Ne zaman operator overloading yapilir. Operator Overloading

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1 Operator Overloading Operator overloading, bir operator e standard anlami haricinde yeni anlamlar vermek Overloaded operator giris olarak aldigi operand (parameter ) larin type ine gore anlam kazanir Ornek: standard matematikte, + ve integers, reals, vectors, complex numbers, matrices, vb icin tanimlanir C++ da, << operator oveload edilmistir 1. Anlam: stream insertion operator 2. anlam: Bitwise left-shift operator 12/10/2004 Nesneye Yonelik Programlama 8.1 Ne zaman operator overloading yapilir Operator overloading function call ve member function call larinin notasyonunu kolaylastirir Ornek: Color3 = mix (Color1, Color2); yerine Color3= Color1 + Color2; yazilabilir burada + color lar icin tanimlanmistir Operator overloading ayni zamanda kullanici tarafindan tanimlanmis yeni typeler le built-in type ler arasindaki analogy i pekistirmek icin kullanilirlar Ornek: << ve >> operatorleri user-defined type lar icn output input islemleri icin tanimlanabilir 12/10/2004 Nesneye Yonelik Programlama 8.2 Overload edilebilen C++ Operator leri Assignment operator ve stream operators =, <<, >> Arithmetic operators +, -, *, /, %, +=, -=, *=, /=, %= Increment and decrement operators ++, -- Logical operators!, &&,, <<, >> Bitwise logical operators ~, ^, &,, ^=, &=, = Relational and equality operators <, >, <=, >=, ==,!= Dynamicmemory allocation operators new, delete, new [ ], delete [ ] Other operators ( ), [ ], ->, the comma operator (, ) 12/10/2004 Nesneye Yonelik Programlama 8.3 Overload edilemeyen operator ler. Dot member access operator.* Dot member access using pointer :: scope resolution operator?: ternary conditional operator sizeof 12/10/2004 Nesneye Yonelik Programlama 8.4

2 C++ da operator ler nasil overload edilirler Syntax: <return_type> <class_name>::operator# (<parameters>) { <function body that defines operator # > Semantics: Operator # user-defined class (ismi class_name) in objectleri icin yeniden tanimlanir <parameters> tipik olarak <class_name> tipinde bir giris parameter ve <return_type> tipik olarak <class_name> tipinde geri donen degerin tipini gosterir 12/10/2004 Nesneye Yonelik Programlama 8.5 Ornek // Contents of the header file point.h class Point { public: void setpoint (int i, int j, int k); // define a default constructor Point (int i=0, int j=0, int k=0 ) { setpoint (i,j,k); Point operator+ ( Point p) ; Point operator= (Point p); void displaypoint ( Point P ) const; private: int x,y,z; // 3-D coordinates 12/10/2004 Nesneye Yonelik Programlama 8.6 // start of file point.cpp #include <iostream> #include point.h void Point::setPoint (int I, int j, int k) { x = i; y = j; z = k; void Point::displayPoint ( Point p) const { cout << ( << x <<, << y <<, << z << ) ; Point Point::operator+ (Point p) { Point result; result.x = x + p.x; result.y = y + p.y; result.z = z + p.z; return result; 12/10/2004 Nesneye Yonelik Programlama /10/2004 Nesneye Yonelik Programlama 8.8 Point Point::operator= (Point p) { x = p.x; y = p.y; z = p.z; return *this;

3 #include point.h int main ( ) { Point a (3,2,1), b(13,14,15), c; a.displaypoint ( ); b.pisplaypoint ( ); c = a + b; c.displaypoint ( ); c = a + b + c; c.displaypoint ( ); c = b = a; c.displaypoint ( ); b.displaypoint ( ); Operator Overloading de kisitlamalar Operator overloading le operator lere built-in type lerdeki davranislaridan farkli bir davranis kazandirilamaz Operator e en az bir tane user-defined type veya class i argument olarak almali Operator overloading implicitly olmaz # i overload etmek # = I de overload etmek anlamina gelmez == i overload etmek!= de overload etmek anlamina gelmez Hint: ilgili bir kac operator u overload etmek istersek, her birini ayri ayri overload etmek gerekir (explicitly) Overloading parameter sayisini degistiremez return 0; 12/10/2004 Nesneye Yonelik Programlama /10/2004 Nesneye Yonelik Programlama /10/2004 Nesneye Yonelik Programlama /10/2004 Nesneye Yonelik Programlama 8.12

