Toby Burnett

• We long ago agreed to allow fixed length vectors in our
ROOT tuples
• ROOT supports this, and ntupleWriterSvc was modified to accommodate this in August 2004.
– A client specifies an array simply by appending ‘[ n ]’ to the name, and passing the address a vector of length n
– ROOT expressions support indexing with name [ i ], where i =0..
n -1
• However:
– Bill’s application that converts a ROOT tree to an ascii table does not allow for this extension

• As a (significant) example, consider the PtPos variable in
MeritTuple
• The following line of CINT or C++,
MeritTuple->Branch("PtPosBranch",
MeritTuple->GetLeaf("PtPos")->GetValuePointer(),
"PtPosX:PtPosY:PtPosZ/F"); creates a new branch with 3 leaves defining aliases for the components.
Demonstration at right: PtPos[0] is the same as PtPosX.

• There are many 3-vectors in the current MeritTuple.
• We consider replacing, or adding as an alias, preliminary to replacing, each component description with the root name.