Help with inheritance in c++

[jongiambi]

Hi so I have a practice lab I am working on where I am asked to fill in the code. The program is supposed to take in two 3D points (x,y,z) and compute the distance between them.

I have almosty all of the program finished im just stuck on how to call the inherited functions in main(). How do I pass my points (a,b,c) and (x,y,z) into the getDistance function? Would something like this work?:

cout << Obj3.getDistance(Obj2);

Here is my code:

// File name: ~ftp/pub/class/170/ftp/cpp/Inheritance/Exercise.cpp
// Purpose:   Exercise for inheritance lab

#include <iostream>
#include <math.h> // for sqrt()
using namespace std;

class twoD
{
protected:
    double x, y; // x and y  coordinates
public:
    // inline implementation of constructor
    twoD(){x = y = 0.0;} // default constructor
    twoD(double i, double j):x(i), y(j){}

    // inline implementation of member functions
    void setX(double NewX){x = NewX;}
    void setY(double NewY){y = NewY;}
    double getX() const {return x;}
    double getY() const {return y;}
    // get distance of 2D points
    double getDistance (twoD point) const;
};

// calculate the distance  of two 2D points
double twoD::getDistance(twoD point) const
{
    double point1[2];
    double point2[2];
    double dx, dy;
    double distance;

    point1[0] = x;
    point1[1] = y;

    point2[0] = point.getX();
    point2[1] = point.getY();

    dx = point2[0] - point1[0];
    dy = point2[1] - point1[1];

    distance = sqrt(dx * dx + dy * dy);
    return distance;
}

class threeD:public twoD
{
private:
    double z;
public:

    // --->ADD CODE HERE<---:
    // Create a default inline constructor that reuses the constructor of
    // the twoD class.
    // YOUR CODE GOES HERE
    threeD(double i, double j):twoD(i,j){z = 0.0;}


    // --->ADD CODE HERE<---:
    // Create an inline constructor that initializes the 3D point
    // and reuses the twoD class.
    // YOUR CODE GOES HERE
    threeD(double i, double j, double k):twoD(i,j){z = k;}


    void setZ(double NewZ){z = NewZ;}
    double getZ() {return z;}

    // get distance for two 3D points
    double getDistance(threeD point) const;
};

// --->ADD CODE HERE<---:
// Overload the definition of getDistance() of twoD class so that it
// can calculate the distance between two 3D points
// YOUR CODE GOES HERE:
double threeD::getDistance(threeD point) const
{
    double point1[3];
    double point2[3];
    double dx, dy, dz;
    double distance;

    point1[0] = x;
    point1[1] = y;
    point1[2] = z;

    point2[0] = point.getX();
    point2[1] = point.getY();
    point2[2] = point.getZ();

    dx = point2[0] - point1[0];
    dy = point2[1] - point1[1];
    dz = point2[2] - point1[2];

    distance = sqrt(dx * dx + dy * dy + dz * dz);
    return distance;
}

// --->ADD CODE HERE<---:
// Implement a main() function.
// You should ask the user for the xyz coordinates of two 3D points,
// and then calculate and print out the distance between these two points.
int main()
{
    // YOUR CODE GOES HERE
    double a,b,c;
    double x,y,z;

    cout << "Enter the x,y,z coordinates of point 1: " << endl;
    cin >> a >> b >> c;
    cout << "Point one is: (" << a << ", " << b << ", " << c << ")" << endl;
    cout << endl;

    cout << "Enter the x,y,z coordinates of point 2: " << endl;
    cin >> x >> y >> z;
    cout << "Point two is: (" << x << ", " << y << ", " << z << ")" << endl;
    cout << endl;


    threeD Obj3(x, y, z);
    threeD Obj2(a, b, c); 



    return 0; 
}

[jongiambi]

Oops! Just realized this line

cout << Obj3.getDistance(Obj2);

is correct. Guess I solved my own problem.

[rubberman]

Good for you! Another approach would be a function (not class member method) double distanceBetween(const threeD& ptA, const threeD& ptB), which could be used anywhere.It may be more reasonable for general algorithms as well. In any case, this is just a suggestion. Your approach is perfectly reasonable.