4 12/10/2004 Nesneye Yonelik Programlama /10/2004 Nesneye Yonelik Programlama 8.14 C++ << ve >> ye nasil davranir? C++ compiler cout << phone ile karsilastiginda, bunu function cagrimi syntax ina operator<< (ostream &, const PhoneNumber &) donusturur. Sonuc sonraki output argument leri kabul eden ostream dir ( << left associative) C++ compiler cin >>phone ile karsilastiginda, bunu function cagrimi operator>>(istream &, PhoneNumber &) synax ina donusturur. Sonuc daha sonraki input argument lerini kabul eden istream dir ( >> left associative ) 12/10/2004 Nesneye Yonelik Programlama /10/2004 Nesneye Yonelik Programlama 8.16

5 Complex class i icin extraction operator (>>) unun overload oldugunu varsayalim. istream &operator>> (istream &input, Complex &cnum) { input >> cnum.real >> cnum.imag; return input; Overloaded operator su sekilde kullanilabilir Complex c_obj; cin >> c_obj; Ikinci statement cin >> c_obj; asagidaki statement a esit operator>> (cin, c_obj ); ve evaluate edildiginde ise cin >> c_obj.real >> c_obj.imag; e esittir 12/10/2004 Nesneye Yonelik Programlama 8.17 Her iki parameter da reference ile gecirilir System stream lar hakkinda bir takim bilgileri update ettiginden dolayi, stream object leri daima reference ile function a gecirilir Ikinci objec (Complex object) in data member lari update edildiginden function a reference ile gecirilir Stream reference olarak geri dondurulur. Boylece input (output) u cascade edebiliriz Complex c1_obj, c2_obj; cin >> c1_obj >> c2_obj; 12/10/2004 Nesneye Yonelik Programlama 8.18 Single call (tekli cagrim) olarak kullanildiginda: cin >> c_obj; Dondurulen deger kullanilmaz. Ikinci argument c_obj birinci argument e gore degistirilir. Cascade (chain) olarak cagrim yapildiginda: cin >> c1_obj >> c2_obj; Ikinci argument c1_obj birinci argument cin e gore degistirilir ve dondurulen deger ikinci function cagrimi icin ilk argument gorevini gorur operator >> (input, c2_obj ); Buradaki input c1_obj nin degerini iceren istream object idir 12/10/2004 Nesneye Yonelik Programlama 8.19 Unary Operator Overloading Unary operatorlerin overloading in iki yolu Argumentsiz non-static member fonksiyonu kullanarak (object argument olarak davranir) Ornek: class String { public: bool operator!() const;. ; Bir argumentli non-member function kullanarak (argument object veya object e reference olmali) Ornek: class String { friend bool operator! (const String &). 12/10/2004 ; Nesneye Yonelik Programlama 8.20

6 Binary Operator Overloading Binary operatorlerin overloading in iki yontemi Bir argument li non-static member function kullanarak (object ikinci argument olarak davranir) class String { public: const String &operator+= ( const String & );. ; Iki argumentli bir non-member function kullanarak (argumentlerden birtanesi object veya object e ref olmali) class String { friend const String &operator+= (String &, const String &). ; 12/10/2004 Nesneye Yonelik Programlama 8.21 Copy Constructors & Assignment Operators Default olarak, bir object assign edildiginde veya object in kopyasi gerektiginde, memberwise copy kullanilarak kopyalama islemi gerceklestirilir Eger object ler dynamic olarak allocate edilen bellek alanlarina sahipse problemlere yol acar Bir kopyayi yok etmek allocate edilen memory nin delete edilmesi anlamina gelir ve diger object tarafindan point edilen memory alaninin da yok edilmesi anlamina gelir Cozum: dynamic olarak allocate edilen object lerinin kopyasini olusturmak icin bir copy constructor ve bir overloaded assignment operator tanimla 12/10/2004 Nesneye Yonelik Programlama /10/2004 Nesneye Yonelik Programlama /10/2004 Nesneye Yonelik Programlama 8.24

