I've a set of trees (e.g. a set of identically structured XML documents) and I want to be able to return a reference to a certain position in the tree. My test tree node is [1] below, with a test tree [2]. I think I can solve this with boost::function and boost::lambda. E.g. this works: boost::function1<int,Node&> best2; best2=bind(&Node::value2,_1); std::cout<<"best2(root)="<<best2(root)<<"\n"; std::cout<<"best2(child[0])="<<best2(root.children[0])<<"\n"; I also need to be able to treat "number of children" the same way I can treat value1 or value2. I've now worked this out as: best2=bind(&std::vector<Node>::size,bind(&Node::children,_1)); Going strong, but now I want to refer to the "value1 of the first child". Following the patterns of the previous ones I thought it would be: best2=bind(&Node::value2, bind( &std::vector<Node>::at, //Ask for an element bind(&Node::children,_1), //Get the vector object 0 ) //Ask for element zero ); That fails with a short error message [3], which is so rare when dealing with BLL that I thought I might be able to understand it, but no, I couldn't work out which bit it didn't like. Can anyone help? Also, is there any limit to how deep I can nest these binds? I think I'm going to need 3 more levels, but it would be useful to know if it is unlimited. Darren [1]: class Node{ public: std::vector<Node> children; int value1,value2; public: Node(int v1,int v2):value1(v1),value2(v2){} friend std::ostream& operator<<(std::ostream& s,const Node& obj){ s<<"value1="<<obj.value1<<",value2="<<obj.value2<<",children.size="<<obj.children.size()<<"\n"; return s; } }; [2] Example usage: Node root(1,111); root.children.push_back(Node(2,222)); std::cout<<root<<root.children[0]; [3]: function.cpp: In function `int main(int, char**)': function.cpp:69: no matching function for call to `bind(<unknown type>, const boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2, boost::lambda::function_action<2, boost::lambda::detail::unspecified> >, boost::tuples::tuple<std::vector<Node, std::allocator<Node> > Node::*, const boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > >, int)'