/// \file

/// \ingroup tutorial_math

/// \notebook

/// Tutorial illustrating how creating a TF1 class using functor or class member functions

///

/// can be run with:

///

/// ~~~{.cpp}

/// root > .x exampleFunctor.C

/// root > .x exampleFunctor.C+ with ACLIC

/// ~~~

///

/// \macro_image

/// \macro_code

///

/// \author Lorenzo Moneta

#include "TF1.h"

#include "TMath.h"

#include "TLegend.h"

double MyFunc (double *x, double *p ) {

return TMath::Gaus(x[0],p[0],p[1] );

}

// function object (functor)

struct MyDerivFunc {

MyDerivFunc(TF1 * f): fFunc(f) {}

double operator() (double *x, double * ) const {

return fFunc->Derivative(*x);

}

TF1 * fFunc;

};

// function class with a member function

struct MyIntegFunc {

MyIntegFunc(TF1 * f): fFunc(f) {}

double Integral (double *x, double * ) const {

double a = fFunc->GetXmin();

return fFunc->Integral(a, *x);

}

TF1 * fFunc;

};

void exampleFunctor() {

double xmin = -10; double xmax = 10;

// create TF1 using a free C function

TF1 * f1 = new TF1("f1",MyFunc,xmin,xmax,2);

f1->SetParameters(0.,1.);

f1->SetMaximum(3); f1->SetMinimum(-1);

f1->Draw();

// Derivative function

// example to create TF1 using a functor

// in order to work with interpreter the function object must be created and lived all time for all time

// of the TF1. In compiled mode, the function object can be passed by value (recommended) and there

// is also no need to specify the type of the function class. Example is as follows:

//

// `TF1 * f2 = new TF1("f2",MyDerivFunc(f1), xmin, xmax,0); // only for C++ compiled mode`

MyDerivFunc * deriv = new MyDerivFunc(f1);

TF1 * f2 = new TF1("f2",deriv, xmin, xmax, 0);

f2->SetLineColor(kBlue);

f2->Draw("same");

// integral function

// example to create a TF1 using a member function of a user class

// in order to work with interpreter the function object must be created and lived all time for all time

// of the TF1. In compiled mode there is no need to specify the type of the function class and the name

// of the member function

//

// `TF1 * f3 = new TF1("f3",intg,&MyIntegFunc::Integral,xmin,xmax, 0); // only for C++ compiled mode`

MyIntegFunc * intg = new MyIntegFunc(f1);

TF1 * f3 = new TF1("f3",intg,&MyIntegFunc::Integral, xmin, xmax, 0);

f3->SetLineColor(kRed);

f3->Draw("same");

TLegend * l = new TLegend(0.78, 0.25, 0.97 ,0.45);

l->AddEntry(f1, "Func");

l->AddEntry(f2, "Deriv.");

l->AddEntry(f3, "Integral");

l->Draw();

}