Mark Dixon Page 1 04 – Conditional Execution

Mark Dixon Page 2 Questions: Expressions a)What is the result of: 10 * Int( ) b)How many functions are in the following: Int(12.472) * Sqr(9)) + 8 / 2 c)How many operators are in the following: Int(12.472) * Sqr(9)) + 8 / 2 d)Write an expression to: divide 15 by 3 and multiply the result by (15 / 3) * 6

Mark Dixon Page 3 Session Aims & Objectives Aims –to introduce the main concepts involved in getting the computer to act differently under different circumstances Objectives, by end of this week’s sessions, you should be able to: –evaluate and generate conditional expressions –use conditional statements to make your code more adaptable

Mark Dixon Page 4 Example: AddNum v1 Add Numbers Sub btnAdd_OnClick() lblResult.InnerText = txtNum1.Value + txtNum2.Value End Sub Doesn't work!

Mark Dixon Page 5 Types of Information Numeric (numbers)29 (integer/whole) (decimal/real) String (text)"Hello there!" "BOO" Pictures (numbers) Sound (numbers)

Mark Dixon Page 6 AddNum problem The + operator works with: –numbers, and –text Text input boxes store text "23" + "16" "2316" double quotes enclose text

Mark Dixon Page 7 String Functions CInt("63") convert to integer result is 63 Left("boo",2) left stringresult is "bo" Right("hello",3) right stringresult is "llo" Mid("hello",2,2) middle stringresult is "el" Len("S Smith") lengthresult is 7 Space(5) spacesresult is " "

Mark Dixon Page 8 String Expressions

Mark Dixon Page 9 String Expressions & Errors "What is " + txtN1.Value + " times " "What is twice " txtN1.Value + "?" "What is 6 minus " + + txtN1.Value + "?" data operator data operator ERROR! missing data ERROR! missing operator

Mark Dixon Page 10 Questions: String Expressions a)What is the result of: Mid("what is the time?", 3, 4) b)What is the result of: "23" + "18" + Left("bob",1) + Right("sal",2) c)Write an expression to: convert "16" to a number d)Write an expression to: give the first two letters of "Mr John Smith" "at i" "2318bal" CInt("16") Left("Mr John Smith", 2)

Mark Dixon Page 11 Example: AddNum v2 Add Numbers Sub btnAdd_OnClick() lblResult.InnerText = CInt (txtNum1.Value) + CInt (txtNum2.Value) End Sub

Mark Dixon Page 12 Example: Text Shift Text Shift Sub Window_OnLoad() parH.innertext = "Hello There" + Space(100) Window.SetInterval "TextShift", 50 End Sub Sub TextShift() parH.innertext = Mid(parH.innertext,2) + Left(parH.innerText,1) End Sub

Mark Dixon Page 13 Adaptive Behaviour So far –every statement always executed in sequence Often necessary for software to –change behaviour under different circumstances

Mark Dixon Page 14 Example: Multiplication Test SPECIFICATION User Requirements –A primary school teacher wants to test the multiplication skills of her children. Software Requirements –Functional: –display a multiplication question –allow the user to type a response –check the response and provide feedback –Non-functional should be interesting, colourful, and easy to use

Mark Dixon Page 15 Example: Multiplication Test v1 Multiply What is 5 times 3? Sub btnAns_OnClick() If txtAns.Value = 15 Then document.bgcolor = "yellow" lblComment.innertext = "Correct, well done!" Else document.bgcolor = "cyan" lblComment.innertext = "Sorry, try again" End If End Sub

Mark Dixon Page 16 Example: Multiplication Test v1

Mark Dixon Page 17 Example: Multiplication Test v1

Mark Dixon Page 18 Example: Multiplication Test v1.1 Multiply What is 5 times 3? Sub btnAns_OnClick() If txtAns.Value = 15 Then document.bgcolor = "yellow" lblComment.innertext = "Correct, well done!" sndFanfare.Play Else document.bgcolor = "cyan" lblComment.innertext = "Sorry, try again" End If End Sub

Mark Dixon Page 19 If Then statements Use the following syntax (pattern): If condition Then statementblock End If For example: If txtAge.value < 18 Then document.bgColor = "Red" End If

Mark Dixon Page 20 If Then Else statements Use the following syntax (pattern): If condition1 Then statementblock-1 Else statementblock-2 End If For example: If txtAge.value < 18 Then document.bgColor = "Red" Else document.bgColor = "Blue" End If

Mark Dixon Page 21 Conditions & Relational Operators Conditions – expression, evaluates to: –true(stored as –1) –false(stored as 0) contain relational operators: =is equal to >is greater than =is greater than or equal to is not equal to

Mark Dixon Page 22 Examples: Conditions Using literals: (34 = 34)(evaluates to true) (34 = 12)(evaluates to false) (34 > 4)(evaluates to true) (18 <=18)(evaluates to true) Using controls' properties: Assume that picMain.hSpace is 2300 (picMain.hSpace = 2300) (true) (picMain.hSpace = 2309 (false) (picMain.hSpace <> 189 (true) (picMain.hSpace > 1900 (true)

Mark Dixon Page 23 Logical Operators AndTrue when both items are True (picMain.vSpace > 5) AND (picMain.vSpace 55) (false) (picMain.vSpace > 6) AND (picMain.vSpace =6) AND (picMain.vSpace <= 23) (true) OrTrue when either item is True (picMain.vSpace = 23) OR (picMain.vSpace = 11) (true) (picMain.vSpace 55) (false) NotTrue when item is False Not (picMain.vSpace = 23) (false) Use to join conditions (assume picMain.vSpace is 23):

