Re: [Boost-users] [multi_index] non-intrusive keys

From: Adi Shavit (adish_at_[hidden])
Date: 2005-10-31 01:19:55

Hi Joaquin,

 Thanks for the quick answer.

>I don't think you can avoid duplication of keys --if the
>keys are really expensive to duplicate, you might consider
>holding shared_ptrs to them, but this is AFAICS the furthest
>you can get.
>  
>
I see.
My question is actually more general, than copy-ctor issues.
Often you might like to insert existing objects into a container, ones 
that do not have the indexing keys in them.
But I guess, this is what makes multi_index more like std::set than 
std::map.

>Take into acount that a multi_index_container with two keys
>is not a map of maps. These are different beasts, serving different
>purposes,
>
>* a map of maps applies two concatenated lookups to get
>to a "terminal" object,
>* a multi-index container with two indices applies either one
>of two poosible lookups to get to the object,
>
>so you might want to ask yourself whether it makes sense
>to try to replace your current code with Boost.MultiIndex.
>What are the advantages / use cases you envision?
>
>  
>
Well, I guess you're right.
Initially I thought I could use it to "cut" the elements according to 
the various indices, like a lightweight DB.

BTW, is there some C++ other data structure library (in boost or out), 
that might fit the bill?
I really don't need a full fledged DB, just "map-of-maps..." with 
readable semantics.

Thanks,
Adi