Re: [boost] Associative container using a vector

Le 31/03/13 19:48, Stefan Strasser a écrit :

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struct A{ vector<Value> values; vectorstd::size_t freelist; map index;

void erase(...){ push index of unused value to freelist; } void push_back(Value){ reuse a freelist entry or values.push_back; } }; struct B{ vector data; }; Am 31.03.2013 19:22, schrieb Michael Marcin: template<class Value> class index;

template class vector_map;

Is there anything like that?

Is this multi-index?

I don't think so. At least I can't find it. You could implement my "struct A" above using Boost.MultiIndex as it uses a vector and a map, but I can't find a map implementation that uses a vector with empty values for almost-contiguous keys. keep in mind the one-to-many relationship between A and B. I'd like to be able to do ONE map lookup to receive a key with which you can access many associated data values in B objects.

Hi, The architecture of Boost.MultiIndex don't need shuch a double indirection. Is as if you had the A and the Bs in a single Node. IIRC, I believe the a and the bs instances must be created at once when inserting on the multiindex. Your approach is to map values of type A to a continuous index and then use this index to access other vectors of Bs. This could work on some cases, but ensuring that the index associated to a specific 'a' doesn't change is not easy to preserve if the lookup for the index must be fast. The main difference of both approaches is that Boost.Multiindex insert all (A and the Bs at once), while your design allows to insert A and the Bs independently. An alternative to consider could be to create a multiindex with A and pointers to Bs. Best, Vicente