RE: [ROOT] My procedure using TExec is wrong ?

From: Philippe Canal (pcanal@fnal.gov)
Date: Tue Dec 04 2001 - 19:45:18 MET 

> Error in <TApplication::TApplication>: only one instance of TApplication allowed

In your code:

>  gROOT->ProcessLine(".L py.C");
>  TApplication *app = new TApplication("app", &argc, argv);

The creation of TApplication you be done as early as possible and
definitively before calling gROOT->ProcessLine:

int main (int argc, char** argv) {  
  TApplication *app = new TApplication("app", &argc, argv);
  gROOT->ProcessLine(".L py.C");

Since 'h' is being defined in your compiled code, ProjectionXY does
not have automatic access to it.  You could use a compiled version
of ProjectionXY (doing .L py.C++ and make sure that h, h1_px and
h2_py are defined as extern references inside py.C) or you need to
declare h, h1_px and h2_py to the interpreter using something 
similar to:

  gROOT->ProcessLine(".L define.C");

with define.C
// start define.C
#include <TH1.h>
#include <TH2.h>
extern TH2F *h;
extern TH1D *h1_px, *h1_py;
// end of define.C

Cheers,
Philippe.

-----Original Message-----
From: owner-roottalk@pcroot.cern.ch
[mailto:owner-roottalk@pcroot.cern.ch]On Behalf Of Harufumi Tsuchiya
Sent: Tuesday, December 04, 2001 2:13 AM
To: brun@pcbrun.cern.ch
Cc: roottalk@pcroot.cern.ch
Subject: Re: [ROOT] My procedure using TExec is wrong ?


Thank you so much for your quick reply.

Using your attached programs in previous mail, 
I modified one of the programs (pym.C) like bottom of
this mail (mod_pym.C) for compiling via g++. 
I certainly could do what I want to do. But, I got new error
message.

Error in <TApplication::TApplication>: only one instance of TApplication allowed

What is the meaning ?

And also I have one more question.
In fact, ProjectionXY is defiend in my origianl main program and
h , other histograms(h1_px, h1_py) and pad are
also defined in the top of the main program like below.
This procedure is wrong ?
In such a case that I want to do, Must I separate ProjectionXY in atnoter
file in order to use gROOT->ProcessLine() ?

TH2F *h;
TH1F *h1_px, *h1_py;
TPad *pad[4];
int main ( int argc, char** argv ) {
     :
     :
}

void ProjectionXY() {
     :
     :
}

Thank you,

Harufumi Tsuchiya

-------------------------
mod_pym.C
-------------------------
#include <TROOT.h>
#include <TH1.h>
#include <TH2.h>
#include <TExec.h>
#include <TCanvas.h>
#include <TFile.h>
#include <TApplication.h>

TH2F *h;
TH1D *h1_px, *h1_py;

int main (int argc, char** argv) {
  
  gROOT->ProcessLine(".L py.C");

  TApplication *app = new TApplication("app", &argc, argv);

  TExec *ex_proj = new TExec("ex_proj", "ProjectionXY()");
  TFile f("hsimple.root");
  h = (TH2F*)gDirectory->Get("hpxpy");
  h->GetListOfFunctions()->Add(ex_proj);
  h1_px = 0; h1_py = 0;
  TCanvas c1("c1");
  c1.Divide(2,2);
  c1.cd(1);
  h->Draw("colz");
  
  app->Run();
}

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