Repeating Instructions - csuohio.edugrail.cba.csuohio.edu/~matos/notes/ist-211/csNotes/9781285096261... · Repeating Instructions ... Sentinel-Controlled Loop • Exact number of

C# Programming: From Problem Analysis to Program Design

1

Repeating

Instructions


4th Edition

6


2

Chapter Objectives


3

Chapter Objectives (continued)


4

Chapter Objectives (continued)


5

Why Use A Loop?


6

Using the while Statement

→ →

7

while Statement

Figure 6-1 Pretest loop


8

Counter-Controlled Loop

9


Example /* SummedValues.cs Author: Doyle */

int sum = 0; //Line 1

int number = 1; //Line 2

while (number < 11) //Line 3

{ //Line 4

sum = sum + number; //Line 5

number++; //Line 6

} //Line 7

Console.WriteLine("Sum of values " //Line 8

+ "1 through 10" //Line 9

+ " is " + sum); //Line 10


10


(continued)


(continued)

Console.Write("Enter the beginning value: ");

inValue = Console.ReadLine();

if (int.TryParse(inValue, out startValue) == false)

Console.WriteLine("Invalid input - 0 recorded for start value");

Console.Write("Enter the last value: ");


if (int.TryParse(inValue, out endValue) == false)

Console.WriteLine("Invalid input - 0 recorded for end value");

while (startValue < endValue + 1)

11

Last number should

be added to the total.


(continued) while (startValue < endValue + 1)


12


(continued)

13

14

Sentinel-Controlled Loop

/* InputValuesLoop.cs Author: Doyle */

static void Main( )

{

string inValue = ""; //Initialized to empty body

Console.Write("This program will let you enter value after value.");

Console.WriteLine("To Stop, enter -99");

while (inValue != "-99")

{

Console.WriteLine("Enter value (-99 to exit)");


}

Console.ReadKey( ); }

15


Example

16


(continued)

17


(continued)

/* PrimeRead.cs Author: Doyle */

static void Main( )

{

string inValue = ""; //Initialized to null

int sum = 0,

intValue;

Console.Write("This program will let you enter");

Console.Write(" value after value. To Stop, enter");

Console.WriteLine(" -99");


inValue = Console.ReadLine(); // Priming read

18


(continued) while (inValue != "-99")

{

if (int.TryParse(inValue, out intValue) == false)

Console.WriteLine("Invalid input - 0 stored in intValue");

sum += intValue;



}

Console.WriteLine("Total values entered {0}", sum);

Console.ReadKey( );

}


19

Windows Applications Using

Loops

20

State-Controlled Loops

21

State-Controlled Loops Example bool moreData = true;

while (moreData)

{ // moreData is updated inside the loop condition changes

if (MessageBox.Show("Do you want another number ?",

"State Controlled Loop", MessageBoxButtons.YesNo,

MessageBoxIcon.Question) == DialogResult.No)

// Test to see if No clicked

{

moreData = false;

} // End of if statement

// More loop body statements

} // End of while loop

22

For Loop

for (statement; conditional expression; statement) statement;

for (initialize; test; update) statement;

23

For Loop (continued)

24


For loop statements

are executed in the

order shown by the

numbered steps

25

Comparison of While and For

Statement int counter = 0;

while (counter < 11)

{

Console.WriteLine("{0}\t{1}\t{2}", counter,

Math.Pow(counter,2), Math.Pow(counter,3));

counter++;

}

for (int counter = 0; counter < 11; counter++)

{



}

Replace

above

while

loop

with for

loop

below –

does

same

26

Comparison of While and For

Statement

int counter = 0;

while (counter < 11)

{

Console.WriteLine("{0}\t{1}\t{2}", counter, Math.Pow(counter,2), Math.Pow(counter,3));

counter++;

}

for (int counter = 0; counter < 11; counter++)

{



}

Replace

above

while

loop

with for

loop

below –

does

same

Output from Examples 6.11 & 6.12 0 0 0

1 1 1

2 4 8

3 9 27

4 16 64

5 25 125

6 36 216

7 49 343

8 64 512

9 81 729

10 100 1000

27

Output from both the

while and for loop

examples compared on the previous

slide

28


Figure 6-10 Syntax error

counter is

out of

SCOPE


29

30

Ways to Initialize, Test, and Update For Statements

for (int counter = 0, val1 = 10; counter < val1; counter++)

