Hi everybody,

I would like to extract key and value type from AA.

I found this answer on forum :

template AATypes(T)
{
  // todo: static assert if T is no AA type here

  alias ArrayElementType!(typeof(T.keys)) key;
  alias ArrayElementType!(typeof(T.values)) value;
}

But compiler failed,I think T need to be a value in order to get keys and values attributes.

So how can I get types without instance ?
Thanks for help.

On Saturday, 19 September 2015 at 12:50:51 UTC, Pierre wrote:
> So how can I get types without instance ?
> Thanks for help.

---------->8---------

template AATypes(T)
{
  // todo: static assert if T is no AA type here

  alias ArrayElementType!(typeof(T.init.keys)) key;
  alias ArrayElementType!(typeof(T.init.values)) value;
}


---------->8---------


Should work.

On Saturday, 19 September 2015 at 12:52:19 UTC, ponce wrote:
> On Saturday, 19 September 2015 at 12:50:51 UTC, Pierre wrote:
>> So how can I get types without instance ?
>> Thanks for help.
>
> ---------->8---------
>
> template AATypes(T)
> {
>   // todo: static assert if T is no AA type here
>
>   alias ArrayElementType!(typeof(T.init.keys)) key;
>   alias ArrayElementType!(typeof(T.init.values)) value;
> }
>
>
> ---------->8---------
>
>
> Should work.

You're right it's OK now.
Thank you.

On Saturday, 19 September 2015 at 12:50:51 UTC, Pierre wrote:
> Hi everybody,
>
> I would like to extract key and value type from AA.
>

You can also do it with built-in syntax:

template AATypes(AA : K[V], K, V)
{
    alias Key = K;
    alias Value = V;
}

On Saturday, 19 September 2015 at 18:13:09 UTC, Marc Schütz wrote:
> On Saturday, 19 September 2015 at 12:50:51 UTC, Pierre wrote:
>> Hi everybody,
>>
>> I would like to extract key and value type from AA.
>>
>
> You can also do it with built-in syntax:
>
> template AATypes(AA : K[V], K, V)
> {
>     alias Key = K;
>     alias Value = V;
> }

I see, maybe .KeyType and .ValueType should be integrated in AA.
Or like C++ with map, make a ValueType(::value_type) field wich contain a pair of type.

On Saturday, 19 September 2015 at 18:13:09 UTC, Marc Schütz wrote:
> You can also do it with built-in syntax:
>
> template AATypes(AA : K[V], K, V)
> {
>     alias Key = K;
>     alias Value = V;
> }

K[V] supposed to be V[K] btw...

On 09/20/2015 12:47 AM, Pierre wrote:

> I see, maybe .KeyType and .ValueType should be integrated in AA.
> Or like C++ with map, make a ValueType(::value_type) field wich contain
> a pair of type.

Currently, they are templates in std.traits:

  http://dlang.org/phobos/std_traits.html#KeyType

Ali

On Sunday, 20 September 2015 at 09:34:15 UTC, Ali Çehreli wrote:
> On 09/20/2015 12:47 AM, Pierre wrote:
>
>> I see, maybe .KeyType and .ValueType should be integrated in AA.
>> Or like C++ with map, make a ValueType(::value_type) field wich contain
>> a pair of type.
>
> Currently, they are templates in std.traits:
>
>   http://dlang.org/phobos/std_traits.html#KeyType
>
> Ali

Nice! thank you for the information.