7 Copy Constructors Class declaration da, sunu ilave et <class_name> (const <class_name> &) Yeni member fonksiyonun definitioni (1) dynamic olarak create edilen butun subobject ler icin gerekli memory allocate edilmeli (2) verilen object in sub-objectlerinin icerigi copy object e verilmeli Copy Constructor class icin copy constructor tanimlandiginda, copy constructor automatic olarak asagidaki durumlarda cagrilir Bir object fonksiyona call-by-value ile gecirildiginde Bir fonksiyondan bir object donduruldugunde Var olan bir object in kopyasi olarak yeni bir object initialize edildiginde 12/10/2004 Nesneye Yonelik Programlama /10/2004 Nesneye Yonelik Programlama 8.26 Assignment Operator Overloading class declaration da sunu ilave et const <class> &operator= (const <class> &); Diger binary overator lerin overloading inde oldugu gibi, compiler su kod ornegini object = object2; asagidaki function call ile yer degistirir object1.operator= (object2); Assignment operator function taniminda Self-assignment a izin verilmemeli Cascaded assignment lara izin vermek icin object e bir pointer geri dondur ( return *this) (ornek: object1 = object2 = object3; ) 12/10/2004 Nesneye Yonelik Programlama 8.27 built-in type lar arasinda donusum C++ compiler operator ler farkli type sahip argumentlere uygulandiginda guvenli type cevrimleri icin automatic olarak code yerlestirir (promotion veya implicit conversion) Ornek: int + double double sonuc uretir Bazen programci explicit (acik) type conversion a ihtiyac duyar Ornek: avg = static_cast<float>(sum) / num; Syntax: static_cast < <typename> > ( <argument>) 12/10/2004 Nesneye Yonelik Programlama 8.28

8 user-defined type lar arasinda donusum Cast Operator Functions Bazen user-defined type ler arasinda cevrime ihtiyac duyabiliriz. Bu is icin programci conversion function(s) lari tanimlamali Conversion constructors: Tek argument alan ve argument tipini (built-in type veya user-defined type) ini object type ine ceviren constructor Conversion ( cast ) operators: Non-static member function kullanarak bir class a ait object i Cast operator decleration syntax i: <old_class>::operator<new_class> const; Semantics: Input parameter i <old_class> type inden <new_class> in bir object ine donusturur return type gerekmez cast operator soyle cagrilir (newclass ) objectname ; baska bir class in object ine cevir 12/10/2004 buit-in type object Nesneye e cevir Yonelik Programlama /10/2004 Nesneye Yonelik Programlama 8.30 overloaded cast operator functions Iki veya daha fazla cast operator ler overload edilmek suretiyle class in object I iki veya daha fazla user-defined (buil-in defined) class larin object lerine donusturulur class A { public: operator int( ) const; operator double ( ) const; operator B ( ) const; private: 12/10/2004 Nesneye Yonelik Programlama 8.31 ; cast operator lerini kullanarak implicit conversions Bir dizi cast function lari tanimlandigi zaman compiler bunlari kullanarak implicit type conversion yapar Ornek: kullanici tarafindan bir cast operator u tanjimlandigini ve bunun class A nin objec lerini char * ya cevirdigini varsayalim compiler operator char * automatic olarak cagirmak suretiyle asagidaki code un dogru sonuc uretmesini saglayacak cout << objectname; // objectname class A nin object i 12/10/2004 Nesneye Yonelik Programlama 8.32

