Re: Traits and iterators

["Alejandro R. Mosteo" <alejandro@mosteo.com>]

On 08/06/16 09:31, briot.emmanuel@gmail.com wrote:
>> generic
>>      with package Elements is new Elements_Policy (<>);
>>      type Container is private;
>>      type Cursor is private;
>>      with function First (Self : Container) return Cursor is <>;
>>      with function Has_Element
>>         (Self : Container; C : Cursor) return Boolean is <>;
>>      with function Element (C : Cursor) return Elements.Element is <>;
>>      with procedure Next (C : in out Cursor) is <>;
>> package Forward_Cursors_Policy is
>> end Forward_Cursors_Policy;
>>
>> That, in itself, I don't think will give the ability to use "of" in
>> iterations, although it enables one to iterate over an unknown type.
>
>
> Indeed, this signature package allows you to write an explicit iteration loop, where
> you manipulate cursors explicitly. I don't know, and I don't think it is doable, how to
> pass a formal type and mention that it should be iterable in the sense of the "for..of"
> loop.
> That means that any generic algorithm we write will take the above Policy package,
> but will not be able to use "for..of". That's a bit more work to write, but just as
> efficient in the end, but perhaps a limitation in the language.

Thanks for the confirmation. Sometimes I miss interfaces for these 
things in the language.

Álex.