, . , . , , . . , .
: , (, ). std::string (#include <string>), , . , ( , ):
struct Person /* "" */
{
std::string firstname, lastname; /* , */
};
, : , , , . (, , ), Person :
struct Employee: Person /* ""; "" */
{
std::string department; /* */
};
Employee department, firstname lastname, Person. , Employee:
Employee e;
e.firstname = "Ivan";
e.lastname = "Petrov";
e.department = "sales";
std::cout << e.firstname << ", " << e.lastname << ", " <<
e.department << "\n";
e Person , Employee. , ( Person), (base), (Employee) (derived). : , . :
class Person
{
public:
std::string firstname, lastname;
};
C++ , private. , Employee, (firstname lastname . :
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class Employee: public Person
{
public:
std::string department;
};
, public.
Person Employee : () public ( ). , . Person, firstname lastname :
class Person
{
std::string firstname, lastname; /* */
public:
Person(std::string f, std::string l): firstname(f),
lastname(l)
{ }
std::string getFirstname() { return firstname; }
std::string getLastname() { return lastname; }
};
, Person(std::string f, std::string l): firstname(f), lastname(l) { } . , firstname lastname. Person ( { }). , : Person(std::string f, std::string l) { firstname = f; lastname = l; } firstname lastname , . Person, :
Person p("Ivan", "Petrov");
std::cout << p.getFirstname() << ", " <<
p.getLastname() << "\n";
? , getFirstname() getLastname() Employee, . . public . , firstname lastname Employee, Employee : firstname(f) . , , , Person :
class Employee: public Person
{
std::string department;
public:
Employee(std::string f, std::string l, std::string d):
Person(f, l), department(d)
{ }
std::string getDepartment() { return department; }
};
:
Employee e("Ivan", "Petrov", "sales");
std::cout << e.getFirstname() << ", " <<
e.getLastname() << ", " <<
e.getDepartment() << "\n";
Person ( firstname lastname Ivan Petrov ), Employee. : , .
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11. . ?
, (, , ). , , ~. .
class Rational
{
...
public:
~Rational()
{
}
};
( Rational) . , , .
. , ( ) , . : , , , .
:
1) ;
2) ;
3) ( this).
static, . ++, friend, . , , , . , , . :
class X {
int a;
friend void friend_set(X*, int);
public void member_set(int);
};
void friend_set(X* p, int i) {p->a = i;};
void X::member_set(int i) {a = i};
void f {
X obj;
friend_set(&obj, 10);
obj.member_set(10);
};
, , . , , . , matrix vector . . , . :
class matrix; //
class vector {
float v[4];
//...
friend vector multiply(const matrix&, const vector&);
};
class matrix {
vector v[4];
//...
friend vector multiply(const matrix&, const vector&);
};
, :
vector multiply(const matrix& m, const vector& v) {
vector r;
for (int i = 0; i < 4; i++) { // r[i] = m[i] * v
r.v[i] = 0;
for (int j = 0; j < 4; j++) r.v[i] += m.v[i][j] * v.v[j];
};
return r;
}
, , . , , , , . . this .
:
class X {
//...
void f();
};
class Y {
//...
friend void X::f();
};
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Y, :
class Y {
//...
friend class X;
};
, friend, . :
static void f() { /*... */};
class X { friend g(); };// extern g()
class Y {
friend void f();// : f()
};
static g() { /*... */};// :