9 Overloading ++ and -- Prefix operators (preincrement ve predecrement) diger prefix unary operator ler gibi implement overload edilebilirler Postfix operators (postincrement ve postdecrement) operatorlere 0 degerli bir dummy input parameter verilmek suretiyle prefix versiyonlarindan ayirt edilirler 12/10/2004 Nesneye Yonelik Programlama 8.33 overloading preincrement operator Method 1: member function kullanarak s nin class A nin objetct i oldugunu varsayalim Compiler ++s yi gordugunde s.operator++( ) yi uretir Dolayisiyle class A, A &operator++( ) member function a sahip olmali Function definition A &A::operator++ ( ) Method 2: non-member friend function kullanarak friend A &operator++ (A &) // decleration A &operator++ (A &) // definition 12/10/2004 Nesneye Yonelik Programlama 8.34 overloading postincrement operator Method 1: member function kullanarak s nin class A nin objetct i oldugunu varsayalim Compiler s++ yi gordugunde s.operator++(0 ) yi uretir Dolayisiyle class A, A &operator++(int ) member function a sahip olmali Function definition A &A::operator++ (int ) Method 2: non-member friend function kullanarak friend A &operator++ (A &, int) // decleration A &operator++ (A &, int) // definition 12/10/2004 Nesneye Yonelik Programlama 8.35 #include <iostream.h> #include <stdlib.h> struct CELL{ int element; struct CELL *next; ; class List{ public: List( ); List(const List &); ~List( ); void Add_element(int); void Remove_element(int); void print( ); const List& operator=(const List &); const List& operator++(); const List operator++(int); void sort( ); private: struct CELL *list_header; struct CELL* create_element(int); struct CELL* insert_sorted_list(struct CELL*,struct CELL*); ; 12/10/2004 Nesneye Yonelik Programlama 8.36

10 struct CELL* List::create_element(int i) { struct CELL *ptr; ptr = (struct CELL *) malloc(sizeof(struct CELL)); ptr->element = i; return ptr; List::List( ) { cout<<"birinci List constructor cagrildi\n"; list_header = 0; List::List(const List &list) { struct CELL *temp1, *temp2; cout<<"ikinci List constructor cagrildi\n"; list_header = 0; if(list.list_header == 0) return; temp2=list.list_header; temp1 = list_header = create_element(temp2->element); temp2 = temp2->next; while(temp2) { temp1->next = create_element(temp2->element); temp2 = temp2->next; temp1 = temp1->next; temp1->next = 0; List::~List( ) { struct CELL *temp; cout << List destructor cagrildi\n"; temp= list_header; while(temp) { list_header = list_header->next; delete temp; temp=list_header; 12/10/2004 Nesneye Yonelik Programlama /10/2004 Nesneye Yonelik Programlama 8.38 const List& List::operator=(const List & input_list) { struct CELL *header1 = list_header; struct CELL *header2 = input_list.list_header, *temp = 0; if(header2==0) list_header = 0; while (header1 && header2) { temp = header1; header1->element = header2->element; header1 = header1->next; header2 = header2->next; // while if(header2 == 0) { if (temp) temp->next = 0; temp = header1; while (temp) { header1 = header1->next; delete temp; temp = header1; // while // if (header == 0) else { if(header2 &&!list_header) { list_header = temp = create_element(header2->element); header2=header2->next; while(header2) { temp->next = create_element(header2->element); temp = temp->next; header2 = header2->next; // while if(temp) temp->next = 0; // else return *this; 12/10/2004 Nesneye Yonelik Programlama 8.39 const List& List::operator ++() { struct CELL *temp = list_header; while(temp) { temp->element++; temp = temp->next; return *this; const List List::operator ++(int) { struct CELL *temp_header = list_header; List temp = *this; while(temp_header) { temp_header->element++; temp_header = temp_header->next; return temp; 12/10/2004 Nesneye Yonelik Programlama 8.40

