CGAL users discussion list

[David Scriven <>]

Given a set, D, of (x, y, z) triplets in Euclidean 3 space, I want identify groups K1..n that have the following simple characteristic:

For every tj that is a member of Ki  there exists a tm (m != j) s.t. Euclidean dist(tj, tm)  < value. 

Looking through CGAL it seemed that the NN incremental search would help me identify these groups and I modified the example given:

........

int valsq = value*value;

// A functor that returns true, iff the distance of a 3D point is greater than value^2
struct X_gt_valsq {
bool operator()(const NN_iterator& it) { return ((*it).second > valsq); }
};

typedef CGAL::Filter_iterator<NN_iterator, X_gt_valsq> NN_gtvalsq_iterator;

std::list<Point_3> coords;
......// add points.....

Tree tree(coords.begin(), coords.end());

Point_3 query(x,y,z); // some member of coords

NN_incremental_search NN(tree, query);
NN_gtvalsq_iterator it(NN.end(), X_gt_valsq(), NN.begin()), end(NN.end(), X_gt_valsq());
......
while(it!=end)
{
   std::cout << (*it).first << " at squared distance = " << (*it).second << std::endl;
   it++;
}

which works, but I can't see how to use the information from the iterator it (which is an input_iterator) to identify which members of coords are with a NN distance of < valsq so that I can delete them from the coords dataset to start the next search.  Any advice?