#ifndef _cube_h_defined_
#define _cube_h_defined_

class cube {

  public:

    cube(int s) {

      // Create a cube centered at the origin and having sides of length s
      // units.

      side = s;
      center_x = center_y = center_z = 0;
      }


    void move(int x, int y, int z) {

      // Move a cube x units along the x axis, y units along the y axis and z
      // units along the z axis.  Because the cube is a rigid body, moving the
      // center is equivalent to moving the cube.

      center_x += x;
      center_y += y;
      center_z += z;
      }


    bool interferes_with(cube c) {

      // Return true if cube c interferes with this cube, false otherwise.

      const int s1 = side/2;
      const int s2 = c.side/2;

      // Two cubes overlap if and only if the projection of the two cubes
      // overlap on all three axes.

	 return 
	   overlap(center_x - s1, center_x + s1, c.center_x - s2, c.center_x + s2) &&
	   overlap(center_y - s1, center_y + s1, c.center_y - s2, c.center_y + s2) &&
	   overlap(center_z - s1, center_z + s1, c.center_z - s2, c.center_z + s2);
      }

  private:

    // The length of this cube's side.

       int side;

    // The coordinates of this cube's center point.

       int center_x, center_y, center_z;


    bool overlap(int left1, int right1, int left2, int right2) const {

      // Return true if and only if any part of the interval (left1, right1)
      // overlaps with any part of the interval (left2, right2).  This code
      // assumes that left1 <= right1 and left2 <= right2.

      return (left2 <= right1) && (left1 <= right2);
      }
  };

#endif