Hi Birger,
Let see if I understand correctly your request.
- you are requesting an operator [] to get the ith bit in a TBits
instead of calling the function TestBitNumber().
That is quite easy to implement. I propose in this case
a read only operator [].
- you want to do mytree.Draw("myEventBits");
This will automatically loop on all your events and filling
an hitogram with as many channels as there are bits in TBits
and where the bin count is incremented by 1 or the specified weight
for each event where the corresponding bit is set.
This requires a bit more work, but I agree would be a nice addition.
Rene
On Thu, 31 Oct 2002, Birger Koblitz wrote:
> Hi Rene,
>
> I think Ursula Berthon already talked to you about this at the
> Root-Meeting:
>
> Within H1 we would like to be able to put bit-arrays into our HAT tree
> which should be accessible using only a browser and which is used for
> event selection. Currently TBits allows to use the member function
> TestBitNumber() which is quite inconvenient if it comes to a selection of
> a large number of status bits e.g. to check if the quality of an event is
> good. This could easily go over the maximum selection length of a tree.
> Therefore it would be nice if one could simply use bits[i] to check the
> ith bit in TBits bits. In addition it would be nice if one could view a
> bit-array in a TBrowser. It should show a histogram over the bits and the
> number of entries per bit. Currently fAllBits shows the entries (in 2^i
> form) for the lowest byte. I think this is not really useful.
>
> In the moment we are using byte-arrays which at least allow to use the []
> operator and allow us to inspect one bit with the TBrowser. H1 would be
> very intersted to move to TBits because currently the bit-arrays make up
> most of our HAT ntuple, we would be even willing to move to a newer
> root-version ;-)
>
> Cheers,
> Birger
>
> ------------------------------------------------------------
> Birger Koblitz koblitz@mail.desy.de
> MPI für Physik
> c/o DESY-FH1 Tel: +49 40 8998-2431
> Notkestr. 85 Fax: +49 40 8998-3094
> D-22603 HAMBURG
>
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