1. C# Programming: From Problem Analysis to Program Design1 Repeating Instructions C# Programming: From Problem Analysis to Program Design 3rd Edition 6

2. Part II C# Programming: From Problem Analysis to Program Design2

3. 3 For Loop Pretest form of loop (like the while) –Considered specialized form of while statement Usually associated with counter-controlled types –Packages initialization, test, and update all on one line General form is: for (statement; conditional expression; statement) statement; Interpreted as: for (initialize; test; update) statement;

4. C# Programming: From Problem Analysis to Program Design4 For Loop ( continued ) Figure 6-8 Flow of control with a for statement

5. C# Programming: From Problem Analysis to Program Design5 For Loop ( continued ) For loop is executed as shown in the numbered steps Figure 6-9 Steps of the for statement

6. C# Programming: From Problem Analysis to Program Design6 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++) { Console.WriteLine("{0}\t{1}\t{2}", counter, Math.Pow(counter,2), Math.Pow(counter,3)); } Replace above while loop with for loop below – does same

7. C# Programming: From Problem Analysis to Program Design7 For Loop ( continued ) counter out of SCOPE Figure 6-10 Syntax error

8. C# Programming: From Problem Analysis to Program Design8 Ways to Initialize, Test, and Update For Statements for (int counter = 0, val1 = 10; counter < val1; counter++) 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 0; counter++, j += 3)

9. C# Programming: From Problem Analysis to Program Design9 Ways to Initialize, Test, and Update For Statements ( continued ) Floating-point variables can be used –for initialization, expressions, and update for (double d = 15.0; d < 20.0; d += 0.5) { Console.Write(d + “\t”); } –The output produced 15 15.5 16 16.5 17 17.5 18 18.5 19 19.5

10. C# Programming: From Problem Analysis to Program Design10 Ways to Initialize, Test, and Update For Statements ( continued ) Can change the loop control variable inside the loop for (double d = 15.0; d < 20.0; d += 0.5) { Console.Write(d + “\t”); d += 2.0 } –The output produced 1517.5 C# lets you change the conditional expression endValue inside the loop body – BUT, be careful here

11. C# Programming: From Problem Analysis to Program Design11 Foreach Statement Used to iterate or move through a collection –Array (Chapter 7) General form foreach (type identifier in expression) statement; Expression is the collection (array) Type is the kind of values found in the array –Restriction on foreach—cannot change values Access to the elements is read-only

12. C# Programming: From Problem Analysis to Program Design12 Do…While Statements Posttest General form do { statement; } while ( conditional expression); Figure 6-12 Do…while loop

13. C# Programming: From Problem Analysis to Program Design13 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

14. C# Programming: From Problem Analysis to Program Design14 Nested Loops Loop can be nested inside an outer loop –Inner nested loop is totally completed before the outside loop is tested a second time 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

15. C# Programming: From Problem Analysis to Program Design15 Recursion Technique where a method calls itself repeatedly until it arrives at the solution Algorithm has to be developed so as to avoid an infinite loop –To write a recursive solution, an algorithm has to be developed so as to avoid an infinite loop Have to identify a base case Base case is the simplest form of the solution

16. C# Programming: From Problem Analysis to Program Design16 Recursive Call Figure 6-15 Recursive evaluation of n!

17. C# Programming: From Problem Analysis to Program Design17 Unconditional Transfer of Control Break –Used with switch statement –Place in the body of a loop to provide immediate exit Be careful (Single Entry/Single Exit) Continue –When reached, a new iteration of the nearest enclosing while, do…while, for, or foreach statement is started Other jump statements –goto, throw, and return Use sparingly

18. C# Programming: From Problem Analysis to Program Design18 Deciding Which Loop to Use Sometimes a personal choice Body of the do…while always executed at least once –Posttest type Numeric variable being changed by a consistent amount – for statement While statement can be used to write any type of loop –Pretest type

19. C# Programming: From Problem Analysis to Program Design19 LoanApplication Example Figure 6-16 Problem specification for the LoanApplication example

