Re: Put a name on TChain ?

Nick van Eijndhoven (Nick@phys.uu.nl)
Thu, 23 Apr 1998 09:40:32 +0200 (MET DST)

*** Rene Brun wrote :
>
> Laurent Aphecetche wrote:
> >
> > Hi,
> >
> > Why chains do not have their own name ? It is thus impossible to access
> > them via
> > gROOT->FindObject().
> >
> > Here's my problem. I would like to have a macro that create a chain, and
> > then
> > at the prompt line I would like to play with this chain :
> >
> > void macro(Int_t i1, Int_t i2) {
> > ...
> > TChain* chain = new TChain("thetreename");
> > for (i=i1;i<=i2;i++) chain->Add(filename[i]) ;
> > }
> >
> > root[1] .x macro.C(702,781)
> > root[2] TChain* p=(TChain*)gROOT->FindObject("thetreename");
> > root[3] ...play with p...
> >
> > It seems to me that of course in line 2, it's the tree object that will
> > be found. Why
> > not a chain constructor like TChain::TChain(char* chainname, char*
> > treename) ?
>
> Hi Laurent,
> You are making a good point.
> Currently the TChain constructor has two parameters (treename, title)
> where title is optional. It would have been better to have
> (chainname, treename).
> The problem is that I cannot introduce a second constructor like you
> propose, unless I modify the existing constructor.
> What about the following:
> TChain(const char *treename)
> TChain(const char *chainname, const char *treename)
> This assumes that currently not many people use the TChain constructor
> with two parameters.
> Please comment on this proposal, objections,etc.
>
> Rene Brun
>

Hi Rene,
I would prefer a new member function TTree::SetChainName() or something
like that.
Changing the constructor is like changing the specs of routines like
was sometimes done in the old CERNLIBs and you know what trouble that
gave.

Cheers,

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Dr. Nick van Eijndhoven Department of Subatomic Physics
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