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    "# tree112_copy\n",
    "Example of Root macro to copy a subset of a Tree to a new Tree, selecting entries.\n",
    "\n",
    "Only selected entries are copied to the new Tree.\n",
    "The input file has been generated by the program in `$ROOTSYS/test/Event`\n",
    "with `Event 1000 1 99 1`\n",
    "\n",
    "\n",
    "\n",
    "\n",
    "**Author:** Rene Brun  \n",
    "<i><small>This notebook tutorial was automatically generated with <a href= \"https://github.com/root-project/root/blob/master/documentation/doxygen/converttonotebook.py\">ROOTBOOK-izer</a> from the macro found in the ROOT repository  on Tuesday, May 19, 2026 at 08:18 PM.</small></i>"
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   "source": [
    "#ifdef ACTUAL_RUN  // -------- Second pass: dictionary already built --------\n",
    "\n",
    "#include \"./Event.h\"  // now safe to include Event, its dictionary is loaded\n",
    "\n",
    "#else  // -------- First pass: build dictionary + rerun macro --------"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "c71e76b2",
   "metadata": {},
   "source": [
    " Definition of a helper function: "
   ]
  },
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   "execution_count": 2,
   "id": "3eda1295",
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    }
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   "outputs": [
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      "input_line_53:9:4: error: unknown type name 'Event'\n",
      "   Event *event = nullptr;\n",
      "   ^\n"
     ]
    }
   ],
   "source": [
    "%%cpp -d\n",
    "void run()\n",
    "{\n",
    "   TFile oldfile(\"tree108.root\");\n",
    "   TTree *oldtree;\n",
    "   oldfile.GetObject(\"t4\", oldtree);\n",
    "\n",
    "   const auto nentries = oldtree->GetEntries();\n",
    "\n",
    "   Event *event = nullptr;\n",
    "   oldtree->SetBranchAddress(\"event_split\", &event);\n",
    "\n",
    "   // Create a new file + a clone of old tree in new file\n",
    "   TFile newfile(\"tree112.root\", \"recreate\");\n",
    "   auto newtree = oldtree->CloneTree(0);\n",
    "\n",
    "   for (auto i : ROOT::TSeqI(nentries)) {\n",
    "      oldtree->GetEntry(i);\n",
    "      if (event->GetNtrack() > 605)\n",
    "         newtree->Fill();\n",
    "      event->Clear();\n",
    "   }\n",
    "\n",
    "   newtree->Print();\n",
    "   newfile.Write();\n",
    "}"
   ]
  },
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   "outputs": [
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      "Error in <TApplication::ProcessLine>: macro /github/home/ROOT-CI/build/tutorials/io/tree/Event.cxx not found in path .:/github/home/ROOT-CI/build/macros\n",
      "input_line_56:1:10: fatal error: 'input_line_54' file not found\n",
      "#include \"input_line_54\"\n",
      "         ^~~~~~~~~~~~~~~\n",
      "input_line_58:2:3: error: use of undeclared identifier 'run'\n",
      " (run())\n",
      "  ^\n",
      "Error in <HandleInterpreterException>: Error evaluating expression (run())\n",
      "Execution of your code was aborted.\n"
     ]
    }
   ],
   "source": [
    "TString tutdir = gROOT->GetTutorialDir();\n",
    "gROOT->ProcessLine(\".L \" + tutdir + \"/io/tree/Event.cxx+\");\n",
    "gROOT->ProcessLine(\"#define ACTUAL_RUN yes\");\n",
    "gROOT->ProcessLine(\"#include \\\"\" __FILE__ \"\\\"\");\n",
    "gROOT->ProcessLine(\"run()\");"
   ]
  }
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