class to hold 2 double values representing the x and y coordinates

[nickyeng]

i have a question from my paper, which i dont have the correct answer, so here i asking anyone who can help, provide me the appropriate answer.
-----------------------------------
Write a class called Point that holds two double values representing the x and y coordinates of a point on graph. Provide the following:

1. A suitable default constructor that can also take one or both of the 2 values as arguments. Default values should be 0.

2. Member function get_x and get_y to get each of the values.

3. Memeber function set_x and set_y to set each of the values.

4. An overloaded output operator to output the Point in the format:
(1.2, 3.4)

5. A member function "length" to return the distance of the point from the origin, i.e.(0,0). The formula is the sqrt(x2 + y2). (2 is the supercase to x and y)
-----------------------------

Here is my code that i done so far, but i could finish the function length(), and i'm not sure everything i coded is correct. So please help me.....

class Point {
public:
        Point(double x = 0, double y = 0) : x(x), y(y) {}
 
        double get_x() {
                return x;
        }
        double get_y() {
                return y;
        }
        void set_x(double xx) {
                x = xx;
        }
        void set_y(double yy) {
               y = yy;
        }
        std::ostream& operator<< (std::ostream& os, const Point& p) {
                 os << p.x << ", " << p.y;
                 return os;
        }
        Point length( ) {
                 // do something here
                 return something;
        }
private:
        double x;
        double y;
};
 

[RedSon]

The instructor has provided you with the formula for calculating the distance. If you assume that you have valid input all you have to do is take the y coordinates of "this" point and another point and use the formula to return the result.

[RedSon]

class Point {
public:
        Point(double x = 0, double y = 0) : x(x), y(y) {}
 
        double get_x() {
                return x;
        }
        double get_y() {
                return y;
        }
        void set_x(double xx) {
                x = xx;
        }
        void set_y(double yy) {
               y = yy;
        }
        std::ostream& operator<< (std::ostream& os, const Point& p) {
                 os << p.x << ", " << p.y;
                 return os;
        }
        Point length( ) {
                 // do something here
                 return something;
        }
private:
        double x;
        double y;
};
 

I'll write the method signature for you:

Point length(Point anotherPoint) 
{
   //calculate using the formula
   return the_result;
}
 

[horace1]

if function "length" is to return the distance of the point from the origin, i.e.(0,0) it should return a double not a Point??, e.g.

       double length( ) {     // ** return double??
                 return sqrt( ????   );
}
 

also I think the operator<<

       friend std::ostream  &operator<<(std::ostream& os, const Point& p) {
 

should be a friend if declared within the class otherwise the compiler could think it is the left shift operator<<() function

[RedSon]

Oh yea horace is right, it should return double not Point. But the arguments passed to the length function should be the same.

That was one of my "senior" moments.

Thats what i get for copying and pasting code.

[nickyeng]

so it is like this:

double length() {
       return sqrt(x2 + y2);
}
 

?

how about other member function i done , were they correct according to the question?

[Ganon11]

so it is like this:

double length() {
       return sqrt(x2 + y2);
}
 

?

how about other member function i done , were they correct according to the question?

The formula for the distance function actually requires you to square x and y - this was the meaning of the 2s in the original writing, they just weren't superscripted. The formula should be:

return sqrt(x * x + y * y);

[nickyeng]

oh yeah.
thanks for reminding me, Ganon11.

[RedSon]

so it is like this:

double length() {
       return sqrt(x2 + y2);
}
 

?

how about other member function i done , were they correct according to the question?

Everything else looks to be kosher, but you should really run and test your app yourself.

[nickyeng]

Everything else looks to be kosher, but you should really run and test your app yourself.

its a paper question, not real app.
there is no point to compile it and give me no error. Cos i dont know what my teacher's code would be.

thanks for the help tho.

