/***************************************************************************
Program:	A2Q1.cpp


Purpose: This program implements mathematical operations on two 3D vectors.
		 The user is asked to input 3-dimension vector v1 and v2 and real a
		 real number a. A loop is entered to ask the user which operation
		 he/she would like to perform on the vectors and the result is 
		 output to the screen.
****************************************************************************/

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

using namespace std;

// Function Prototypes
void getVector(vector<double> &v);
void showVector(const vector<double> &v);

int main(){
    vector<double> v1(3);		// create vector v1 of size 3
	vector<double> v2(3);		// create vector v2 of size 3
	vector<double> result(3);	// create vector for results
	double a, ans = 0.0;
	int choice;
	
	// get user input for vector v1
	cout << "\nPlease enter 3-dimensional vector v1:\n";
    getVector(v1);
	
	// get user input for vector v2
	cout << "\nPlease enter 3-dimensional vector v2:\n";
    getVector(v2);

	// get user input for number a
	cout << "\nPlease enter real number a:\n";
	cin >> a;

	// loop to perform operations on vectors
	do{
		cout << "\nWhat operation would you like to do on the vectors?\n"
			<< "1. Addition (v1+v2).\n"
			<< "2. Subtraction (v1-v2).\n"
			<< "3. Multiply v1 by a constant (a*v1 = v1*a).\n"
			<< "4. Dot Product (v1*v2).\n"
			<< "5. Magnitude (|v1| = sqrt(x1*x1+y1*y1+z1*z1)).\n"
			<< "6. Exit program.\n\n";
		cin >> choice;  // get user option

		switch(choice){
			case 1:  // addition
				cout << "\nThe sum of v1+v2 is: ";
				for (unsigned int i = 0; i < v1.size(); i++)
                    result[i] = v1[i] + v2[i];
				showVector(result);
				cout << endl << endl;
				break;
			case 2:  // subtraction
				cout << "\nThe difference of v1-v2 is: ";
				for (unsigned int i = 0; i < v1.size(); i++)
                    result[i] = v1[i] - v2[i];
				showVector(result);            
				cout << endl << endl;
				break;
			case 3:  // constant * vector
				cout << "\nThe result of a*v1 = v1*a is: ";
				for (unsigned int i = 0; i < v1.size(); i++)
                    result[i] = a*v1[i];
				showVector(result);
                cout << endl << endl;
				break;
			case 4:	// dot product
                for (unsigned int i = 0; i < v1.size(); i++)
                    ans = ans + v1[i]*v2[i];
				cout << "\nThe dot product is " << ans << endl << endl;
				break;
			case 5:	// magnitude
                for (unsigned int i = 0; i < v1.size(); i++)
                    ans = ans + v1[i]*v1[i];
                ans = sqrt(ans);
				cout << "\nThe magnitude is " << ans << endl << endl;
				break;
			default: // exit switch
                if (choice != 6)
                    cout << "That is not a valid choice. Please choose again.\n\n";
		}
		ans = 0.0; // reset variable
	}while(choice!=6); // exit program
}

/****************************************************************************
Function:		getVector
Purpose:		Prompt user to input the vector
Parameters:		vector of size double
Return Value:	NONE
****************************************************************************/
void getVector(vector<double> &v){
	for (unsigned int i=0; i<v.size(); i++)
        cin >> v[i];
}

/****************************************************************************
Function:		showVector
Purpose:		To display the vector
Parameters:		const vector of size double
Return Value:	NONE
****************************************************************************/
void showVector(const vector<double> &v){
	for (unsigned int i = 0; i < v.size(); i++)
	    cout << v[i] << " ";
}