Mark Dixon Page 24 Exercise: Conditions What is the result of (picMain.hSpace is 5589): (picMain.hSpace > 4400) What is the result (txtAge.value is 19, txtSalary.value is 10787): (txtAge.Value < 21) AND (txtSalary.Value < 10787) Write an expression to check if: picMain.hSpace is larger than 167 Write an expression to check if: picMain.vSpace is larger than picBall.vSpace true false (picMain.hSpace > 167) (picMain.vSpace > picBall.vSpace)

Mark Dixon Page 25 Example: Student Loan Student Loan Repayment Calculator Student Loan Repayment Calculator Sub btnCalc_OnClick() lblPayment.innertext = (txtIncome.value ) * 0.09 End Sub SLC

Mark Dixon Page 26 Example: Student Loan (v2) Student Loan Repayment Calculator Student Loan Repayment Calculator Sub btnCalc_OnClick() If txtIncome.value > Then lblPayment.innertext = "£" + CStr((txtIncome.value ) * 0.09) Else lblPayment.innertext = "You pay nothing (£0.00)!" End If End Sub

Mark Dixon Page 27 Example: Ball Char Functional Decomposition Incremental Development Get ball char to bounce horizontally: –get ball char to appear on left of page –get ball char to move right on page (user click) –get ball char to move right on page automatically –get ball char to stop at end –get ball char to change direction

Mark Dixon Page 28 Example: Ball Char (v2) Ball Char Sub Window_OnLoad () Window.SetInterval "MoveBallRight", 50 End Sub Sub MoveBallRight () picBall.style.pixelLeft = picBall.style.pixelLeft + 5 End Sub

Mark Dixon Page 29 Example: Ball Char (v2.1) Ball Char Sub Window_OnLoad() Window.SetInterval "MoveBallRight", 50 End Sub Sub MoveBallRight() If picBall.style.pixelLeft < document.body.clientwidth Then picBall.style.pixelLeft = picBall.style.pixelLeft + 5 End If End Sub

Mark Dixon Page 30 Example: Ball Char (v2.2) Ball Char Sub Window_OnLoad() Window.SetInterval "MoveBallRight", 50 End Sub Sub MoveBallRight() If picBall.style.pixelLeft < ( document.body.clientwidth - picBall.width ) Then picBall.style.pixelLeft = picBall.style.pixelLeft + 5 End If End Sub

Mark Dixon Page 31 Example: Ball Char (v2.3) Ball Char Sub Window_OnLoad() Window.SetInterval "MoveBallRight", 50 End Sub Sub MoveBallRight() If (picBall.style.pixelLeft + 5) < (document.body.clientwidth - picBall.width) Then picBall.style.pixelLeft = picBall.style.pixelLeft + 5 End If End Sub

Mark Dixon Page 32 Example: Ball Char (v2.4) Ball Char Sub Window_OnLoad() Window.SetInterval "MoveBallRight", 50 End Sub Sub MoveBallRight() If (picBall.style.pixelLeft + 5) < (document.body.clientwidth - picBall.width) Then picBall.style.pixelLeft = picBall.style.pixelLeft + 5 Else Window.SetInterval "MoveBallLeft", 50 End If End Sub Sub MoveBallLeft () picBall.style.pixelLeft = picBall.style.pixelLeft - 5 End Sub

Mark Dixon Page 33 Example: Ball Char (v2.5) Bounce from side to side, with sound:

Mark Dixon Page 34 Tutorial Exercises: AddNum LEARNING OBJECTIVE: use function to convert string (text) to integer (number) Task 1: get the addnum examples (v1 and v2) working

Mark Dixon Page 35 Tutorial Exercises: Text Shift LEARNING OBJECTIVE: use string manipulation functions Task 1: get the Text Shift example (from the lecture) working Task 2: modify your program so that the text goes the other way.

Mark Dixon Page 36 Tutorial Exercises: Initials LEARNING OBJECTIVE: use string manipulation functions Task 1: create a new site with two text boxes (surname and forenames), and a button (initials). When the button is clicked the first character from each text box (i.e. the person's initials) should be displayed.

Mark Dixon Page 37 Tutorial Exercises: Multiplication LEARNING OBJECTIVE: use if statement to perform conditional execution Task 1: Get the Multiplication v1 and v1.1 examples (from the lecture) working. Task 2: Modify your program so that the text box is disabled after the answer is checked Task 3: Modify your program so that it makes a suitable sound when the user gets the answer right/wrong. Sound files are in the resources section of the web-site

Mark Dixon Page 38 Tutorial Exercises: Student Loan LEARNING OBJECTIVE: use if statement to perform conditional execution Task 1: Get the Student Loan v1 and v2 examples (from the lecture) working. Task 2: Modify your program so that it calculates and displays monthly income and repayment amounts (as well an annual).

Mark Dixon Page 39 Tutorial Exercises: BallChar LEARNING OBJECTIVE: use if statement to perform conditional execution Task 1: Get the BallChar example (from the lecture) working. You will need to work out the code for v2.5 – use the previous code for inspiration. Task 2: Modify your program so that the Ball Character blinks when the mouse moves over it Task 3: Modify your program to play a sound when the ball character is clicked