hey i am curious on the actual code you written. Cause i want to know if doing that is faster than copying an item to a container and like iterate over that.

template
    <
       class T, class U,
       template <typename ELEM, typename = std::allocator<ELEM> >
       class CONT
    >
CONT<T> getKeys(const boost::unordered_map<T, U>& data)
{
    CONT<T> retCont;
    typedef typename boost::unordered_map<T, U>::value_type value_type;
    BOOST_FOREACH(value_type val, data)
    {
        retCont.push_back(val.first);
    }
    return retCont;
}

Note i am using keys instead of value but concept is the same.

On Nov 30, 2007 1:59 AM, John Kiopela <john.kiopela@gmail.com> wrote:

Thanks a lot both. Transform Iterator did the trick.

 

Kind regards,

 

John

 

On Nov 29, 2007 9:04 PM, Niels Aan de Brugh <niels@invalid.org> wrote:

On 2007-11-29, John Kiopela <john.kiopela@gmail.com> wrote:
>
> I have been browsing through the docs, but I couldn't find anything useful.
> Does Boost have a std::map<K, V>::iterator adaptor which iterates over the
> values of the map only.

 

What about using a boost::transform_iterator<>? Docs at:

  http://boost.org/libs/iterator/doc/transform_iterator.html

You'd have to supply it with a function object that returns the 'second'
member variable of the pair, e.g.

 struct get_pair_value
 {
     template< typename K, typename V >
     V operator()( std::pair< K, V > const& pr )
     { return pr.second; }
 };

Or you could use Boost.Lambda.

N.

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