//circle.cpp
#include iostream.h>
#include conio.h>
#include graphics.h>
//两个<>在论坛上看不到,我少写了一个<

enum BOOLEAN
{
FALSE,
TURE
};

//location.cpp
class LOCATION
{
public:
LOCATION(int x,int y)
{ x_pos=x;
y_pos=y;
return;
}

~LOCATION()
{
return;
}

int get_x()
{
return(x_pos);
}

int get_y()
{
return(y_pos);
}

protected:
int x_pos;
int y_pos;
};
//point.cpp
class POINT:public LOCATION
{
public:
POINT(int x,int y):LOCATION(x,y)
{
visable=FALSE;
return;
}

~POINT()
{
return;
}

BOOLEAN is_visable()
{
return(visable);
}

void show()
{
if(!is_visable())
{
visable=TURE;
putpixel(x_pos,y_pos,getcolor()); //draw a circle
}
return;
}

void hide()
{ if(is_visable())
{
visable=FALSE;
putpixel(x_pos,y_pos,getbkcolor());
//draw a circle with backcolor
}
return;
}

void move_to(int x,int y)
{
hide();
x_pos=x;
y_pos=y;
show();
return;
}

protected:
BOOLEAN visable;
};

//circle.cpp
class CIRCLE:public POINT
{
CIRCLE(int x,int y,int r):POINT(x,y)
{
radius=r;
return;
}

~CIRCLE()
{
return;
}

void show()
{
if(!is_visable())
{
visable=TURE;
circle(x_pos,y_pos,radius);//draw a circle
}
return;
}

void hide()
{
if(is_visable())
{
visable=FALSE;
temp_color=getcolor(); //save current color
setcolor(getbkcolor());
circle(x_pos,y_pos,radius);
setcolor(temp_color);
}
return;
}
void move_to(int x,int y)
{
hide();
x_pos=x;
y_pos=y;
show();
return;
}

void expand(int delta)
{
hide();
radius=radius+delta;
if(radius<0) radius=0;
show();
return;
}

void contract(int delta)
{ expand(-delta);
return;
}
protected:
int radius;
int temp_color;
};

int main()
{
int graphdriver=DETECT, graphmode;//define graph valiable
CIRCLE circle(100,200,50);
initgraph(&graphdriver,&graphmode," ");//init graph model

circle.show();
getch();
circle.move_to(200,250);
getch();
circle.expand(50);
getch();
circle.contract(65);
getch();
closegraph(); //close graph model
return 0;

}