RFR: CR#8004561 : Additional Functional Interfaces and Updates

[Remi Forax]

On 12/24/2012 06:17 PM, Peter Levart wrote:
> On 12/24/2012 04:55 PM, Remi Forax wrote:
>> On 12/23/2012 07:36 PM, Brian Goetz wrote:
>>> Yes, this is a deliberate u-turn that comes as a result of the
>>> unexpected interactions with the overloading resolution rules.
>>
>> maybe it's because the overloading resolution rules are not the right 
>> ones ?
>> I've no idea if it's better or not, I'm just thinking loudly.
>>
>>> By having DoubleBlock extending Block<Double>, we created problems for
>>> overloading.  For example, consider this expected-to-be-common
>>> overloading in Bunch<T>:
>>>
>>>     <U> Bunch<U> transform(Function<T,U> transformer)
>>>         IntBunch transform(IntFunction<T> transformer)
>>>
>>> There are some conflicting rules in overload selection:
>>>    - prefer more-specific SAMs to less specific (favors IntFunction)
>>>    - prefer less boxing/unboxing
>>>
>>> What we'd like is to choose the former when the "natural" type of
>>> transformer is T -> Integer and the latter when the "natural" type is T
>>> -> int.  But, because the more specific rule has higher priority, we
>>> would coerce a T -> Integer into a T -> int (with unboxing) all the 
>>> time.
>>
>> Brian, Why the algorithm that select the most specific SAMs use the 
>> return type of the SAM descriptor,
>> the classical algorithm doesn't use the return type.
> I think Brian was referring to the most specific SAM type. The 
> "classical" algorithm prefers methods with more specific parameter 
> types and SAM type acts as parameter type here. If IntFunction<T> is a 
> subtype of Function<T, Integer> then the method with parameter of type 
> IntFunction<T> is selected in preference to Function<T, Integer> 
> regardless of lambda's "structural" or "natural" type, provided that 
> lambda conversion is valid for both.
>
> If parameter types of two overloaded methods are unrelated (not in a 
> sub-super-type relationship) then the "classical" algorithm barfs, but 
> lambda conversion can use structural properties of unrelated SAM types 
> to select the most appropriate in this case.

yes, I know, my question is why the algorithm uses the return type when 
comparing SAM types structurally ?

>
> Regards, Peter
>>
>> Rémi

regards,
Rémi

>>
>>>
>>>
>>>
>>>
>>> On 12/20/2012 9:07 PM, Howard Lovatt wrote:
>>>> 1. DoubleBlock doesn't extend Block<Double> and doesn't have a default
>>>> method, similarly int and long
>>>> 2. Similarly all the rest like Function aren't extended
>>>>
>>>> Is this the correct link - it seems to have gone backwards?
>>>>
>>>>    -- Howard.
>>>>
>>>>
>>>> On 21 December 2012 12:41, Mike Duigou <mike.duigou at oracle.com> wrote:
>>>>
>>>>> Hello all;
>>>>>
>>>>> Here are some additional functional interfaces for review. The 
>>>>> additions
>>>>> fill in holes for primitive types and for two operand "Bi" 
>>>>> operations.
>>>>>
>>>>> http://cr.openjdk.java.net/~mduigou/8004561/0/webrev/
>>>>>
>>>>> http://cr.openjdk.java.net/~mduigou/8004561/0/specdiff/java/util/function/package-summary.html 
>>>>>
>>>>>
>>>>> Additionally, this patch contains naming updates on the existing
>>>>> functional interfaces following 335 EG review. It does not include 
>>>>> the
>>>>> interface specializations and default methods previously proposed in
>>>>> CR#8004015. That proposal has been withdrawn. It turned out that user
>>>>> errors involving unexpected boxing were just too common for the value
>>>>> provided.
>>>>>
>>>>> Mike
>>>>>
>>>>>
>>>>
>>
>