Difference Between TEntryList and TEventList

The difference between TEntryList and TEventList is not easy to discern.

https://root.cern.ch/doc/master/classTEventList.html says:
" A TEventList object is a list of selected events (entries) in a TTree." So already it seems “events” and “entries” are equivalent.

Meanwhile https://root.cern.ch/doc/master/classTEntryList.html immediately starts talking about kBlockSize and internal storage. Later on it says they are different but the links only show you TTree/TChain methods that transform a TEntryList into a TEventList (I think?)

I couldn’t find references in the manuals/tutorials telling you to use one or the other.

I found a forum post from 2017 saying that TEntryList supercedes TEventList: How to select and process events from a TTree that pass a graphical cut

If this is indeed the case, then there should be a prominent message at the top each reference page telling you this.

TEntryList will be better in allmost all cases (except cases where there is only a small number of entries selected). The main change was going from a simple list/array of selected entries (TEventList) to a more complex structure that takes less spaces for dense selections and handles very large number of selections (TEntryList).


So already it seems “events” and “entries” are equivalent.


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