void example();
// Double_t customFunction(Double_t *x,Double_t *par);
double customFunction(double x);

void example(){

	TCanvas * myCanvas = new TCanvas();
	// TF1* myTF1 = new TF1("myTF1",customFunction,0., 100.);
	TF1* myTF1 = new TF1("myTF1","customFunction(x)",0., 100.);
	myTF1->Draw();
	myCanvas->Update();
	myCanvas->SaveAs("exampleCanvas.C");
}

// Double_t customFunction(Double_t *x,Double_t *par){return 2*x[0];}
double customFunction(double x){return 2*x;}