Function with TGraph does not compile

ROOT
1

Dear experts,

I have a function [1] in an external file func.cc. I parse this function to my main.cc file, but when I compile with [2], I got the error message [3]. Do you know what is wrong?
PS: so far, I do not have this problem with histogram.
Regards

[1] func.cc

void setaxis(TGraph *g1, TGraph *g2, int size){ // train, test

  double g1max = TMath::MaxElement(size, g1->GetY());
  double g2max = TMath::MaxElement(size, g2->GetY());
 ...

  g1->SetLineWidth(2);
  g2->SetLineWidth(2);
}

[2] Makefile

ROOTFLAGS = $(shell root-config --cflags)
ROOTLIBS  = $(shell root-config --libs)
CXXFLAGS  = -std=c++0x -I$(CMSSW_RELEASE_BASE)/src/
TMVAFLAGS = -lTMVA -lTMVAGui
GCCFLAG   = -Wall -Wextra

all:$(Target)

do.exe: main.cc ../../myfunc.cc
        g++ -o $@ main.cc $(ROOTFLAGS) $(ROOTLIBS) $(CXXFLAGS) $(TMVAFLAGS) $(GCCFLAG)

[3] Error message

../../func/myfunc.cc: In function 'void setaxis(TGraph*, TGraph*, int)':
../../func/myfunc.cc:421:44: error: invalid use of incomplete type 'class TGraph'
   double g1max = TMath::MaxElement(size, g1->GetY());
                                            ^
In file included from /cvmfs/cms.cern.ch/slc6_amd64_gcc530/cms/cmssw/CMSSW_8_0_20/external/slc6_amd64_gcc530/bin/../../../../../../lcg/root/6.06.00-ikhhed4/include/TMVA/MethodCuts.h:50:0,
                 from main.cc:21:
/cvmfs/cms.cern.ch/slc6_amd64_gcc530/cms/cmssw/CMSSW_8_0_20/external/slc6_amd64_gcc530/bin/../../../../../../lcg/root/6.06.00-ikhhed4/include/TMVA/MethodBase.h:75:7: note: forward declaration of 'class TGraph'
 class TGraph;
       ^
In file included from main.cc:25:0:
../../func/myfunc.cc:422:44: error: invalid use of incomplete type 'class TGraph'
   double g2max = TMath::MaxElement(size, g2->GetY());
                                            ^
In file included from /cvmfs/cms.cern.ch/slc6_amd64_gcc530/cms/cmssw/CMSSW_8_0_20/external/slc6_amd64_gcc530/bin/../../../../../../lcg/root/6.06.00-ikhhed4/include/TMVA/MethodCuts.h:50:0,
                 from main.cc:21:
/cvmfs/cms.cern.ch/slc6_amd64_gcc530/cms/cmssw/CMSSW_8_0_20/external/slc6_amd64_gcc530/bin/../../../../../../lcg/root/6.06.00-ikhhed4/include/TMVA/MethodBase.h:75:7: note: forward declaration of 'class TGraph'
 class TGraph;
2

Dear experts,
may I add that when I run this function in a root macro, it works fine, but it does not work in a main.cc function.
Regards

3

Hi,

You need to #include <TGraph.h>

For interactive ROOT that’s done automatically.

Cheers, Axel.

4

Dear Axel,
you are right, thank you.
Regards