Associative arrays in D and default comparators

[Walter Bright]

Sean Kelly wrote:
> Walter Bright wrote:
>> How do you do a hash for it if there's no constant data?
> 
> Using address, currently :-p  But that obviously has to change.  What 
> might make the most sense from a hash perspective would be something 
> like this:
> 
> class C {
>     hash_t hash;
>     hash_t toHash() {
>         if (hash != hash.init)
>             return hash;
>         hash = cast(hash_t) this;
>         return hash;
>     }
> }

That will fail if the object gets moved.

> But that leaves opCmp to wrestle with.  An "object id" would be a 
> reasonable universal solution, but I don't want to pay for the 
> synchronized op on construction.  I suppose I'm simply having a hard 
> time getting over the idea that an object's address is is not a unique 
> identifier in GCed languages.

An opCmp has the same problem that toHash does; fix it for either and it 
is fixed for both. I think you'll have to do a unique id for each in 
order to store them in an AA, or else wait until the thread id is 
assigned before storing it.