Re: [boost] [multi-index] key_value

From: JOAQUIN LOPEZ MU?Z (joaquin_at_[hidden])
Date: 2006-08-20 19:28:16

Hello Tal,

----- Mensaje original -----
De: Tal Agmon <tal.boost_at_[hidden]>
Fecha: Domingo, Agosto 20, 2006 6:20 pm
Asunto: [boost] [multi-index] key_value

> Hi,
> 
> I am happy to work with multi_index library up till
> now I am able to operate successfully a 5 indices
> with my cranky msvc 6.5 comiler at work.

Remarkable, given the unstability of that old compiler.

> I do have a naive question
> 
> Is it possible to retreive all key values from an N
> index_type container? and how can I do it?

I don't understand the question. What do you mean by
"key value" and by "an N index_type container"? In case
the following is somewhat related to your problem,
here's how one can produce the key part of each element
of a given key-based index (uncompiled, expect typos.)

// multi_index_t is some multi-index container.
multi_index_t m;
...

// index N-th is key-based (for instance, ordered.)
typedef nth_index<multi_index_t,N>::type index_t;
const index_t& i=get<N>(m);
for(index_t::const_iterator it=i.begin();it!=i.end();++it){
  std::cout<<i.key_extractor()(*it)<<std::endl;
}

This code uses the member function key_extractor(), which
returns a copy of the internal key extractor, to extract
the key part of a given element.

In case your question is not addressed by the snippet
above, I'd appreciate if you could explain it a little more
clearly, possibly stating what your final goal is.

Thank you for using Boost.MultiIndex,

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo