Data Structures Using C++1 Chapter 3 Pointers Dr. Liu

Data Structures Using C++2 Chapter Objectives Learn about the pointer data type and pointer variables Explore how to declare and manipulate the pointer variables Learn about the address of operator and dereferencing operator Discover dynamic variables Examine how to use the new and delete operators to manipulate dynamic variables

Data Structures Using C++3 Chapter Objectives Learn about pointer arithmetic Discover dynamic arrays Become aware of the shallow and deep copies of data Discover the peculiarities of classes with pointer data members Explore how dynamic arrays are used to process lists

Data Structures Using C++4 What are pointers ? Variables that store memory address How to De-reference pointers How to do Pointer assignment How to use address-of operator

Data Structures Using C++5 What are pointers ? abcpabcp Address int *p; int a = 5; p = &a; what is *p now ?; *p = *p + b; int c = *p;

Data Structures Using C++6 Pointer Data Types and Pointer Variables Pointer variable: variable whose content is a memory address Syntax to declare pointer variable: dataType *identifier; e.g. int *p; Address of operator: Ampersand, &, e.g. &a Dereferencing operator: Asterisk, *

Data Structures Using C++7 Pointers Statements: int *p; int num;

Data Structures Using C++8 Pointers

Data Structures Using C++9 Pointers

Data Structures Using C++10 Pointers

Data Structures Using C++11 Pointers Summary of preceding diagrams –&p, p, and *p all have different meanings –&p means the address of p –p means the content of p –*p means the content pointed to by p, that is pointed to by the content of memory location

Data Structures Using C++12 Pointers

Data Structures Using C++13 Pointers x = 50; p = &x;

Data Structures Using C++14 Pointers *p = 38;

Data Structures Using C++15 Example 1 // This program passes the address of a variable to a // function, which triples the value pointed to. Pointer example demo 1 void triple_it(int *n);

Data Structures Using C++16 Example 2 // This program sorts an array from hightest member // down to lowest, in that order. Pointer example demo 2. void swap(int *p1, int *p2)

Data Structures Using C++17 Example 3 void zero_out_array(int *arr, int n); void zero_out_array(int *p, int n) { while (n-- > 0) { // Do n times: *p = 0; // Assign 0 to element // pointed to by p. p++; // Point to next element. }

Data Structures Using C++18 Classes, structs, and Pointer Variables The syntax for accessing a class (struct) member using the operator -> is pointerVariableName->classMemberName Therefore, the statement (*studentPtr).gpa = 3.9; is equivalent to the statement studentPtr->gpa = 3.9;

Data Structures Using C++19 Classes, structs, and Pointer Variables

Data Structures Using C++20 Classes, structs, and Pointer Variables

Data Structures Using C++21 Syntax to use operator new new dataType; //to allocate a single variable new dataType[intExp]; //to allocate an array of variables

Data Structures Using C++22 Syntax to use operator delete delete pointer; //to destroy a single dynamic variable delete [] pointer; //to destroy a dynamically created array

Data Structures Using C++23 Operations on pointer variables Assignment operations Relational operations Limited arithmetic operations

Data Structures Using C++24 Functions and Pointers void example(int* &p, double *q) {. }

Data Structures Using C++25 Functions and Pointers void example(int* &p, double *q) {. }

Data Structures Using C++26 Pointers and Function Return Pointers int* testExp(...) {. } is a pointer of the type int.

Data Structures Using C++27 #include #define PRINTEM printf("%3d%5d%5d%5d%5d%5d\n", line++, num, x[0],x[1],x[2], ptr-x) int main() { static int x[] = {5,10,15}, lim =99; int *ptr = x, num = 0; int line = 0; printf("LINE num x[0] x[1] x[2] ptr-x \n"); PRINTEM; printf("\n\n"); num = *ptr; PRINTEM; num = *++ptr; PRINTEM; num = *ptr++; PRINTEM; num = ++*ptr; PRINTEM; num = (*ptr)++; PRINTEM; num = ++(*ptr); PRINTEM; num = *ptr + 1; PRINTEM; num = *(ptr + 1); PRINTEM; return 0; }

Data Structures Using C++28 Shallow Versus Deep Copy and Pointers

Data Structures Using C++29 Shallow Versus Deep Copy and Pointers

Data Structures Using C++30 Shallow Versus Deep Copy and Pointers second = new int[10]; for(int j = 0; j < 10; j++) second[j] = first[j];

Data Structures Using C++31 Classes and Pointers: Some Peculiarities class pointerDataClass { public:... private: int x; int lenP; int *p; }; pointerDataClass objectOne; pointerDataClass objectTwo;

Data Structures Using C++32 Classes and Pointers: Some Peculiarities

Data Structures Using C++33 Destructor

Data Structures Using C++34 Destructor pointerDataClass::~pointerDataClass() { delete [ ] p; } class pointerDataClass { public: ~pointerDataClass();... private: int x; int lenP; int *p; };

Data Structures Using C++35 Assignment Operator

Data Structures Using C++36 Assignment Operator

Data Structures Using C++37 Assignment Operator

Data Structures Using C++38 Overloading the Assignment Operator Function Prototype (to be included in the definition of the class): const className& operator=(const className&); Function Definition: const className& className::operator=(const className& rightObject) { //local declaration, if any if(this != &rightObject) //avoid self-assignment { //algorithm to copy rightObject into this object } //return the object assigned return *this; }

Data Structures Using C++39 Overloading the Assignment Operator Definition of function operator=: –Only one formal parameter –Formal parameter generally const reference to particular class –Return type of function is reference to particular class

Data Structures Using C++40 Copy Constructor

Data Structures Using C++41 Copy Constructor

Data Structures Using C++42 Copy Constructor

Data Structures Using C++43 Copy Constructor If a class has pointer data members: –During object declaration, the initialization of one object using the value of another object would lead to a shallow copying of the data if the default memberwise copying of data is allowed –If, as a parameter, an object is passed by value and the default member-wise copying of data is allowed, it would lead to a shallow copying of the data

Data Structures Using C++44 Copy Constructor The copy constructor automatically executes in the following situations –When an object is declared and initialized by using the value of another object –When, as a parameter, an object is passed by value –When the return value of a function is an object

Data Structures Using C++45 Copy Constructor

Data Structures Using C++46 Copy Constructor General syntax to include the copy constructor in the definition of a class: className(const className& otherObject);

Data Structures Using C++47 Classes with Pointer Data Members Include destructor in the class Overload assignment operator for class Include copy constructor

Data Structures Using C++48 Overloading Array Index (Subscript) Operator ([ ]) Syntax to declare the operator function operator [ ] as a member of a class for nonconstant arrays: Type& operator[](int index); Syntax to declare the operator function operator [ ] as a member of a class for constant arrays: const Type& operator[](int index) const;

Data Structures Using C++49 Chapter Summary Pointer data types and variables Dynamic variables Pointer arithmetic Dynamic arrays Shallow and deep copying Peculiarities of classes with pointer data members