Primitive streams and optional

[Remi Forax]

On 12/05/2012 01:56 PM, Doug Lea wrote:
> On 12/05/12 07:42, Remi Forax wrote:
>> This experience among others led to the non-nulls policy in j.u.c.
>>
>> If we can go back in time and disallow null for all collections, we 
>> will live in
>> a better world, but that not the case.
>
> If we could go back in time and disallow null for all streams, we will
> live in a better world. Oh, wait! We don't have to go back in time!
> We can just make a better world!

That was the first idea, but there is not a lot of streams that are not 
baked by a collection.
If we don't tolerate null in stream, we create an island with nice rules 
inside the island and a hell for people that want to go to that island 
or go out of that island. And we don't want a million of devs to become 
number 6, right ? [1].

>
>
>> I'm pretty sure that because j.u.c collections use null to tag entry 
>> that should
>> be removed and because the VM aggressively optimizes value that was 
>> never null
>> before, code that triggers de-optimization the first time you remove 
>> an element
>> from a concurrent collection should exist.
>
> I'm pretty sure that all such cases are OK because they trigger
> different branches that would somehow need encoding anyway.
> So branching on null vs branching on something else is a wash.
> (Although there might be a case here and there where different
> encodings might win because they currently disable triggerings
> of agressive-null mechanics that would otherwise be enabled
> along branches.
>
>
> -Doug
>
>

Rémi

[1] https://en.wikipedia.org/wiki/The_Prisoner