Exercise 10.3 (Completed)

1. (Review) Determine whether the following statements are true or false:
a. A constructor method must have the same name as its class.
True
b. A class can have only one constructor method.
False
c. A class can have only one default constructor method.
True
d. A default constructor can be supplied only by the compiler.
False
e. A default constructor can have no parameters or all parameters must have default values.
True
f. A constructor must be declared for each class.
False
g. A constructor must be declared with a return type.
False
h. A constructor is called automatically each time an object is created.
True
i. A class can have only one destructor method.
True
j. A destructor must have the same name as its class, preceded by a tilde (~).
True
k. A destructor can have default arguments.
False
l. A destructor must be declared for each class.
True
m. A destructor must be declared with a return type.
False
n. A destructor is called automatically each time an object goes out of existence.
True
o. Destructors aren’t useful when the class contains a pointer data member.
False

2. (Desk check) For Program 10.3, what date is initialized for object c if the declaration
Date c(15); is used instead of the declaration Date c(20090515L);?

The date is 15/04/12

3. (Modify) Modify Program 10.3 so that the only data member of the class is a long integer
named yyyymmdd. Do this by substituting the declaration long yyyymmdd; for these existing
declarations:
int month;
int day;
int year;
Using the same constructor prototypes currently declared in the class declaration section,
rewrite them so that the Date(long) method becomes the default constructor, and the
Date(int, int, int) method converts a month, day, and year into the correct form for the
class data members.

class Date
{
private:
	int month;
	int day;
	int year;
public:
	Date(int, int, int);   // constructor
	Date(long = 20120704);           // another constructor
	void showDate();      // member method to display a date
};

4. (Program) a. Construct a Time class containing integer data members seconds, minutes,
and hours. Have the class contain two constructors: The first should be a default constructor
having the prototype Time(int, int, int), which uses default values of 0 for each data
member. The second constructor should accept a long integer representing a total number of
seconds and disassemble the long integer into hours, minutes, and seconds. The final member
method should display the class data members.

class Time
{
private:
	int seconds;
	int minutes;
	int hours;
public:
	Time(int = 0, int = 0, int = 0);   // constructor
	Time(long);           // another constructor
	void showTime();      // member method to display a Time
};
// class implementation section
Time::Time(int ss, int mm, int hh)
{
	seconds = ss;
	minutes = mm;
	hours = hh;
}
Time::Time(long hhmmss)
{
	hours = int(hhmmss / 10000.0);   // extract the year
	minutes = int((hhmmss - hours * 10000.0) / 100.00); // extract the month
	seconds = int(hhmmss - hours * 10000.0 - minutes * 100.0); // extract the day
}
void Time::showTime()
{
	cout << "The Time is ";
	cout << setfill('0')
		<< setw(2) << hours << ' '
		<< setw(2) << minutes << ' '
		<< setw(2) << seconds; // extract the last 2 year digits
	cout << endl;
	return;
}

b. Include the class written for Exercise 4a in the context of a complete program.

#include "stdafx.h" 
#include <iostream>
#include <iomanip>
using namespace std;
// class declaration section
class Time
{
private:
	int seconds;
	int minutes;
	int hours;
public:
	Time(int = 0, int = 0, int = 0);   // constructor
	Time(long);           // another constructor
	void showTime();      // member method to display a Time
};
// class implementation section
Time::Time(int ss, int mm, int hh)
{
	seconds = ss;
	minutes = mm;
	hours = hh;
}
Time::Time(long hhmmss)
{
	hours = int(hhmmss / 10000.0);   // extract the year
	minutes = int((hhmmss - hours * 10000.0) / 100.00); // extract the month
	seconds = int(hhmmss - hours * 10000.0 - minutes * 100.0); // extract the day
}
void Time::showTime()
{
	cout << "The Time is ";
	cout << setfill('0')
		<< setw(2) << hours << ' '
		<< setw(2) << minutes << ' '
		<< setw(2) << seconds; // extract the last 2 year digits
	cout << endl;
	return;
}
int main()
{
	Time a, b(4, 1, 19), c(103515L); // declare three objects
	a.showTime();           // display object a's values
	b.showTime();           // display object b's values
	c.showTime();           // display object c's values
	system("PAUSE");
	return 0;
}

5. (Program) a. Construct a class named Student consisting of an integer student ID number,
an array of five double-precision grades, and an integer representing the total number of grades
entered. The constructor for this class should initialize all Student data members to 0.
Included in the class should be member methods to 1) enter a student ID number, 2) enter a
single test grade and update the total number of grades entered, and 3) compute an average
grade and display the student ID followed by the average grade.

