Re: nested iterators

Fons Rademakers (Fons.Rademakers@cern.ch)
Thu, 11 Mar 1999 16:12:04 +0000

The current way is the only portable way (since container independent).
However, creating a TIter (on the stack) causes the
allocation/deallocation
of a container specific iterator on the stack (via new/delete). If the
innerloop
is called millions of times you can better try container specific
alternatives.
For example:

leafList = branch->GetListOfLeaves();
int entries = leafList->GetEntriesFast();
for (int i = 0; i < entries; i++) {
leaf = (TLeaf*) leafList->UncheckedAt(i);
// stuff
}

Cheers, Fons.

Sean Kelly wrote:
>
> Hi Rooters
>
> My question is with regards to the correct way to implement nested
> iterators.
>
> In the code fragment below, it seems that inner loop iterator is
> created many times, when all I really want to do is to reset it to
> the new value of leafList.
>
> Thanks for any advice.
>
> Sean Kelly
>
> TObjArray *branchList = ntuple->TTree::GetListOfBranches();
> TObjArray *leafList;
>
> TIter nextBranch(branchList);
> while ( branch = (TBranch*) nextBranch() ) {
> leafList = branch->GetListOfLeaves();
> TIter nextLeaf(leafList);
> while ( leaf = (TLeaf*) nextLeaf() ) {
>
> // stuff
>
> }
> }

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