Empty value type ?

Kirk Pepperdine kirk.pepperdine at gmail.com
Tue Jun 26 21:37:00 UTC 2018


Feels like a value type version of null.

Kind regards,
Kirk

> On Jun 26, 2018, at 9:43 PM, Brian Goetz <brian.goetz at oracle.com> wrote:
> 
> Zero-length values can be quite useful, just not directly.  Look at the current implementations of Set that delegate to HashMap; all that wasted space.  When we have specialized generics, they can specialize to HashMap<T, empty>, and that space gets squeezed away to zero.  
> 
>> On Jun 26, 2018, at 11:36 AM, Kirk Pepperdine <kirk.pepperdine at gmail.com> wrote:
>> 
>> How can a value type be empty.. what is an empty integer? An empty string? Just curious.
>> 
>> Kind regards,
>> Kirk
>> 
>> 
>> 
>>> On Jun 26, 2018, at 3:28 PM, forax at univ-mlv.fr wrote:
>>> 
>>> ok,
>>> in that case, i think zero field value types should be rejected by the compiler.
>>> 
>>> Rémi
>>> 
>>> ----- Mail original -----
>>>> De: "Tobias Hartmann" <tobias.hartmann at oracle.com>
>>>> À: "Remi Forax" <forax at univ-mlv.fr>, "valhalla-dev" <valhalla-dev at openjdk.java.net>
>>>> Envoyé: Mardi 26 Juin 2018 15:23:46
>>>> Objet: Re: Empty value type ?
>>> 
>>>> Hi Remi,
>>>> 
>>>> no, empty value types are not planned to be supported for LW1.
>>>> 
>>>> Best regards,
>>>> Tobias
>>>> 
>>>> On 26.06.2018 15:19, Remi Forax wrote:
>>>>> Is empty value type targeted for LW1 ?
>>>>> 
>>>>> Error: LinkageError occurred while loading main class GenBug
>>>>> 	java.lang.ClassFormatError: class: GenBug - Value Types do not support zero
>>>>> 	instance size yet
>>>>> 
>>>>> Rémi
>> 
> 



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