Re: [boost] [MultiIndex] Recursive data structure with MultiIndex

Subject: Re: [boost] [MultiIndex] Recursive data structure with MultiIndex
From: Sebastian Redl (sebastian.redl_at_[hidden])
Date: 2009-05-28 11:09:20

joaquin_at_[hidden] wrote:
> Sebastian Redl escribió:
>> Hi,
>>
>> I'm trying to implement property_tree in terms of multi_index, but have
>> run into a problem.
>>
>> The old implementation boiled down to this (using no templates for
>> clarity):
>>
>> class ptree
>> {
>>   typedef std::pair<std::string, ptree> value_type;
>>   typedef std::list<value_type> list_type;
>>   list_type m_children;
>> };
>>
>> This is undefined behavior, because at the point where the list is
>> instantiated, ptree is incomplete, so the pair cannot be fully
>> instantiated. However, apparently it worked on enough compilers.
>>
>> Now I want to use MultiIndex instead, so that I can have both the order
>> of children preserved and offer O(log(N)) lookup of children. (The old
>> code was O(N), but claimed to be O(log(N)).) But MultiIndex actually
>> fails to instantiate with the incomplete type.
>
> Please disregard the previous mail, I answered too quickly and wrongly.
> multi_index_container *can't* be instantiated with an incomplete type,
> regardless of the kind of key extractors you're using; as things
> stands now,
> instantiating a multi_index_container<T,...> implies the instantiation
> of its internal
> node type, which needs to know sizeof(T).
OK, good to know.

Does multi_index support any move_ptr emulation we have in boost? (Do we
have any move_ptr emulation in boost?) I can live with making the
element a pointer, but I'd much rather it not be a raw pointer, and I
have no use for reference counting overhead either.

Sebastian