TTree : an array of variable length branch : SIZE TYPE

ROOT
1

Hello,

If I create a TTree branch with an array of variable length like this (User’s Guide):

{
TFile *f = new TFile("peter.root","recreate");
Int_t nPhot;
Float_t E[500];
TTree* nEmcPhotons = new TTree("nEmcPhotons","EMC Photons");
nEmcPhotons->Branch("nPhot",&nPhot,"nPhot/I");
nEmcPhotons->Branch("E",E,"E[nPhot]/F");
}

Does “nPhot” have to be of Int_t type?
In all the examples I could find it is Int_t but I am not sure if it is required.

Thank you!!!

Sergei.

2

Yes, if nPhot is used as an array counter in some other branches,
it must be of type integer.

Rene

3

Dear Rene,

It looks like I did not explain the question well enough.
The question really was if nPhot can be any of the following types:

Char_t UChar_t Short_t UShort_t Int_t UInt_t Long64_t ULong64_t

or it can be only of the type Int_t ?

Sergei.

4

It must be Int_t

Rene

5

Dear Rene,

Thank you!!!

So far in almost all my code I was using UInt_t for this purpose, i.e.

UInt_t nPhot; nEmcPhotons->Branch("nPhot",&nPhot,"nPhot/i");

(the nPhot branch has 'i" type too - not “I”).

Does it mean that I should be worried that all those results could be incorrect?

Sergei.