The following program handles regular directories in a file, or folders (ugh).
Most histograms are added bin by bin.

For scaler events it is convenient to see the counts as a function of time (ala
sclaer history plots in mhttpd).  If the histogram looks like a scaler plot versus
time, then new bins are added on to the end (or into the middle!) of the histogram.

All different versions of cuts are kept.

TTrees are not explicitly supported, so probably don't do the right thing...

John.

> Dear MIDAS users,
> 
> I want to add several .root-files produced by the MIDAS analyzer, in a fast 
> and convenient way. ROOT's hadd fails because it does not know how to treat 
> TFolders. I guess this problem is not unique to me, so I hope that somebody of 
> you might already have found a solution.
> 
> Why don't I just run "analyzer -r 1 10000"?
> We have taken lots of runs under (rapidly) varying conditions, so it would be 
> lots of "-r". And the analysis is quite involved, so rerunning all data takes 
> about one hour on a fast PC making this quite painful.
> Therefore, I would like to rerun all data only once, and then add the result 
> files depending on different criteria.
> 
> Of course, I tried to write a script that does the adding. But somehow it is 
> incredibly slow. And I am not the Master Of C++, too.
> 
> Is there any deeper reason for MIDAS using TFolders, not TDirectorys? ROOT's 
> hadd can treat TDirectory. Can I simply patch "my" MIDAS? Is there general 
> interest in a change like this? (Does anyone have experience with the speed of 
> hadd?)
> 
> Looking forward to comments from the Forum.
> 
> Cheers,
> 
> Randolf