I'm now implementing the toHash() function of my new Set class. But I'm not sure how to extract hash-information from an associative array of which the key-type can be anything. The values are irrelevant. So you might see the problem as extracting hash-information from its .keys array.

I'm sure the hash-information of its key-type can be retrieved, since that's how the associative array works in the first place. How do I retrieve it manually?

Thanks!

-- 
Michiel

Michiel wrote:

> I'm now implementing the toHash() function of my new Set class. But I'm not sure how to extract hash-information from an associative array of which the key-type can be anything. The values are irrelevant. So you might see the problem as extracting hash-information from its .keys array.
> 
> I'm sure the hash-information of its key-type can be retrieved, since that's how the associative array works in the first place. How do I retrieve it manually?

I think I found a way in Phobos, but it might not be the most elegant one. I used std.boxer to pack each element of the array into a box. Then I call the Box.toHash() function on each and use the sum to calculate the sets hash.

Is there a better way?

It does seem to work. I can now have sets of sets of sets of whatever, and it still works as expected.

I'll continue to tweak the class a bit and then I'll publish it here.

-- 
Michiel

"Michiel" <nomail@please.com> wrote in message news:eritp3$d3j$1@digitalmars.com...
> Michiel wrote:
>
> I think I found a way in Phobos, but it might not be the most elegant one. I used std.boxer to pack each element of the array into a box. Then I call the Box.toHash() function on each and use the sum to calculate the sets hash.
>
> Is there a better way?

You can use the .getHash method of the typeinfo any type, and it'll use the built in hashing function.

class Set(T)
{
    ...
    T[] values; // or however you store them

    void someFunc(T data)
    {
        hash_t hash = typeid(T).getHash(&data);
    }
}

Jarrett Billingsley wrote:

>> I think I found a way in Phobos, but it might not be the most elegant one. I used std.boxer to pack each element of the array into a box. Then I call the Box.toHash() function on each and use the sum to calculate the sets hash.
>>
>> Is there a better way?
> 
> You can use the .getHash method of the typeinfo any type, and it'll use the built in hashing function.
> 
> class Set(T)
> {
>     ...
>     T[] values; // or however you store them
> 
>     void someFunc(T data)
>     {
>         hash_t hash = typeid(T).getHash(&data);
>     }
> }

That also works nicely! I tried something similar, just not exactly like that. Anyway, it's more elegant than my box way.

Thanks!

-- 
Michiel