Done!!

b. Include the class constructed in Exercise 5a in the context of a complete program. Your
program should declare two objects of type Student and accept and display data for the two
objects to verify operation of the member methods.

#include <iostream>
#include <iomanip>
using namespace std;
// class declaration section
class Student
{
private:
	int IDnum;
	double grade;
	int total;
public:
	Student(int = 0, double = 0, int = 0);   // constructor
	void averageGrade(int);           // another constructor
	void displayIDAvg();      // member method to display a Student
};
// class implementation section
Student::Student(int ID, double grad, int tot)
{
	IDnum = ID;
	total = tot;
	grade = grad;

	

}

void Student::averageGrade( int grades){
	
	
	int result = grades;
		
	
		int average = result ;
		cout << average << endl;
		return;
}
void Student::displayIDAvg()
{
	cout << "The Student is ID & Average is ";
	cout << IDnum << endl;
	averageGrade(100);

	cout << endl;
	return;
}
int main()
{
	Student a, b(374, 98, 1); // declare three objects
	b.displayIDAvg();
	system("PAUSE");
	return 0;
}

6. (Modify) a. In Exercise 4, you were asked to construct a Time class. For this class, include a
tick() method that increments the time by one second. Test your method to ensure that it
increments time into a new minute and a new hour correctly.

void Time::tick(){

	if (minutes != 60 && seconds == 60) {
		minutes++;
		seconds = 1;

	}
	else if (minutes == 60 && seconds == 60){

		hours++;
		seconds = 1;
		minutes = 1;

	}
	else if (seconds < 60 && minutes != 60){
     	seconds++;
	}
	cout << hours << ':' << minutes << ':' << seconds << endl;
}

b. Modify the Time class written for Exercise 6a to include a detick() method that decrements
the time by one second. Test your method to ensure that it decrements time into a
prior hour and into a prior minute correctly.

void Time::detick(){

	if (minutes != 1 && seconds == 1) {

		minutes--;

		seconds = 59;

	}

	else if (minutes == 1 && seconds == 1){

		--hours;
		seconds = 59;
		minutes = 59;

	}
	else if (seconds < 60 && minutes != 60){
		seconds--;

	}

	cout << hours<< ':' << minutes << ':' << seconds << endl;

}

7. (Program) a. Construct a class named Coord containing two double-precision data members
named xval and yval, used to store a point’s x and y values in Cartesian coordinates. The
member methods should include constructor and display methods and a method named
convToCartesian(). The convToCartesian() method should accept two double-precision
numbers named r and theta representing a point in polar coordinates and convert them into
Cartesian coordinates. For conversion from polar to Cartesian coordinates, use these formulas:
x = r cos (theta)
y = r sin (theta)

Done!!

b. Include the program written for Exercise 7a in a working C++ program.

#include <iostream>
#include <iomanip>
#include <cmath>

using namespace std;

// class declaration section

class Coord

{
private:
	double xval;
	double yval;

public:
	Coord(double = 20, double = 30);   // constructor
	void convToCartesian(double,double);
	void showCoord();      // member method to display a Coord
	
};

// class implementation section

Coord::Coord(double xx, double yy)

{
	xval = xx;
	yval = yy;
}
void Coord::convToCartesian(double r,double theta){

	double x = r * cos(theta);
	double y = r * sin(theta);
	cout << x << ',' << y << endl;
	return;
}

void Coord::showCoord(){
	cout << xval << ',' << yval << endl;
}


int main()
{
	Coord a, b(4, 1), c; // declare three objects
	
	a.showCoord();
	b.showCoord();
	c.showCoord();

	a.convToCartesian(10, 23);
	b.convToCartesian(24, 45);
	c.convToCartesian(23, 12);
	
	system("PAUSE");

	return 0;
}