circle.cpp

经典的<<C how to program>一书第三版的例程。非常适合于C的初学者。

// Fig. 19.4: circle.cpp
// Member function definitions for class Circle
#include "circle.h"

// Constructor for Circle calls constructor for Point
// with a member initializer then initializes radius.
Circle::Circle( double r, int a, int b )
   : Point( a, b )       // call base-class constructor
{ setRadius( r ); }

// Set radius of Circle
void Circle::setRadius( double r ) 
   { radius = ( r >= 0 ? r : 0 ); }

// Get radius of Circle
double Circle::getRadius() const { return radius; }

// Calculate area of Circle
double Circle::area() const
   { return 3.14159 * radius * radius; }

// Output a Circle in the form:
// Center = [x, y]; Radius = #.##
ostream &operator<<( ostream &output, const Circle &c )
{
   output << "Center = " << static_cast< Point >( c ) 
          << "; Radius = " 
          << setiosflags( ios::fixed | ios::showpoint )
          << setprecision( 2 ) << c.radius;

   return output;   // enables cascaded calls
}



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