Re: [Boost-users] [bimap] How to erase a single association in a many-to-many bimap?

Subject: Re: [Boost-users] [bimap] How to erase a single association in a many-to-many bimap?
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2012-05-15 06:43:02

Le 15/05/12 12:09, Vicente J. Botet Escriba a écrit :
> Hi,
>
> I have a bimap
>
> typedef bimap<
>     multiset_of<  tagged< Person*,                     consultant> >,
>     multiset_of<  tagged< Company*,                 client> >,
>     with_info<    tagged< ConsultancyContract*, contract> >
> > Consultancy;
>
> initialized as follows
>
>   Consultancy consultancy;
>   Person John("John"), Jane("Jane");
>   Company Dell("Dell"), HP("HP");
>   ConsultancyContract JohnContractD(10,1);
>   ConsultancyContract JaneContractD(20, 2);
>   ConsultancyContract JaneContractH(30, 3);
>
>   consultancy.insert(Consultancy::value_type(&Jane, &Dell, 
> &JaneContractD));
>   consultancy.insert(Consultancy::value_type(&Jane, &HP, 
> &JaneContractH));
>
> and I want to remove only the specific association Jane<->Dell and so 
> I'm using
>
>   consultancy.erase(Consultancy::value_type(&Jane, &Dell));
>
> but then the resulting consultancy bimap is empty, while I expect the 
> association Jane<->HP to be there yet.
>
> If I add before erasing
>   consultancy.insert(Consultancy::value_type(&John, &Dell, 
> &JohnContractD));
>
> and then
>   consultancy.erase(Consultancy::value_type(&Jane, &Dell));
>
> all the associations concerning Jane are removed.
>
> What I'm doing wrong? How to erase a single association?
>
I have reached to get what I was locking for.

I have added  set_of_relation<> to the bimap definition

typedef bimap<
     multiset_of<  tagged< Person*,                     consultant> >,
     multiset_of<  tagged< Company*,                 client> >,
     with_info<    tagged< ConsultancyContract*, contract> > ,
     multiset_of_relation<>
 > Consultancy;

Is there another way when the collection of relation is the default 
|left_based?
|I find the default behavior a little bit surprising. Why provide a 
erase function requesting the value_type if only the left side is taken 
in account?
|
What is the rationale to have the default left_based? Space optimization?

It works also with multiset_of_relation. I don't see a use case for 
this. When the user could want the same association to be several times? 
Could some one give me an example?

Best,
Vicente
|