[nickyeng]

Here i have next question, related to question above i think.
----------------
Now write a class called Vector (no relationship with an STL vector) that comprises a Point and 2 strings begin the names of the graph axes. Do not use inheritance in this case. Provide the following:

1. A suitable default constructor with 2 additional argumnets for these names. Default them to "x" and "y" respectively.

2. Do not allow the names of the axes to be changed after a Vector thas been created.

3. An output operator overload to output the vector in the format:
1.2x + 3.4y

4. An operator to add together 2 Vectors returning a third Vector. Raise an exception if the 2 Vectors have different axis names.
----------------------------------------------------------

Now this time i stuck here with "...comprises a Point and ....". What does it means to you?

I know those question should be easy but sometimes it does confusing ppl with unclear definition or explanation.

any ideas?
(i think it should similar to the code i posted before.)

[RedSon]

Now this time i stuck here with "...comprises a Point and ....". What does it means to you?

I know those question should be easy but sometimes it does confusing ppl with unclear definition or explanation.

any ideas?
(i think it should similar to the code i posted before.)

Its talking about designing a class that has as its member data (comprises a...) Point and whatever else it says.

[nickyeng]

does my code correct as following:

class Vector {
public:
    Vector(string x = "x", string x = "y"): x(x), y(y) {}
 
    friend std::ostream& operator<< (std::ostream& os, const Vector& v) {
        os << v.x << "x + " << v.y << "y";
        return os;
    }
 
    inline Vector operator+ (const Vector& v1, const Vector& v2) {
        Vector v3 = v1;
        return v3 += v2;
    }
private:
    const string x;
    const string y;
};
 

i am not sure about question (2), is it member data like string x, string y, make them as const member so that it cannot be changed?

how about other member function i wrote above. Are they correct according to questions ?

[RedSon]

First you don't include a Point in your Vector and second, I don't think your + operation will do what you are expecting it to do. You will have to debug that operation *very* carefully.

Also, in the future feel free to start a new thread for any new questions. Bits are fully recyclable, environmentally friendly and cheap!

[nickyeng]

First you don't include a Point in your Vector and second, I don't think your + operation will do what you are expecting it to do. You will have to debug that operation *very* carefully.

Also, in the future feel free to start a new thread for any new questions. Bits are fully recyclable, environmentally friendly and cheap!

Redson,
i'm not completely new to here, so i know when to start a new thread for any new questions. You have to see, my 2 questions in this thread is related, that's why i posted it continueously.

If they are unrelated, sure i will help this forum to get another post for C++ forum. :-)

thanks for your tips tho.

happy holiday

[horace1]

Here i have next question, related to question above i think.
----------------


Now this time i stuck here with "...comprises a Point and ....". What does it means to you?

I know those question should be easy but sometimes it does confusing ppl with unclear definition or explanation.

any ideas?
(i think it should similar to the code i posted before.)

I would have thought a vector would have two Points for the vector start and end or does Vector mean something else in this context?

[nickyeng]

I would have thought a vector would have two Points for the vector start and end or does Vector mean something else in this context?

vector class is unrelated to STL vector. It just a simple class.

actually the answer wont be the compiled-well code. What to do is just write the code for each questions. Forget it about compiled-well mind..!

i'm not sure my code is correct, and there is no other ppl here can provide me with the better one, so i just follow my code.

thanks for the help anyway.

[horace1]

vector class is unrelated to STL vector. It just a simple class.

thanks for the help anyway.

I am not talking about STL vectors but about a vector in 2D coordinate space - one would have a x1, y1 start Point and a x2, y2 end Point
I am not sure what you mean by a vector?

[nickyeng]

I am not talking about STL vectors but about a vector in 2D coordinate space - one would have a x1, y1 start Point and a x2, y2 end Point
I am note what you mean by a vector?

no idea. cos teacher wont say and i have the question only.

forget about this question.


End of thread.

[RedSon]

Vectors in the mathematical sense have an origin (x,y) a direction (maybe a slope or something to that effect) and a magnitude. You can give the origin and another point in the line of the vector and a magnitude but you can choose any other point on the vector line. Vectors don't have end points, they are rays of a certain magnitude.