ROOT Course. Vincenzo Vitale, Dip. Fisica and INFN Roma 2

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1 ROOT Course Vincenzo Vitale, Dip. Fisica and INFN Roma 2

2 OUTLINE Object-Oriented programming Procedural and OO paradigms Fundamental Concepts A ROOT class Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 2

3 Object-Oriented Programming Object-Oriented programming (OOP) is a programming PARADIGM It is also dubbed class-based or prototype-based programming C++ supports multiple paradigms Functional programming = a sequence of stateless function evaluation Object-Oriented programming = collection of interacting objects Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 3

4 Procedural Paradigm PROCEDURE 1 MAIN LOOP PROCEDURE 2 PROCEDURE 3 Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 4

5 Procedural Paradigm Unreadable for large complex code Difficult to manage Difficult for modelling real world object complexity Difficulty to reuse code Data are not protected by accidental over-writing Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 5

6 Obj. Oriented Paradigm DATA Interface OBJECT PROGRAM DATA Interface OBJECT MESSAGE DATA Interface OBJECT DATA Interface OBJECT Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 6

7 Obj. Oriented Paradigm Code can be easily reused Project can be extended by means of class derivation Class allow modelling of real world objects Complexity of coding is reduced Data are protected by accidental operation All major modern programming languages support obj. oriented programming (at the end also Fortran2003!) Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 7

8 Fundamental Concepts Class Object Method Inheritance Encapsulation Polymorphism Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 8

9 Class CLASS = expanded concept of data structure It can hold both data (data members) and function (methods) used as a model to create objects. class Crectangle { int x, y; public: void set_values (int,int); int area (){return (x*y);} } void CRectangle::set_values (int a, int b) { x = a; y = b; } Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 9

10 Object OBJECT = an instance of a class An object has a state (value of data members) An object has a behaviour Int number; Crectangle rect; Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 10

11 Method Methods are functions which can act on data members Class Crectangle {... void set_values (int x, int y) int area () {return (x*y);} }; void CRectangle::set_values (int a, int b) {x = a; y = b; } int main () { CRectangle rect, rectb; rect.set_values (3,4); rectb.set_values(4,5); cout << "area: " << rect.area(); return 0; } Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 11

12 Polymorphism Ability of objects belonging to different types to respond to method calls of the same name Each object responds in accordance to its behavior class CVector { public: int x,y; CVector::CVector (int a, int b) { x = a; y = b; } }; CVector (int,int); CVector operator + (Cvector); } CVector CVector::operator+ (CVector param) { CVector temp; temp.x = x + param.x; temp.y = y + param.y; return (temp); Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 12

13 Inheritance A CLASS can be derived by an already existing one (parent CLASS) The derived CLASS inherits parent methods class CPolygon { protected: int width, height; public: void set_values (int a, int b { width=a; height=b;} }; class CRectangle: public CPolygon { public: int area () { return (width * height); } }; Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 13

14 Encapsulation Encapsulation defines the CLASS-CLASS interaction Method of a CLASS are permitted only to specific other classes Method can be defined as PUBLIC, PROTECTED and PRIVATE Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 14

15 An example of ROOT class The TF1 CLASS Constructor Draw method Formula Draw options Title Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 15

16 An example of ROOT class class TF1: public TFormula, public TAttLine, public TAttFill, public TAttMarker Function Members (Methods) public : TF1() TF1(const TF1& f1)... virtual void Draw(Option_t* option = "")... protected:... Double_t TFormula::EvalParFast(const Double_t* x, const Double_t* params) Double_t TFormula::EvalPrimitive(const Double_t* x, const Double_t* params)... Vincenzo Vitale, Astro & Particle Physics SW, June 2008, Roma 16

Object Oriented Programming. A class is an expanded concept of a data structure: instead of holding only data, it can hold both data and functions.

Object Oriented Programming. A class is an expanded concept of a data structure: instead of holding only data, it can hold both data and functions. Classes (I) Object Oriented Programming A class is an expanded concept of a data structure: instead of holding only data, it can hold both data and functions. An object is an instantiation of a class.