Samuel Charron writes:

On Fri, Dec 4, 2009 at 9:58 PM, Joaquin M Lopez Munoz wrote:

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Samuel Charron writes:

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I'd want to have a multi_index storing containers, and have one index based on all the contained elements. For example: two vectors [1 2 3] and [3 4] would be indexed as 1 -> [1 2 3] 2 -> [1 2 3] 3 -> [1 2 3] [3 4] 4 -> [3 4]

How would you do that ?

If I'm understanding your question well, you can do like this: [...]

With your solution, my containers are sorted using all their values, it's not what I meant.

My problem is that from any element from the container, I want to be able to retrieve the whole container.

My index type would be the element contained, and the type of element contained in the multi_index would be the container type. The indices inserted would be all elements from my container, and the element would be one occurence of the container.

Ok, now I got it. The short ansewer is that Boost.MultiIndex does not provide any off-the-shelf way to do what you want, basically because each element (each vector in your case) appears exactly once in any given index. Long answer: you can approach your scenario by storing "container positions" rather than containers and manually inserting for each new conainer as many different positions as elements has the container. Kind of as sketched in the following program: #include #include #include #include #include #include <vector> template<typename Container> struct container_pos { typedef typename Container::value_type value_type; typedef boost::shared_ptr<Container> container_ptr; container_pos(container_ptr ptr,std::size_t pos):ptr(ptr),pos(pos){} const value_type& get()const{return (*ptr)[pos];} container_ptr ptr; std::size_t pos; }; typedef std::vector<int> container_type; typedef boost::shared_ptr container_ptr; typedef container_pos element; using namespace boost::multi_index; typedef multi_index_container< element, indexed_by< ordered_non_unique< const_mem_fun > >

multi_t;

template void multi_insert(PosContainer& c,boost::shared_ptr<Container> ptr) { for(std::size_t i=0,n=ptr->size();i

Samuel Charron escribió:

On Tue, Dec 8, 2009 at 9:01 PM, Joaquin M Lopez Munoz wrote:

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Ok, now I got it. The short ansewer is that Boost.MultiIndex does not provide any off-the-shelf way to do what you want, basically because each element (each vector in your case) appears exactly once in any given index.

Long answer: you can approach your scenario by storing "container positions" rather than containers and manually inserting for each new conainer as many different positions as elements has the container. Kind of as sketched in the following program:

<code snippet>

Is this what you're after?

Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

Yes that's it. I tried something similar, using boost::flyweight (hence my question about scoped flyweights).

I tried to write another kind of index for BMI some time ago, and if I remember correctly, there is no way to map an element to multiple values of an index. Do you think of anything to point into the code of BMI to try doing it ?

I don't think BMI can be tweaked in that way. The idea that each element is mapped exactly once into each index is a fundamental one in the design of the library.

Do you have any kind of documentation about writing an index for BMI (to be sure what I'm writing is safe) ?

No, I'm afraid I don't. If you plan on writing a custom index of your own do not hesitate to come back for help. Others have done in the past, it's not particularly difficult if you take one of the current indices as your starting point. Anyway, I doubt there's a nice way to implement your multiple-value idea. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo