Tricky semantics of ranges & potentially numerous Phobos bugs

[Timon Gehr]

On 10/17/2012 07:20 PM, Andrei Alexandrescu wrote:
> On 10/16/12 3:41 PM, H. S. Teoh wrote:
>> I think with D's compile-time introspection capabilities, it _should_ be
>> possible to implement a generic deepCopy template that works for any
>> type.
>>
>> Of course, then one has to address tricky issues such as complex data
>> structures that have interlinking parts; a blind recursive deep-copy may
>> not have the desired effect (e.g., if we're deep-copying a graph and
>> there are multiple paths (via references) to the same node, then we
>> shouldn't end up with multiple copies of that node). Some care will also
>> need to be taken to deal with cyclic structures, etc.. And some
>> optimizations can probably be done to avoid copying immutable objects,
>> since that would be a waste of time&  memory.
>>
>> Probably some kind of graph traversal algorithm can be used to address
>> these issues, I think, perhaps with the help of an AA or two to recreate
>> the original linking structure in the copy.
>
> Yes, deepDup should be implementable as a library and use a temporary
> dictionary of already-duplicated items to avoid infinite recursion.
>
> We should add that to Phobos - could you please add a task to trello.
>
>
> Andrei
>

A deepDup is missing information about what is representation and what
is just a reference kept in order to access external data, so it is
quite useless.