20. C# Programming: From Problem Analysis to Program Design20 LoanApplication Example ( continued )

21. C# Programming: From Problem Analysis to Program Design21 LoanApplication Example ( continued ) Figure 6-17 Prototype for the LoanApplication example

22. C# Programming: From Problem Analysis to Program Design22 LoanApplication Example ( continued ) Figure 6-18 Class diagrams

23. C# Programming: From Problem Analysis to Program Design23 Formulas Used for LoanApplication Example

24. C# Programming: From Problem Analysis to Program Design24 Properties for LoanApplication Example

25. C# Programming: From Problem Analysis to Program Design25 Pseudocode – Loan Class Figure 6-19 Behavior of Loan class methods

26. C# Programming: From Problem Analysis to Program Design26 Pseudocode – LoanApp Class Figure 6-20 Behavior of LoanApp class methods

27. C# Programming: From Problem Analysis to Program Design27 Desk Check of LoanApplication Example

28. C# Programming: From Problem Analysis to Program Design28 /* 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

29. C# Programming: From Problem Analysis to Program Design29 // 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; }

30. C# Programming: From Problem Analysis to Program Design30 // Remaining properties defined for each fields as shown on Slide #50 // 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;

31. C# Programming: From Problem Analysis to Program Design31 for (int month = 1; month <= numPayments; month++) { CalculateMonthCharges(month, numPayments); aSchedule += month + "\t“ + monthInterest.ToString("F") + "\t“ + principal.ToString("F") + "\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;

32. C# Programming: From Problem Analysis to Program Design32 if (month == numPayments) { principal = balance; payment = balance + monthInterest; } else { principal = payment - monthInterest; } balance -= principal; } // Calculates interest paid over the life of the loan public void DetermineTotalInterestPaid( ) { totalInterestPaid = 0; balance = loanAmount;

33. C# Programming: From Problem Analysis to Program Design33 for (int month = 1; month <= numPayments; month++) { CalculateMonthCharges(month, numPayments); totalInterestPaid += monthInterest; }

34. C# Programming: From Problem Analysis to Program Design34 /* 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

35. C# Programming: From Problem Analysis to Program Design35 do { GetInputValues(out loanAmount, out interestRate, out years); Loan ln = new Loan(loanAmount, interestRate, years); ln.DeterminePaymentAmount( ); Console.WriteLine( ); Console.WriteLine(ln.ReturnAmortizationSchedule()); ln.DetermineTotalInterestPaid( ); Console.WriteLine("Payment Amount: {0:C}", ln.PaymentAmount); Console.WriteLine("Interest Paid over Life of Loan: " + ln.TotalInterestPaid); Console.Write("Do another Calculation? (Y or N)"); inValue = Console.ReadLine( ); anotherLoan = Convert.ToChar(inValue); } while ((anotherLoan == 'Y')|| (anotherLoan == 'y')); }

36. C# Programming: From Problem Analysis to Program Design36 // Prompts user for loan data static void GetInputValues(out double loanAmount, out double interestRate, out int years) { string sValue; Console.Write("Loan Amount: "); sValue = Console.ReadLine( ); loanAmount = Convert.ToDouble(sValue); Console.Write("Interest Rate (as a decimal value): "); sValue = Console.ReadLine( ); interestRate = Convert.ToDouble(sValue); Console.Write("Number of Years to Finance: "); sValue = Console.ReadLine( ); years = Convert.ToInt32(sValue); }

37. C# Programming: From Problem Analysis to Program Design37 LoanApplication Example Figure 6-21 LoanApplication output

38. Coding Standards Guidelines for Placement of Curly Braces Spacing Conventions Advanced Loop Statement Suggestions C# Programming: From Problem Analysis to Program Design38

39. C# Programming: From Problem Analysis to Program Design39 Chapter Summary Major strengths of programming languages attributed to loops Types of loops –while Counter-controlled State-controlled Sentinel-controlled –for –foreach –do…while

40. C# Programming: From Problem Analysis to Program Design40 Chapter Summary ( continued ) Conditional expressions used with loops Nested loops Unconditional transfer of control Which use loop structures? –Loop structures for different types of applications