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How to use classes

closed account (SEwCM4Gy)
Hi everyone,

So this is the code that my professor gave us to start with, and I'm not really sure where to start with Part 1 of the assignment. I would really appreciate help with getting started with this assignment; I think after an explanation from someone with more experience, I'll have an idea of what to do.

For Part 1, I need to define the functions indicated in the class Point, so that I'm able to find the distance between 2 points. The problem for me, is I have absolutely no clue how to define the class functions so that it makes sense... It would be a huge help if I knew what each specific class function is doing. Thanks!

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 #include <iostream>
#include <vector>
#include <cmath>

using namespace std;

/**************************************************************
* Here are included the definitions of the class and functions
* Do not modify this part
*************************************************************/


class Point
{
public:
	Point(double xparam, double yparam);
	Point();
	double getX();
	double getY();
	void setX(double xparam);
	void setY(double yparam);
	void display();
private:
	double x;
	double y;
};

struct Triangle
{
	Point p1;
	Point p2;
	Point p3;
};


double distancepoints(Point& p1, Point& p2);
int closest(Point& start, vector<Point>& village);
Triangle three_closest(Point& start, vector<Point>& village);
void displayTriangle(Triangle T);
Point suggest(Triangle T);


/*******************************************
* End of definitions here
*******************************************/





// ----------------------------------------------------------------------
int main()
{

	/****************************************************************************
	* Part 1  Creating 5 points representing  5 houses in the village
	and adding them to village vector
	This code will work once you implement the member functions of the Point Class
	and the distance function
	***************************************************************************/



	Point p1(1, 5), p2(1.25, 0.5), p3(3, 2), p4(5, 6.25), p5(5.5, 1.5), location(4, 3);
	vector<Point> village;
	village.push_back(p1);
	village.push_back(p2);
	village.push_back(p3);
	village.push_back(p4);
	village.push_back(p5);



	cout << "For the starting location ";
	location.display();
	cout << " in the village : ";



	for (unsigned int i = 0; i < village.size(); i++)
	{
		village[i].display();

	}


	cout << "\n the distances from the houses are :" << endl;
	for (unsigned int i = 0; i < village.size(); i++)
	{
		cout << "   ";
		village[i].display();
		cout << " --> " << distancepoints(village[i], location) << endl;
	}


	/*******************************************
	* End of Part1
	*******************************************/


	/*************************************************************
	* Part2
	This code will work once you implement the closest function
	**************************************************************/

	cout << "\n the closest point is ";
	Point  unluckiest = village[closest(location, village)];
	unluckiest.display();

	/*******************************************
	* End of Part2
	*******************************************/


	/*************************************************************
	* Part3 and 4
	This code will work once you implement the three_closest function
	and the suggest function
	**************************************************************/

	cout << "," << endl << " The three closes points are  ";
	Triangle unlucky = three_closest(location, village);
	displayTriangle(unlucky);


	cout << "\n and the new suggested location for the landfill ";
	Point landfill = suggest(unlucky);
	landfill.display();
	cout << "." << endl;

	/*******************************************
	* End of Parts 3 and 4
	*******************************************/


	return 0;
}







/*****************************************************
* Your Code here


Implement the member functions of the class Point
Point(double xparam, double yparam);
Point();
double getX();
double getY();
void setX(double xparam);
void setY(double yparam);
the function display() is already implemented
*****************************************************/


void Point::display()
{
	cout << " (" << x << ", " << y << ") ";
}




/*****************************************************
* Your Code here

Implement the following functions
double distancepoints(Point& p1, Point& p2);
int closest(Point& start, vector<Point>& village);
Point suggest(Triangle T )

the functions displayTriangle(),
three_closest(Point& start, vector<Point>& village)
are already implemented
*****************************************************/




Triangle three_closest(Point& start, vector<Point>& village)
{
	int p;
	Triangle T;
	p = closest(start, village);
	T.p1 = village[p];
	village.erase(village.begin() + p);
	p = closest(start, village);
	T.p2 = village[p];
	village.erase(village.begin() + p);
	p = closest(start, village);
	T.p3 = village[p];

	return T;
}

void displayTriangle(Triangle T)
{
	T.p1.display();
	T.p2.display();
	T.p3.display();
}




/*******************************************
* End of your code here
*******************************************/
mutexe (2372)
closed account (SEwCM4Gy)
How do I go about defining the distance function?
I know that to calculate the distance between two points (x1, y1) and (x2, y2), you will use the distance formula, so I tried this:

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double distancepoints(Point& p1, Point& p2)
{
return sqrt(pow(p1, 2) + pow(p2, 2));
}


However, the pow function isn't working.
wildblue (1505)
p1 and p2 are Point objects - pow doesn't know how to handle a custom class. I think you mean to use the x and y data members of the Point objects to use in this distance formula?

http://www.purplemath.com/modules/distform.htm

dhayden (5798)
You might want to write the member functions of class Point first, just to get them out of the way.

As for the distance() function, go one step at a time. Given two points (x1,y1) and (x2,y2), what is the mathematical formula for the distance between them? Don't worry about the Point class yet, just worry about the math.

Once you have the formula right, you can worry about translating it into C++ code with the Point class.

closed account (SEwCM4Gy)
Alright so what I tried now is this:

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double distancepoints(Point& p1, Point& p2)
{
	double d1 = p1.getX();
	double d2 = p2.getX();
	double d3 = p1.getY();
	double d4 = p2.getY();
	return sqrt(pow((d1-d2), 2) + pow((d3-d4), 2));
}


This makes more sense to me; I had to implement the "get" functions to individually get the x and y coordinates to use in the distance formula. Thanks!
closed account (SEwCM4Gy)
I'm slightly confused with the "closest" function, what I got is this, but it isn't returning the coordinate I want that is closest to starting point.


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int closest(Point& start, vector<Point>& village)
{
	int flag;
	for (unsigned int i = 1; i < village.size(); i++)
	{
		if (village[0] < village[i])
			flag = i;
	}
	return flag;
}
ne555 (10692)
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if (village[0] < village[i])
	flag = i;
¿how do you compare two points?
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