Re: [ROOT] Trees or anything else...

From: Rene Brun (Rene.Brun@cern.ch)
Date: Sat Oct 27 2001 - 09:03:59 MEST


Hi Alberto,

On Fri, 26 Oct 2001, Alberto Pulvirenti wrote:

> Hi everybody,
> 
> I have some questions about the TTree and collection classes:
> 
> 1) is it possible to CHANGE the value of a leaf in a selected entry of a 
>    TTree? If so, how it should be done?
> 


If you mean, replacing a leaf value in the Tree in the file, the answer is
NO. This has been discussed many times in this list.


> 2) when using a TTree::Draw() method with a condition, I was unable to 
> return to the initial "unconditioned" list of entries... is there 
> something to do, to reset the TTree and its entry variables (the ones I 
> get wit TTree::GetV1() & similar)

I do not understand this point. Provide a short example that we can
reproduce.

> 
> 3) When using the TObjArray::Remove() or RemoveAt(), does it also delete 
> the object i want to remove? If not, is there another method which does 
> this?

TObjArray::Remove does not delete the object. It only removes a reference
to the object from the list. However, Remove returns a pointer to the
object being removed. So, if you want to remove it from the list and also
delete it, do:
   delete myarray->Remove(object);

> 
> 4) What difference of utilization scopes is there between TObjArray, 
> TList and THashList? And which are, the latter's particular characteristics?

See chapter on collection classes in the Users Guide

> 
> 5) using an "aliroot" session (for who knows it) I wasn't able to clean 
> the RAM when clearing the TObjArrays I used... I must say that, in my 
> class, they are declared as stack data-member (not pointers). Should I 
> declare them in a different way?

Again, not enough information to come with a diagnostic

Rene Brun

> 
> Thanks....
> 
> Alberto
> 
> 
> 



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