Re: [Boost-users] [bimap] Creating a bimap fom a std::map

Subject: Re: [Boost-users] [bimap] Creating a bimap fom a std::map
From: Matias Capeletto (matias.capeletto_at_[hidden])
Date: 2009-11-25 13:46:52

On Wed, Nov 25, 2009 at 1:24 PM, Edward Diener <eldiener_at_[hidden]> wrote:
> Matias Capeletto wrote:
> My opinion is that you should have a constructor which takes a std::map,
> where the types of the map are the types of the bimap. If the types of the
> map are the same as the types of the bimap, then the constructor should do
> exactly the equivalent to what you show just above. If the types of the map
> are the reverse of the types of the bimap, then the constructor should be
> the equivalent of:
>
> std::map<std::string,int> myMap;
> // ... fill myMap
> boost::bimap<int,std::string> myBimap;
> myBimap.right.insert(myMap.begin(),myMap.end());
>
> This is an ease of use issue and I really do not see why you can not make
> the use of bimap easier to use in this way. Especially since you also agree
> that this is a very common scenario.

I understand your easy-of-use point, but you have just wrote down here
why it is not a good idea to provide this constructor. Not only it
breaks the symmetry, the real problem is that following your idea of
automatic conversion between pairs and relations we bump into
ambiguities. Imagine you now have a bimap<A,A>, and you use your
constructor with a map<A,A>... it is not clear which side is the left
and which side is the right. I thought about this issues and it was
decided that it is better not to surprise the user with this kind of
ambiguities.
Thanks for your suggestion and interest.
Best regards
Matias