Re: [ROOT] variable-size array of compiled class in a branch?

From: Carlos Muņoz Camacho (
Date: Tue Jun 15 2004 - 15:48:02 MEST


I thought only variable size arrays of simple types were allowed (p.177 of
User's Guide). Is this no longer a restriction ?

Actually when I modify your read.C as follows to print out the data
members of foo, it doesn't seem to work :

   Foo *foo=0;
   TFile f("xxxxx.root");
   Int_t nentries=tree.GetEntries();
   Int_t nb=0;
   for (Int_t i=0;i<nentries;i++) {
      nb += tree.GetEntry(i);


On Mon, 14 Jun 2004, Rene Brun wrote:

>See the tar file in attachement with your classes modified to run
>correctly. I also added a small reader example.
>Rene Brun
>Yiqun Wang wrote:
>> Hi, ROOTers:
>> In Guide (3.10), I see one can have a variable-size array for a simple
>> type (Int_t, Float_t, etc.). Can we do that for a compiled class? I tried
>> the attached program, but got many errors (mismatched size) when reading
>> the root file in an interactive session. Any suggestions?
>> The motivation is to save disk space. Events I have may have interesting
>> data in only one module, or multiple modules. If possible, I don't want to
>> write all modules when some of them do not contain interesting data.
>> To run my simplied example, untar the attached "test.tar.gz" in an empty
>> directory, and run "make all". After that, run "./test" and generate the
>> root file "xxxxx.root". This file has one tree "tree", which contains a
>> branch "foo" (of class "Foo"). The leaf "modules" is the variable-size
>> array of compiled class "Bar".
>> Thanks!
>> Yiqun Wang
>>   --------------------------------------------------------------------------------
>>                   Name: test.tar.gz
>>    test.tar.gz    Type: Unix Tape Archive (application/x-tar)
>>               Encoding: base64

This archive was generated by hypermail 2b29 : Sun Jan 02 2005 - 05:50:08 MET