marek.vondrak
8/30/2008 12:03:00 AM
On Aug 29, 8:17 am, Leandro Melo <ltcm...@gmail.com> wrote:
> On 28 ago, 16:30, marek.vond...@gmail.com wrote:
>
> > Hi,
> > I am wondering if there are any functional differences between SGI's
> > hash_map and tr1's unordered_map. Can these two containers be
> > interchanged? What would it take to switch from hash_map to
> > unordered_map? Thank you.
> It's not clear to me what exactly is your doubt. Just like SGI's
> hash_map the "new" unordered_map is also based on a hash table. Since
> hash_map (and hash_set, hash_multimap, hash_multiset) is not standard,
> several compilers have provided their own implementation (GCC's for
> example is based on SGI's hash map).
Right. GCC provides SGI style hash_map under the name
__gnu_cxx::hash_map, MSVC with Dinkumware C++ library under the name
stdext::hash_map. The Dinkumware version differs from the SGI's
hash_map in certain minor details, but wrappers can be written so that
it would behave as SGI's hash_map. Now, my question is if the same
thing can be easily done with unordered_map, such that the wrapper
would have the same external interface like SGI's hash_map and provide
same guarantees about iterator invalidations, etc. I have an existing
code base that assumes that there is a class ext::hash_map that has
the semantics of SGI hash_map and that maps either to
__gnu_cxx::hash_map, SGI's hash_map, STLPort's hash_map or a wrapper
around stdext::hash_map. I would like to extend this so it could be
mapped to tr1::unordered_map as well.
-Marek