Advanced Programming

Constants(상수), Declarations(선언), and Definitions(정의) Advanced Programming Derived Data Types

Derived Data Types • Class • Structure (구조) • Union (집합) • Enumeration (열거하다) • Array (정렬시키다) • Function (함수) • Pointer • Reference (인용,참조)

Class • Collection of Homogeneous (동차의)Objects • Information Hiding -- Data Members and Member Functions #include <iostream>using std::cout; using std::endl;class student{ private: char* name; public: void add_name(char *ip1) { name = new char[10]; strcpy(name, ip1);} char* get_name() {return name;} }; main() { student s1; //object or instance s1.add_name("John"); cout << "Name: " << s1.get_name() << endl; }

Structure • Collection of Objects a Having Meaningful Representation(표현) • A Class with ALL PUBLIC MEMBERS struct date{ int day; char *month; int year; }; #include <iostream>using std::cout; using std::endl;main() { struct date today; //object today.day = 15; today.month = "May"; today.year = 1995; cout << "Date is: " << today.month << " " << today.day << " " << today.year << endl; } (There is a strong correlation(상호관계) between classes and structures.)

Union(집합) • Objects to Occupy(차지하다) Same Area of Storage(기억장치) • Different Types at Different Times struct circle{ int radius; }; struct triangle{ int side1; int side2; int angle; }; struct rectangle{ int side1; int side2; }; union shape{ struct circle s1; struct triangle s2; struct rectangle s3; }; Using the correct name is critical(중요하다). Sometimes you need to add a tag field to help keep track. It is important that the tag field be in the same location in every variant(다른).

Enumeration(열거하다) • Assigns(할당하다) Numerical(수치의) Values to List of Identifiers (식별자) enum binary {zero, one}; enum number {one = 1, two, three}; enum boolean {False, True}; main() { boolean x = False; if (x) {cout << "True!" << endl;} else {cout << "False!" << endl;} }

Reference(인용,참조) An alias(별명) of an object Must be initialized(초기화 하다) when defined(정의하다) No operator(조작자) acts on reference Value of a reference cannot be changed after initialization (초기화) – it always refers to the object it was initialized to. (Compile time, not run time.) main(){ int i = 10, &j = i; j = 5; cout << i; } This is the first new C++ capability(기능). You can’t do this in C.

Object Storage(기억장치) Persistent(완고한,잠복기간이긴) – alive after the program termination(종료) Non-persistent – alive during the program execution(실행) C++ allows only non-persistent objects Automatic variables(변수) are allocated(배정하다) and destroyed(파괴하다) automatically Dynamic allocation(배정) is achieved(~이루다) by using new and delete operators(연산자).

Constant(상수) Declarations(선언) • const Keyword Makes the Object Constant • const as a Prefix in a Pointer Declaration MAKES THE OBJECT POINTED TO BE A CONSTANT AND NOT THE POINTER! • Use of *const Makes the POINTER to be a CONSTANT

Constant Declarations(선언) const int x = 10; /* x is a Constant Object */ const int y[] = {1, 2, 3, 4}; // y is a Array(정렬) of Constant Objects const char *ptr = "csci220"; /* ptr: Pointer to a CONST OBJECT ptr[0] = 'R'; //ERROR!!! ptr = "Class_Notes"; /* ptr CAN POINT TO ANOTHER CONSTANT OBJECT! */ char *const cptr = "C++"; // cptr is a CONSTANT POINTER cptr[0] = 'c'; //LEGAL cptr = "Assignment"; //ERROR!! cptr CANNOT POINT TO // ANOTHER CONSTANT OBJECT! const char* const dptr = "Simple_Language"; /* dptr is a CONSTANT POINTER pointing to a CONSTANT OBJECT */ dptr[0] = 's'; //ERROR!! dptr = "Difficult_Language"; //ERROR!!

Declaration(선언) • Describes(묘사하다) the form of an Object • DOES NOT Reserve Any Storage(기억장치) • Initialization(초기화하다) is NOT Allowed Definition(정의) • Creates an Instance(사례,실례) • Creates an Instance • Reserves a Storage • Initialization is Allowed • All Objects MUST BE DEFINED BEFORE THEIR USE

Declaration(선언) != Implementation • Function(기능) Without Body • Contains extern Specifier(상술하다) and NO Initializer(초기화) or Function Body • Static(정적) Member in the Class Declaration • Class Name Declaration • typedef Declaration

Examples /* Definitions */ int i, j; //storage is reserved int k = 10; //initialization /* Declarations */ int my_function(); //function extern int x; //external variable struct S; //structure typedef int INT; //typedef /* Implementation */ int my_function() { int i = 100; return(i); }

Incomplete(불완전한) Declarations • Dimension(차원,치수) is Not Specified(상술하다) • Class/Structure Body is Not Specified • Completed By Subsequent(차후의) Declaration struct S; //incomplete S *ps; //Acceptable S s1; //ERROR struct S { int x; char *ptr; }; // Complete Declaration S s2; //FINE int array[]; //incomplete int array[5]; //FINE

Typedef • Defines(정의를내리다) an Alias for Previously(본래의) Defined Data Type • Does NOT Create a New Type • Makes Programs Readable(읽힘성) typedef int INT; //INT => int INT x; //x is an integer variable INT y[10]; //Array typedef int *INT_PTR; //Pointer to int INT_PTR ptr; //ptr is a pointer to int /* Unnamed Class or Struct in a "typedef" gets the typedef as its name */ typedef struct { int p; char *q; } S; //struct is called S S my_struct; //instance of S

Interpretation(해석) of Declaration • Order of Evaluation(계산,평가) Depends Upon the Precedence(우선순위) and Associativity (연합) int (*fun[])(); /* Explanation 1. () Alter the Order of Evaluation 2. [] has Highest Precedence => fun is an array of 3. *fun[] => Pointers to 4. () => Functions Returning (required) 5. int => Integers ==> fun is an array of pointers to functions returning integers */

Scope(유효범위) Resolution Operator (::) • Can declare(밝히다) local and global(전역의) variable(변수) of same name. • In C, the local variable(변수) takes precedence(우선순위) over the global variable throughout(통하여) its scope. • In C++, the scope resolution operator(연산자) is used to access(접근) the variable of the same name in an outer(밖의) block. • Example int i; main() { int i; i = 35; ::i = 34; cout << "Local i = " << i << endl; cout << "Global i = " << ::i << endl; }

Acknowledgements(인지) • These slides were originally produced by Rajeev Raje, modified(변경) by Dale Roberts.

Advanced Programming