Re: [Boost-users] Pointer to objects in Boost.MultiIndex

Amit Prakash Ambasta writes:

Consider the following code snippet:

[...]

struct LinkList;

struct LinkList {     size_t index;     LinkList* parent;     LinkList(size_t index, LinkList* parent) : index(index), parent(parent) {} };

struct llindex {};

typedef ordered_unique< tag<llindex>, member

...

LinkListIndex; typedef boost::multi_index_container< LinkList, indexed_by<LinkListIndex> IndexedLinkList;

[...]

int main() {     IndexedLinkList ill;     auto &index_ll = ill.get<0>();

    ill.insert(LinkList{0, nullptr});     ill.insert(LinkList{1, (LinkList*)(&(*index_ll.find(0)))});     ill.insert(LinkList{2, (LinkList*)(&(*index_ll.find(0)))});     ill.insert(LinkList{3, (LinkList*)(&(*index_ll.find(2)))});

    show(ill);     return 0; }

Would (LinkList*)(&(*index__ll.find(value))) be the recommended way to fetch the pointer to parent?

Depends on the context. If you're inserting the elements in sequential ordering (i.e. the newly inserted element is linked to the last one), then this is faster as you don't do any lookup: auto it=ill.insert(LinkList{0, nullptr}).first; it=ill.insert(LinkList{1, (LinkList*)(&*it)}).first; it=ill.insert(LinkList{2, (LinkList*)(&*it)}).first; it=ill.insert(LinkList{3, (LinkList*)(&*it)}).first; Maybe you can provide some more info on the purpose of the structure you're buliding here? Boost.MultiIndex might help further. For instance, this is a list-like structure quicky searchable by index: typedef boost::multi_index_container< node, indexed_by< sequenced<>, ordered_unique> > > IndexedLinkList; void show(const IndexedLinkList& ill) { for(auto begin=ill.begin(),first=begin,last=ill.end(); first!=last;++first){ if(first!=begin){ auto prior=first;--prior; std::cout<<"Index<"<<first->index<<">: " <<prior->index<: " <<"NULL"<