// Compound initialization

for ( ; counter < 100; counter+=10) // No initialization

for (int j = 0; ; j++) // No conditional expression

for ( ; j < 10; counter++, j += 3) // Compound update

for (int aNum = 0; aNum < 101; sum += aNum, aNum++);

// Null loop body

for (int j = 0,k = 10; j < 10 && k > 0; counter++, j += 3)

// Compound test (conditional expression)

for (double d = 15.0; d < 20.0; d += 0.5)

{

Console.Write(d + "\t");

}

31

Ways to Initialize, Test, and

Update For Statements (continued)

32

Ways to Initialize, Test, and

Update For Statements (continued)

for (double d = 15.0; d < 20.0; d += 0.5)

{

Console.Write(d + "\t");

d += 2.0

}

C# lets you change the

conditional expression

endValue inside the loop

body – BUT, be careful

here

33

Foreach Statement

foreach (type identifier in expression)

statement;

• type

34

Do…While Statements

do

{

statement;

}

while ( conditional expression);

Figure 6-12 Do…while loop

35

Do…While Example

int counter = 10;

do // No semicolon on this line

{

Console.WriteLine(counter + "\t" + Math.Pow(counter, 2));

counter--;

}

while (counter > 6);

The output of this code is:

10 100

9 81

8 64

7 49

Do…While Example (continued)

36

No semicolon after do, but curly braces are required…when you have more than one statement between do and while

37

Nested Loops

int inner;

for (int outer = 0; outer < 3; outer++)

{

for(inner = 10; inner > 5; inner --)

{

Console.WriteLine("Outer: {0}\tInner: {1}", outer, inner);

}

}

15 lines

printed

38

Nested Loops

Review NFactorial Example

NFactorial Example

do //Line 5

{ //Line 6

n = InputN( ); //Line 7

CalculateNFactorialIteratively(n, out result); //Line 8

DisplayNFactorial(n, result); //Line 9

moreData = PromptForMoreCalculations( ); //Line 10

} //Line 11

while (moreData = = "y" || moreData = = "Y"); //Line 12

39

Nfactorial Example (continued)

public static void CalculateNFactorialIteratively(int n, out int result)

{ //Line 20

result = 1; //Line 21

for (int i = n; i > 0; i--) //Line 22

{ //Line 23

result *= i; //Line 24

} //Line 25

} //Line 26

40

41

Recursion

42

Recursive Call

Figure 6-15 Recursive evaluation of n!

public static int Fact(int n) { if (n == 1 || n == 0) return 1; else return (n * Fact(n-1)); }

43

Unconditional Transfer of

Control • break

switch

• continue

while

– goto throw return

goto

Break Statement int total = 0;

for (int nValue = 0; nValue < 10; nValue++)

{

if (nValue == 5)

{

break;

}

total += nValue;

Console.Write(nValue + "\t");

}

Console.WriteLine("\nTotal is equal to {0}.", total);

44

The output is:

0 1 2 3 4

Total is equal to 10.

Continue Statement int total = 0;

for (int nValue = 0; nValue < 10; nValue++)

{

if (nValue % 2 == 0)

{

continue;

}

total += nValue;

Console.Write(nValue + "\t");

}

Console.WriteLine("\nTotal is equal to {0}.", total);

45

The output is:

0 3 5 7 9

Total is equal to 25.


46

Deciding Which Loop to Use


47

LoanApplication Example

Figure 6-16 Problem specification for LoanApplication example


48

LoanApplication Example (continued)

Table 6-3 Instance field members for the Loan class


(continued)


49

Table 6-4 Local variables for the LoanApp class


50

Formulas Used for



51


Figure 6-17 Prototype for the LoanApplication example


52


Figure 6-18 Class diagrams


53

Properties for LoanApplication

Example

Table 6-5 Properties for the Loan class


54

Pseudocode –

Loan Class

Figure 6-19 Behavior of

Loan class methods


55

Figure 6-20 Behavior of LoanApp class methods

Pseudocode –LoanApp Class


56

Desk Check of LoanApplication

Example

Figure 6-6 LoanApp test values


57

/* Loan.cs

* Creates fields for the amount of loan, interest rate, and number of years.

* Calculates amount of payment and produces an amortization schedule.

