extern int x; // object declaration
std::size_t numDigits(int number); // function declaration
class Widget; // class declaration
template<typename T> // template declaration
class GraphNode; // (see Item 42 for info on
// the use of "typename")int x; // object definition
std::size_t numDigits(int number) // function definition.
{
// (This function returns
std::size_t digitsSoFar = 1; // the number of digits
// in its parameter.)
while ((number /= 10) != 0) ++digitsSoFar;
return digitsSoFar;
}
class Widget {
// class definition
public:
Widget();
~Widget();
...
};
template<typename T> // template definition
class GraphNode {
public:
GraphNode();
~GraphNode();
...
};class A {
public:
A(); // default constructor
};
class B {
public:
eXPlicit B(int x = 0, bool b = true); // default constructor; see below
}; // for info on "explicit"
class C {
public:
explicit C(int x); // not a default constructor
};void doSomething(B bObject); // a function taking an object of
// type B
B bObj1; // an object of type B
doSomething(bObj1); // fine, passes a B to doSomething
B bObj2(28); // fine, creates a B from the int 28
// (the bool defaults to true)
doSomething(28); // error! doSomething takes a B,
// not an int, and there is no
// implicit conversion from int to B
doSomething(B(28)); // fine, uses the B constructor to
// explicitly convert (i.e., cast) the
// int to a B for this call. (See
// Item 27 for info on casting.)class Widget {
public:
Widget(); // default constructor
Widget(const Widget& rhs); // copy constructor
Widget& operator=(const Widget& rhs); // copy assignment operator
...
};
Widget w1; // invoke default constructor
Widget w2(w1); // invoke copy constructor
w1 = w2; // invoke copy
// assignment operatorWidget w3 = w2; // invoke copy constructor!bool hasAcceptableQuality(Widget w);
...
Widget aWidget;
if (hasAcceptableQuality(aWidget)) ...
更多內(nèi)容請看C/C++技術(shù)專題專題，或 int *p = 0; // p is a null pointer
std::cout << *p; // dereferencing a null pointer
// yields undefined behavior
char name[] = "Darla"; // name is an array of size 6 (don’t
// forget the trailing null!)
char c = name[10]; // referring to an invalid array index
// yields undefined behaviora * boperator*(a,b)const Rational operator*(const Rational& lhs, const Rational& rhs);Widget *pw; // pw = ptr to Widget
class Airplane;
Airplane *pa; // pa = ptr to Airplane
class GameCharacter;
GameCharacter *pgc; // pgc = ptr to GameCharacter 更多內(nèi)容請看C/C++技術(shù)專題專題，或新聞熱點(diǎn)
疑難解答
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