void leaf_test(string filename){
    
  TChain *chain = new TChain("tree");
  chain->Add(filename.c_str());
  int n = chain->GetEntries();
 
  int bins = 48;

  float data[1][1][bins][bins];
  chain->SetBranchAddress("count_data", data);
  
  uint t=0;
  chain->SetBranchAddress("t", &t);
  
  double x = 0;
  TBranch *bposition = (TBranch*)chain->GetBranch("position");
  TLeafD *lx=(TLeafD*)bposition->GetLeaf("x");
  lx->SetAddress(&x);
   
  for(int it=0; it<n; it++){
    chain->GetEntry(it);
    
    cout <<" t=" <<t <<endl;//works
	cout <<" x=" <<x <<endl;//does not work
  }  
}