Re: [boost] [multi-index] key_value

From: Tal Agmon (tal.boost_at_[hidden])
Date: 2006-08-21 09:49:49

Joaquin,

It works !

>From some reason the point I made In the latter code shows this strange results
But then when I tried this sample on another non_unique_index the
results was correct. then I had to figure out what the ...

the cure was to rebuild the project (...or maybe a coffee break for me
and my computer).

Other than that I appreciate your efforts and you can ignore my previous post
I should be getting a new compiler which will be more friendly pretty soon.

Regards,

On 8/21/06, Tal Agmon <tal.boost_at_[hidden]> wrote:
> >Still I'm having difficulties with understanding your question, but let me
> > try my hand
>
> Your are good! :) I should knock myself for not sending you a snippet code
>
> below you can fiind a "small" example with only 2 indices
>
> ******** BEGIN CODE ********
>
> typedef int handle;
> typedef int group_id;
>
>
> struct NodeBase:boost::enable_shared_from_this<NodeBase>
> {
>
>  virtual ~NodeBase(){}
>
>  virtual group_id memberOf()const=0;
>  virtual handle   getHandle()const=0;
> };
>
> struct NodeType:NodeBase
> {
>  NodeType(handle h,group_id gid):h(h),gid(gid){}
>
>
>  virtual group_id memberOf()const{return gid;}
>  virtual handle   getHandle()const{return h;}
>
>
> private:
>  group_id gid;
>  handle   h;
> };
>
>
> struct NodeBaseHandleExtractor
> {
>  typedef handle result_type;
>  result_type operator()(const boost::shared_ptr<NodeBase>& x)
>  {
>   return x->getHandle();
>  }
> };
>
> struct NodeBaseGroupIdExtractor
> {
>  typedef group_id result_type;
>  result_type operator()(const boost::shared_ptr<NodeBase>& x)
>  {
>   return x->memberOf();
>
>  }
> };
>
> typedef boost::multi_index::multi_index_container<
>  boost::shared_ptr<NodeBase>,
>  boost::multi_index::indexed_by<
>   boost::multi_index::ordered_unique<
>
>     NodeBaseHandleExtractor
>
>   >,
>   boost::multi_index::ordered_non_unique<
>
>     NodeBaseGroupIdExtractor
>
>   >
>  >
> > NodePtrSet;
>
> int main()
> {
>  NodePtrSet ns;
>
>  typedef boost::shared_ptr<NodeBase> element_type;
>
>  ns.insert(element_type(new NodeType(0,10))); // 0 = id, 10 = group_id
>  ns.insert(element_type(new NodeType(1,10)));
>  ns.insert(element_type(new NodeType(2,20)));
>
> // Now lets say I want to get a list of unique group_id values.
> // so I should get {10,20} event thought I have 3 elements
>
> //if i use the following
> for(index_t::const_iterator it=i.begin();it!=i.end();){ // note: no ++it
>  // output the key
>
>  std::cout<<i.key_extractor()(*it)<<std::endl;
>
>  // jump to the next different key value ( which is great btw)
>  it=i.upper_bound(i.key_extractor()(*it));
> }
>
> //Note that the for loop still iterates 3 times and not 2 times.
> // Meaning that the results of the key_extractor()(*it) key_value are
> {10,10,20}
>
> // My goal is to get back just {10,20} and not {10,10,20}
> //assuming that in this non_unique_index container the key (group_id)
> is at least unique even though 10 points to 2 elements.
>
>  return 0;
> }
>
> I hope I made my point this time.
>
> Regards
> Tal Agmon
>
> On 8/21/06, Joaquín Mª López Muñoz <joaquin_at_[hidden]> wrote:
> > Tal Agmon ha escrito:
> >
> > > Hi Joaquin,
> > >
> > > Sorry for the lack of info in my previous quote.
> > > I appreicate your affort to promptly help me.
> > >
> > > What I have is a non_unique which I carry to get all the keys.( I
> > > don't care about the elements)
> > >
> > > My guess is that key_extractor()  returns a key_form_element, is quite
> > > redundant in my case.
> > >
> >
> > Hello again.
> >
> > Still I'm having difficulties with understanding your question, but let me
> > try my hand: are you looking for a way to produce all *different* key
> > values contained by an index? If so, something like the following would do:
> >
> > for(index_t::const_iterator it=i.begin();it!=i.end();){ // note: no ++it
> >  // output the key
> >  std::cout<<i.key_extractor()(*it)<<std::endl;
> >
> >  // jump to the next different key value
> >  it=i.upper_bound(i.key_extractor()(*it));
> > }
> >
> > Now, is this what you were asking about?
> >
> > >
> > > Regards
> > > Tal
> > >
> >
> > Best,
> >
> > Joaquín M López Muñoz
> > Telefónica, Investigación y Desarrollo
> > _______________________________________________
> > Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
> >
>