double f(double x)
{
    return x - x*x + x*x*x - x*x*x*x + sin(x*13.)/13.;
}

void example_04a()
{
    TRandom3 rnd;
    
    TH1F *h1 = new TH1F("h1","A Random Histogram",120,-0.1,1.1);
    
    double f_max = 0.;
    for(int i=0;i<1000;i++) {
        double y = f(rnd.Rndm());
        if (y>f_max) f_max = y;
    }
    f_max *= 1.2;
    
    for(int i=0;i<100000;i++) {
        double x,y;
        do {
            x = rnd.Rndm();
            y = rnd.Rndm()*f_max;
        }while (y>f(x));
        
        h1->Fill(x);
    }
    
    h1->SetFillColor(50);
    h1->Draw();
}