void makeFunctions(){
gROOT->LoadMacro("myfunctions.C");
//
//very simple TF1 and TF2 examples
//
// Load user-defined functions

// 
TF1 *f1 = new TF1("func1D",func1D,0,10,2);
f1->SetParameters(2,1);
TCanvas *c1 = new TCanvas("c1","TF1 example",200,10,600,400);
//can be directly called as a C++ function;
cout << "the value of f1(1.) is:" << f1(1.)<< endl;
f1->Draw();


TF2 *f2 = new TF2("func2Dname",func2D,-3,3,-3,3,3);
f2->SetParameters(100,0,1);
TCanvas *c2 = new TCanvas("c2","TF2 example",200,10,600,400);
cout << "the value of f2(1.,2.) is:" << func2Dname(1.,2.)<< endl;
f2->Draw("surf");

TFile *file = new TFile("functions.root","recreate");
f2->Write();
f1->Write();
file->Close();
}