04 – conditional execution

Mark Dixon

04 – Conditional Execution

Mark Dixon

Questions: Expressionsa) What is the result of:

10 * Int(3.1973265765)

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 6

30

2

3

(15 / 3) * 6

Mark Dixon

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

Example: AddNum v1<html> <head><title>Add Numbers</title></head> <body> <input type="text" id="txtNum1" /><br /> <input type="text" id="txtNum2" /><br /> <input type="button" id="btnAdd" value="Add" /> <p id="lblResult"></p> </body></html>

<script type="text/vbscript"> Sub btnAdd_OnClick() lblResult.InnerText = txtNum1.Value + txtNum2.Value End Sub</script>Doesn't work!

Mark Dixon

Types of Information• Numeric (numbers) 29

(integer/whole) 56.23 (decimal/real)

• String (text) "Hello there!""BOO"

• Pictures (numbers)

• Sound (numbers)

Mark Dixon

AddNum problem• The + operator works with:

– numbers, and

– text

• Text input boxes store text

23 + 16 39

"23" + "16" "2316"

double quotes enclose text

Mark Dixon

String Functions CInt("63") convert to integer result is 63

Left("boo",2) left string result is "bo"

Right("hello",3) right string result is "llo"

Mid("hello",2,2) middle string result is "el"

Len("S Smith") length result is 7

Space(5) spaces result is " "

Mark Dixon

String Expressions

Mark Dixon

String Expressions & Errors "What is " + txtN1.Value + " times "

"What is twice " txtN1.Value + "?"

"What is 6 minus " + + txtN1.Value + "?"

dataoperator

data data

operator

ERROR! missing data

ERROR! missing operator

Mark Dixon

Questions: String Expressionsa) 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

Example: AddNum v2<html> <head><title>Add Numbers</title></head> <body> <input type="text" id="txtNum1" /><br /> <input type="text" id="txtNum2" /><br /> <input type="button" id="btnAdd" value="Add" /> <p id="lblResult"></p> </body></html>

<script type="text/vbscript"> Sub btnAdd_OnClick() lblResult.InnerText = CInt(txtNum1.Value) + CInt(txtNum2.Value) End Sub</script>

Mark Dixon

Example: Text Shift<html> <head><title>Text Shift</title></head> <body> <p id="parH"></p> </body></html>

<script type="text/vbscript"> 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</script>

Mark Dixon

Adaptive Behaviour• So far

– every statement always executed in sequence

• Often necessary for software to– change behaviour under different circumstances

Mark Dixon

Example: Multiplication TestSPECIFICATION

• 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-functionalshould be interesting, colourful, and easy to use

Mark Dixon

Example: Multiplication Test v1<html> <head><title>Multiply</title></head> <body> <p>What is 5 times 3?</p> <input type="text" id="txtAns" /><br /> <input type="button" id="btnAns" value="Check" /> <p id="lblComment"></p> </body></html>

<script type="text/vbscript"> 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</script>

Mark Dixon

Example: Multiplication Test v1

Mark Dixon

Example: Multiplication Test v1.1<html> <head><title>Multiply</title></head> <body> <embed id="sndFanfare" src="Fanfare.wav" hidden="true" autoplay="False"></embed> <p>What is 5 times 3?</p> <input type="text" id="txtAns" /><br /> <input type="button" id="btnAns" value="Check" /> <p id="lblComment"></p> </body></html>

<script type="text/vbscript"> 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</script>

Mark Dixon

If Then statements• Use the following syntax (pattern):

If condition Then statementblockEnd If

• For example:If txtAge.value < 18 Then document.bgColor = "Red"End If

Mark Dixon

If Then Else statements• Use the following syntax (pattern):

If condition1 Then statementblock-1Else statementblock-2End If

• For example:If txtAge.value < 18 Then document.bgColor = "Red"Else document.bgColor = "Blue"End If

Mark Dixon

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 less than>= is greater than or equal to<= is less than or equal to<> is not equal to

Mark Dixon

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

Logical Operators

• And True when both items are True(picMain.vSpace > 5) AND (picMain.vSpace < 35) (true)(picMain.vSpace < 10) AND (picMain.vSpace > 55) (false)(picMain.vSpace > 6) AND (picMain.vSpace < 23) (false)(picMain.vSpace >=6) AND (picMain.vSpace <= 23) (true)

• Or True when either item is True(picMain.vSpace = 23) OR (picMain.vSpace = 11) (true)(picMain.vSpace < 10) OR (picMain.vSpace > 55) (false)

• Not True when item is FalseNot (picMain.vSpace = 23) (false)

Use to join conditions (assume picMain.vSpace is 23):

Mark Dixon

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

Example: Student Loan<html> <head><title>Student Loan Repayment Calculator</title></head> <body> <center><font size="+2"><b>Student Loan Repayment Calculator</b></font></center> <input type="text" id="txtIncome" /> <input type="button" id="btnCalc" value="Calculate" /> <p id="lblPayment"></p> </body></html>

<script type="text/vbscript"> Sub btnCalc_OnClick() lblPayment.innertext = (txtIncome.value - 15000) * 0.09 End Sub</script>

SLC

Mark Dixon

Example: Student Loan (v2)<html> <head><title>Student Loan Repayment Calculator</title></head> <body> <center><font size="+2"><b>Student Loan Repayment Calculator</b></font></center> <input type="text" id="txtIncome" /> <input type="button" id="btnCalc" value="Calculate" /> <p id="lblPayment"></p> </body></html>

<script type="text/vbscript"> Sub btnCalc_OnClick() If txtIncome.value > 15000 Then lblPayment.innertext = "£" + CStr((txtIncome.value - 15000) * 0.09) Else lblPayment.innertext = "You pay nothing (£0.00)!" End If End Sub</script>

Mark Dixon

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

Example: Ball Char (v2)<html> <head><title>Ball Char</title></head> <body style="background-color: Lime;"> <img id="picBall" src="BallChar.jpg" style="position: absolute;" /> </body></html>

<script type="text/vbscript"> Sub Window_OnLoad() Window.SetInterval "MoveBallRight", 50 End Sub Sub MoveBallRight() picBall.style.pixelLeft = picBall.style.pixelLeft + 5 End Sub</script>

Mark Dixon

Example: Ball Char (v2.1)<html> <head><title>Ball Char</title></head> <body style="background-color: Lime;"> <img id="picBall" src="BallChar.jpg" style="position: absolute;" /> </body></html>

<script type="text/vbscript"> 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</script>

Mark Dixon


<script type="text/vbscript"> 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</script>

Mark Dixon



Sub MoveBallRight() If (picBall.style.pixelLeft + 5) < (document.body.clientwidth - picBall.width) Then picBall.style.pixelLeft = picBall.style.pixelLeft + 5 End If End Sub</script>

Mark Dixon



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</script>

Mark Dixon

Example: Ball Char (v2.5)• Bounce from side to side, with sound:

Mark Dixon

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

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

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

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

Tutorial Exercises: Student Loan• LEARNING OBJECTIVE:


• 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

Tutorial Exercises: BallChar• LEARNING OBJECTIVE:


• 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

04 – conditional execution

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