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03_billiards.cpp
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03_billiards.cpp
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#include <iostream>
#include <cstdlib>
using namespace std;
class Ball;
class Table {
public:
Table(int w, int h);
bool contains_point(int x, int y);
void reflect(Ball* b);
private:
int width;
int height;
};
class Ball {
public:
Ball(int _x, int _y, int _vx, int _vy, Table* t);
void move(int dt);
int get_x() { return x; }
int get_y() { return y; }
int get_vx() { return vx; }
int get_vy() { return vy; }
void set_location(int _x, int _y);
void set_speed(int _vx, int _vy);
private:
int x;
int y;
int vx;
int vy;
Table* table;
};
Table::Table(int w, int h)
{
if (w <= 0 || h <= 0)
abort();
width = w;
height = h;
}
bool Table::contains_point(int x, int y) {
return x >= 0 && x < width && y >= 0 && y < height;
}
void Table::reflect(Ball* b) {
int x = b->get_x();
int y = b->get_y();
int vx = b->get_vx();
int vy = b->get_vy();
while (!contains_point(x, y)) {
if (x < 0) {
x = -x;
vx = -vx;
}
if (x >= width) {
x = 2 * width - x;
vx = -vx;
}
if (y < 0) {
y = -y;
vy = -vy;
}
if (y >= height) {
y = 2 * height - y;
vy = -vy;
}
}
b->set_location(x, y);
b->set_speed(vx, vy);
}
Ball::Ball(int _x, int _y, int _vx, int _vy, Table* t)
{
table = t;
set_location(_x, _y);
set_speed(_vx, _vy);
}
void Ball::set_location(int _x, int _y) {
if (!table->contains_point(_x, _y))
abort();
x = _x;
y = _y;
}
void Ball::set_speed(int _vx, int _vy) {
vx = _vx;
vy = _vy;
}
void Ball::move(int dt)
{
x += vx * dt;
y += vy * dt;
if (!table->contains_point(x, y))
table->reflect(this);
}
int main()
{
Table t(100, 50);
Ball b(10, 20, 25, 5, &t);
b.move(10);
}