act4

---main.cpp---
#include <iostream>
#include "class.h"

using namespace std;

int choice, size;
double numbers[20];
double disp;

void collectNumbers();

int main()
{
	Calc c;

	do{
		system("CLS");
		cout<<"Welcome to calculator C++ version\n";
		cout<<"[1] Sum\n";
		cout<<"[2] Mean\n";
		cout<<"[3] Variance\n";
		cout<<"[4] Standard Deviation\n";
		cout<<"[5] EXIT\n";
		cout<<"Please input the number of your choice: ";
		cin>>choice;

		switch(choice)
		{
			case 1:
				collectNumbers();
				disp = c.getSum(numbers, size);
				cout<<"The sum of your numbers is " <<disp;
				system("PAUSE");
				break;

			case 2:
				collectNumbers();
				disp = c.getSum(numbers, size);
				disp = c.getMean(disp, size);
				cout<<"The mean of your numbers is " <<disp;
				system("PAUSE");
				break;

			case 3:
				collectNumbers();
				disp = c.getSum(numbers, size);
				disp = c.getMean(disp, size);
				disp = c.getVariance(numbers, disp, size);
				cout<<"The variance of your numbers is " <<disp;
				system("PAUSE");
				break;

			case 4:
				collectNumbers();
				disp = c.getSum(numbers, size);
				disp = c.getMean(disp, size);
				disp = c.getVariance(numbers, disp, size);
				disp = c.getStandardDeviation(disp);
				cout<<"The standard deviation of your numbers is " <<disp;
				system("PAUSE");
				break;
		}
	}while(choice != 5);

	cout<<"Closing program...";
	system("PAUSE");
	return 0;
}

void collectNumbers()
{
	cout<<"How many numbers do you want to compute: ";
	cin>>size;

	for(int i = 1; i <= size; i++)
	{
		cout<<"Please input number: ";
		cin>>numbers[i];
		cout<<endl;
	}
}


---members.cpp---
#include <iostream>
#include "class.h"

using namespace std;

Calc::Calc()
{
	double input[20];
	double mean = 0;
	double var = 0;
	double tempSum = 0;
	double ans = 0;
	int cnt = 0;
}

double Calc::getSum(double input[], int cnt)
{
	for(int i = 1; i <= cnt; i++)
	{
		ans = ans + input[i];
	}

	return ans;
}

double Calc::getMean(double tempSum, int cnt)
{
	ans = 0;

	ans = tempSum/cnt;

	return ans;
}

double Calc::getVariance(double input[], double mean, int cnt)
{
	for(int i = 1; i <= cnt; i++)
	{
		input[i] = (input[i] - mean) * (input[i] - mean);
	}

	ans = getSum(input, cnt);
	ans = getMean(ans, cnt);

	return ans;
}

double Calc::getStandardDeviation(double var)
{
	ans = var/3;

	if(var <= 0)
	{
		return 0;
	 }

	for(int i = 0; i < 32; i++)
	{
		ans = (ans + var / ans) / 2;
	}

	return ans;
}


---class.h---
#include <iostream>

using namespace std;

class Calc
{
	private:
		double input[];
		double mean, var, tempSum, ans;
		int cnt;

	public:
		Calc();
		double getSum(double input[], int cnt);
		double getMean(double tempSum, int cnt);
		double getVariance(double input[], double mean, int cnt);
		double getStandardDeviation(double var);
};