[Boost-users] Re: boost::indirect_iterator

Matthias Kaeppler writes:

Consider this code:

vector<int> coll; // ... push back some values vector ptrcoll; // ... push back pointers to the values of coll

indirect_iterator< vector::iterator > begin(ptrcoll.begin()),

Careful; vector iterators are not neccessarily pointers.

end(ptrcoll.end());

sort( begin, end, less<int> );

--

My question: After the sort statement, coll is sorted, right? (and ptrcoll is not). However, I need to sort a vector of pointers according to a predicate which applies to non-pointers. In this case, I want to sort ptrcoll, according to the less-relation on the pointees in coll.

How can I achieve that?

struct indirect_less { template <class It> bool operator()(It i1, It i2) const { typedef typename std::iterator_traits<It>::value_type value_type; return std::less()(i1,i2); } }; sort(ptrcoll.begin(), ptrcoll.end, indirect_less()); HTH, -- Dave Abrahams Boost Consulting www.boost-consulting.com