11 void List::Add_element(int i) { struct CELL *new_element_ptr = create_element(i); new_element_ptr->next = list_header; list_header = new_element_ptr; void List::Remove_element(int i) { struct CELL *temp1,*temp2; temp1=temp2=list_header; while(temp2) { if(temp2->element == i) { if(temp1==temp2) list_header = temp2->next; else temp1->next=temp2->next; void List::print( ) { struct CELL *temp_ptr = list_header; cout<<endl; while(temp_ptr) { cout << temp_ptr->element << ; temp_ptr=temp_ptr->next; cout <<endl; free(temp2); break; temp1=temp2; temp2=temp2->next; 12/10/2004 Nesneye Yonelik Programlama /10/2004 Nesneye Yonelik Programlama 8.42 struct CELL* List::insert_sorted_list(struct CELL* header, struct CELL* cell) { if(!header) { cell->next = 0; return cell; else if(cell->element <= header->element) { cell->next = header; return cell; else { header->next = insert_sorted_list(header->next,cell); return header; void List::sort( ) { struct CELL *temp1,*temp2; temp1 = list_header; list_header = 0; while (temp1) { temp2=temp1->next; list_header = insert_sorted_list(list_header,temp1); temp1 = temp2; 12/10/2004 Nesneye Yonelik Programlama 8.43 class Stack{ public: Stack( ); // default constructor Stack(Stack &); // copy constructor ~Stack( ); // destructor void push(int); bool pop(int &); void print( ); operator List( ) const; // overloading cost operator operator List*( ) const; // overloading cost operator private: struct CELL *stack_ptr; ; 12/10/2004 Nesneye Yonelik Programlama 8.44

12 Stack::Stack( ) { cout << "birinci Stack constructor cagrildi\n"; stack_ptr = 0; Stack::Stack(Stack & stack) { CELL *temp = stack.stack_ptr; CELL *cell; cout << ikinci Stack constructor cagrildi\n"; stack_ptr = 0; if (!temp) return; stack_ptr = cell = (struct CELL *) malloc(sizeof(struct CELL)); cell->element = temp->element; temp = temp->next; while(temp) { cell->next = (struct CELL *) malloc(sizeof(struct CELL)); cell->next->element = temp->element; cell = cell->next; temp = temp->next; cell->next = 0; Stack::~Stack( ) { CELL *temp; cout <<"Stack destructor cagrildi\n"; while(stack_ptr) { temp = stack_ptr->next; free(stack_ptr); stack_ptr = temp; 12/10/2004 Nesneye Yonelik Programlama 8.45 void Stack::push(int element) { CELL *cell = (struct CELL *) malloc(sizeof(struct CELL)); cell->element = element; cell->next = stack_ptr; stack_ptr = cell; bool Stack::pop(int &element) { if(!stack_ptr) return false; else { CELL *cell = stack_ptr->next; element = stack_ptr->element; free(stack_ptr); stack_ptr = cell; return true; void Stack::print( ) { CELL *cell = stack_ptr; cout << endl; while(cell) { cout << cell->element <<" "; cell = cell->next; cout << endl; 12/10/2004 Nesneye Yonelik Programlama 8.46 Stack::operator List( ) const { List list; CELL *cell = stack_ptr; while(cell) { list.add_element(cell->element); cell = cell->next; return list; Stack::operator List*( ) const { List *list = new List; CELL *cell = stack_ptr; while(cell) { list->add_element(cell->element); cell = cell->next; return list; 12/10/2004 Nesneye Yonelik Programlama 8.47 int main( ) { class List list1; // 1 list1.add_element(10); // 2 list1.add_element(20); // 3 list1.add_element(40); list1.print(); // 4 class List list2; // 5 list2 = list1++; // 6 list1.print(); // 7 list2.print(); // 8 class Stack stack1; // 9 stack1.push(3000); stack1.push(5000); // 10 stack1.push(1000); stack1.push(4000); // 11 stack1.print( ); // 12 class Stack stack2 = stack1; // 13 int element; // 14 if (stack2.pop(element)) // 15 cout << element <<endl; // 16 stack2.print( ); // 17 list1 = (List) stack2; // 18 cout <<"------\n"; // 19 list1.print( ); // 20 class List *list_ptr; // 21 list_ptr = (List*)stack1; // 22 list_ptr->print( ); // 23 delete list_ptr; // 24 return 12/10/2004 0; Nesneye // Yonelik 25 Programlama 8.48