TFormula usage in ROOT6 with methods that take std::vector?

ROOT
1

Hi,

I am wondering how I can get a TFormula/TTreeFormula to work in ROOT6 using a function that takes an std::vector as an argument. For example, if I have a class that has a function like this:

double myMethod( const std::vector<int>& myVec ) const;
And I have objects of that class type in my ROOT file. It seems that this is not possible on the ROOT6 command line:

myTTree->Draw("MyClassObj.myMethod({0,3,2})");
I get this kind of error:

Error in <TTreeFormula::DefinedVariable>: Unknown method:myMethod({0,1}) in MyClassObj Error in <TTreeFormula::Compile>: Bad numerical expression : "MyClassObj.myMethod({0,1})" Info in <TSelectorDraw::AbortProcess>: Variable compilation failed: {MyClassObj.myMethod({0,1}),}
I thought that ROOT6 Cling should understand C++11. But maybe not in this context?

I have tried to implement in my class other method signatures, e.g. something like this:

double myMethod2( std::vector<int>&& myVec ) const;
or

double myMethod2( std::initializer_list<int> myVec ) const;
But both gave me the same error.

Thanks already,

Karsten

2

Hi Karsten,

unfortunately TTreeFormula does not take advantage of cling yet. It however is on the todo list for this year:
https://sft.its.cern.ch/jira/browse/ROOT-5083

Once that is there, the power of modern C++ will be yours. :slight_smile:

Cheers,
Benedikt