*/

using System;

using System.Windows.Forms;

namespace Loan

{

public class Loan

{

private double loanAmount;

private double rate;

private int numPayments;

private double balance;

private double totalInterestPaid;

private double paymentAmount;

private double principal;

private double monthInterest;

Loan class


58

// Constructors

public Loan( ) { }

public Loan(double loan, double interestRate, int years)

{

loanAmount = loan;

if (interestRate < 1)

rate = interestRate;

else // In case directions aren't followed

rate = interestRate / 100; // convert to decimal

numPayments = 12 * years;

totalInterestPaid = 0;

}

// Property accessing payment amount

public double PaymentAmount {

get

{

return paymentAmount;

}

}


59

// Remaining properties defined for each field

// Determine payment amount based on number of years,

// loan amount, and rate

public void DeterminePaymentAmount( )

{

double term;

term = Math.Pow((1 + rate / 12.0), numPayments);

paymentAmount = ( loanAmount * rate / 12.0 * term)

/ (term - 1.0);

}

// Returns a string containing an amortization table

public string ReturnAmortizationSchedule()

{

string aSchedule = "Month\tInt.\tPrin.\tNew";

aSchedule += "\nNo.\tPd.\tPd.\tBalance\n";

balance = loanAmount;

60

for (int month = 1; month <= numPayments; month++)

{

CalculateMonthCharges(month, numPayments);

aSchedule += month + "\t" + monthInterest.ToString("N2")

+ "\t“ + principal.ToString("N2") + "\t"

+ balance.ToString("C") + "\n";

}

return aSchedule;

}

// Calculates monthly interest and new balance

public void CalculateMonthCharges(int month, int numPayments)

{

double payment = paymentAmount;

monthInterest = rate / 12 * balance;

if (month == numPayments)

{

principal = balance;

payment = balance + monthInterest;

}

else

{

principal = payment - monthInterest;

}

balance -= principal;

}


61

// Calculates interest paid over the life of the loan

public void DetermineTotalInterestPaid( )

{

totalInterestPaid = 0;

balance = loanAmount;

for (int month = 1; month <= numPayments; month++)

{

CalculateMonthCharges(month, numPayments);

totalInterestPaid += monthInterest;

}

}

}

}


62

/* LoanApp.cs

* Used for testing Loan class. Prompts user for input values.

* Calls method to display payment amount and amortization

* schedule. Allows more than one loan calculation. */

using System;

using System.Windows.Forms;

namespace Loan

{

class LoanApp

{

static void Main( )

{

int years;

double loanAmount;

double interestRate;

string inValue;

char anotherLoan = 'N';

LoanApp

class


63

do

{

GetInputValues(out loanAmount, out interestRate, out years);

Loan ln = new Loan(loanAmount, interestRate, years);

Console.WriteLine( );

Console.Clear( );

Console.WriteLine(ln);

Console.WriteLine( );

Console.WriteLine(ln.ReturnAmortizationSchedule( ));

Console.WriteLine("Payment Amount: {0:C}", ln.PaymentAmount);

Console.WriteLine("Interest Paid over Life of Loan: {0:C} ",

ln.TotalInterestPaid);

Console.Write("Do another Calculation? (Y or N)");

inValue = Console.ReadLine( );

anotherLoan = Convert.ToChar(inValue);

}

while ((anotherLoan == 'Y')|| (anotherLoan == 'y'));

}

64

// Prompts user for loan data

static void GetInputValues(out double loanAmount,

out double interestRate,

out int years)

{

Console.Clear( );

loanAmount = GetLoanAmount( );

interestRate = GetInterestRate( );

years = GetYears( );

}

65

// Prompts user for loan amount data

public static double GetLoanAmount( )

{

string sValue;

double loanAmount;

Console.Write("Please enter the loan amount: ");

sValue = Console.ReadLine();

while (double.TryParse(sValue, out loanAmount) == false)

{

Console.WriteLine("Invalid data entered for loan amount");

Console.Write("\nPlease re-enter the loan amount: ");

sValue = Console.ReadLine();

}

return loanAmount;

}

}


66

Figure 6-21

LoanApplication

output

Coding Standards


67

Resources

68


69

Chapter Summary


70

Chapter Summary (continued)

Documents

Repeating Instructions - csuohio.edugrail.cba.csuohio.edu/~matos/notes/ist-211/csNotes/9781285096261... · Repeating Instructions ... Sentinel-Controlled Loop • Exact number of