```/*
*
*  This file is the solution to an exercise problem posed during
*  one of the UW CSE 333 lectures (333exercises).
*
*  333exercises is free software: you can redistribute it and/or modify
*  the Free Software Foundation, either version 3 of the License, or
*  (at your option) any later version.
*
*  333exercises is distributed in the hope that it will be useful,
*  but WITHOUT ANY WARRANTY; without even the implied warranty of
*  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*  GNU General Public License for more details.
*
*  You should have received a copy of the GNU General Public License
*  along with 333exercises.  If not, see <http://www.gnu.org/licenses/>.
*/

// lec 10 exercise 1

#ifndef _LEC10_EX1_THREEDPOINT_H_
#define _LEC10_EX1_THREEDPOINT_H_

#include <iostream>

using namespace std;

// A "ThreeDPoint" is a class representing a three-dimensional point.
// Internally, a ThreeDPoint is represented with doubles for the x, y,
// and z axis values.
class ThreeDPoint {
public:

// Constructors; we use initialization lists to initialize.
ThreeDPoint() : x_(0), y_(0), z_(0) { }
ThreeDPoint(const double x, const double y, const double z)
: x_(x), y_(y), z_(z) { }

// Copy constructor.
ThreeDPoint(const ThreeDPoint &pt);

// Accessors (inlined).
double get_x() const { return x_; };
double get_y() const { return y_; };
double get_z() const { return z_; };

// Inner product.
double InnerProduct(const ThreeDPoint &pt) const;

ThreeDPoint operator+(const ThreeDPoint &pt) const;
ThreeDPoint operator-(const ThreeDPoint &pt) const;

ThreeDPoint &operator+=(const ThreeDPoint &pt);
ThreeDPoint &operator-=(const ThreeDPoint &pt);

// Assignment operator.
ThreeDPoint &operator=(const ThreeDPoint &pt);

// Override "<<" for std::ostream.
friend ostream &operator<<(ostream &out, const ThreeDPoint &pt);

private:
double x_, y_, z_;
};

#endif  // _LEC10_EX1_THREEDPOINT_H_
```