Re: Copying from maps to lists or vectors
On Apr 17, 8:55 pm, pallav <pallavgu...@gmail.com> wrote:
I have a map like this:
typedef boost::shared_ptr<Node> NodePtr;
typedef std::vector<NodePtr> NodeVecPtr;
typedef std::map<std::string, NodePtr> NodeMap;
typedef std::map<std:string, NodePtr>::iterator NodeMapItr;
NodeMap nmap;
In my classes, I often find myself copying the second arguments of
maps to lists/vectors like this.
NodeVecPtr nodes;
for (NodeMapItr itr = nmap.begin(); itr != nmap.end(); ++itr)
nodes.push_back(itr->second);
I may also have node be a list of NodePtrs as opposed to vectors. I'm
wondering if there is some standard STL routines, I can use to try to
reduce this kind of code being repeated. I now std::copy() exists but
it takes iterators. But since I'm dealing with maps, I'm not sure how
to pass the second value as an iterator. There is also
std::transform() but that also works with iterators.
I've been searching the web, and found stuff like boost::bind and
boost::iterator_adaptors that might work but I'm trying to read up the
documentation to figure out the syntax.
If somebody can help me in showing how I could accomplish this using
STL/boost features, this will be helpful. Thanks for you time.
Wouldn't something like the following work:
template< typename Map >
struct ValueFromMap
: public std::unary_function< typename Map::value_type,
typename Map::mapped_type >
{
typename Map::mapped_type operator()(
typename Map::value_type const&
elem ) const
{
return elem.second ;
}
} ;
typedef boost::transform_iterator< ValueFromMap< NodeMap >,
NodeMap::const_iterator >
ValueIter ;
(I tried it with a std::map< std::string, int >, and it seemed
to work.)
--
James Kanze (GABI Software) email:james.kanze@gmail.com
Conseils en informatique orient=E9e objet/
Beratung in objektorientierter Datenverarbeitung
9 place S=E9mard, 78210 St.-Cyr-l'=C9cole, France, +33 (0)1 30 23 00 34