Locking data

[Malte]

On Wednesday, 23 May 2018 at 13:24:35 UTC, rikki cattermole wrote:
> On 24/05/2018 1:20 AM, Malte wrote:
>> On Tuesday, 22 May 2018 at 21:45:07 UTC, IntegratedDimensions 
>> wrote:
>>> an idea to lock data by removing the reference:
>>>
>>> class A
>>> {
>>>    Lockable!Data data;
>>> }
>>>
>>> [...]
>> 
>> This sounds like you are looking for is an atomic swap. Afaik 
>> it doesn't exist in the standard library. You could use asm 
>> for the XCHG, but that would make your code x86 dependent.
>> I think the easiest way would be to just use a mutex and 
>> tryLock.
>
> What are you talking about? :p
>
> http://dpldocs.info/experimental-docs/core.atomic.cas.1.html

That is Compare-and-set.
To make an exchange using cas I first have to read the value, 
then write to it expecting to be still the value I read before. 
That are more instructions than just a swap. If a cas fails, I 
have to redo everything. An exchange never fails, I just might 
not get the result I would like to have (null instead of pointer).