Mark Dixon 1 05 – Conditional Execution. Mark Dixon 2 Admin: Test (next week) In class test –teaching week 6 50 minutes short answer (5 - 6 words) currently

Mark Dixon 1

05 – Conditional Execution

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Admin: Test (next week)• In class test

– teaching week 6

• 50 minutes

• short answer (5 - 6 words)

• currently 10% of overall mark

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Admin Test• Current

– Coursework• C1 25%• C2 25%

– Test• T1 10%• T2 10%

– Examination 30%

• Proposed– Coursework

• C1 25%• C2 25%

– Test• T1 25%• T2 25%

- Felt that exam duplicated other assessment- looking to change now – student feedback has influence (but outcome is not certain)- email: no response taken as No

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Can't touch this• Student work from previous year:

based on work done by Daniel Thornton & David Orrock

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Questions• name: event, object, property, event handler,

operator, function, expression<script language="vbscript"> Sub window_onLoad() imgHammer.style.posLeft = 500 imgHammer.style.posTop = 100 imgHammer.style.height = 100 imgHammer.style.width = 75 sndPlayer.src = "Hammer.wav" End Sub

Sub imgHammer_onMouseOver() imgHammer.style.posLeft = Rnd() * (document.body.clientWidth - imgHammer.width) imgHammer.style.posTop = Rnd() * (document.body.clientHeight - imgHammer.height) End Sub</script>

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Questions: Data Typesa) What is the result of:

Mid("George Boole", 5, 4)

b) What is put in parRes?txtPetName.value = "George"parRes.innerText = Right(txtPetName.value, 3)

c) What is put in parRes?txtPetName.value = "George"parRes.innerText = Right("txtPetName", 3)

ge B

rge

ame

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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 (If) to make your code

more adaptable

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Adaptive Behaviour• So far

– every statement always executed in sequence

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

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Example: Student Loan<html> <head> <title>Student Loan Repayment Calculator</title> <meta http-equiv="x-ua-compatible" content="IE=10" /> </head> <body> <center><font size="+2"><b>Student Loan Repayment Calculator</b></font></center> <input id="txtIncome" type="text" /> <input id="btnCalc" type="button" value="Calculate" /> <p id="parPayment"></p> </body></html>

<script language="vbscript"> Sub btnCalc_onClick() parPayment.innerText = (txtIncome.value - 21000) * 0.09 End Sub</script> Problem: if salary < 21000 gives negative payment

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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

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Example: Multiplication Test v1<html> <head> <title>Multiply</title> <meta http-equiv="x-ua-compatible" content="IE=10" /> </head> <body> <p>What is 5 times 3?</p> <input id="txtAns" type="text" /><br /> <input id="btnAns" type="button" value="Check" /> <p id="parComment"></p> </body></html>

<script language="vbscript"> Sub btnAns_OnClick() If txtAns.value = 15 Then document.bgColor = "yellow" parComment.innerText = "Correct, well done!" Else document.bgColor = "cyan" parComment.innerText = "Sorry, try again" End If End Sub</script>

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Example: Multiplication Test v1

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Example: Multiplication Test v1

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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

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

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

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

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George Boole• 1815 (Lincoln, UK) – 1864

• Invented Boolean algebra– key concept in computing– boolean datatype:

• false (stored as 0)• true (stored as 1 or -1)

• Condition – Boolean expression, evaluates to true or false

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Conditions: Relational Operators• conditions 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

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Conditions: Examples (literal)• Using literals:

34 = 34

34 = 12

34 > 4

18 <= 18

"hello" > "zoo"

true

false

true

true

false

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Conditions: Examples (symbolic)• Using symbols (controls' properties):

Assume that:picMain.style.posLeft is 2300

picMain.style.posLeft = 2300

picMain.style.posLeft = 2309

picMain.style.posLeft <> 189

picMain.style.posLeft > 1900

true

false

true

true

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Conditions: Errors• Are the following valid:

– 23 > 30

– 66 15

– 23 <

– picBat.style.posLeft > 1000

– < picBat.style.posTop

missing (relational) operator

missing data

missing data

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Questions: Conditions• What is the result of (picMain.style.posLeft is 5589):


• Write an expression to check if:

the posLeft of picMain is larger than 167

• Write an expression to check if:

picMain posTop is more than picBall posTop

true


picMain.style.posTop > picBall.style.posTop

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Example: Student Loan (v2)<html> <head> <title>Student Loan Repayment Calculator</title> <meta http-equiv="x-ua-compatible" content="IE=10" /> </head> <body> <center><font size="+2"><b>Student Loan Repayment Calculator</b></font></center> <input id="txtIncome" type="text" /> <input id="btnCalc" type="button" value="Calculate" /> <p id="parPayment"></p> </body></html>

<script language="vbscript"> Sub btnCalc_onClick() If txtIncome.value > 21000 Then parPayment.innerText = "£" & ((txtIncome.value - 21000) * 0.09) Else parPayment.innerText = "You pay nothing (£0.00)!" End If End Sub</script>

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If statements: Errors

If txtNum.value > 5 Then If txtNum.value = 4 Then document.bgColor = "green"

End If

If picMan.width > 5 document.bgColor = "red"End If

missing Then keyword

missing End If

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Example: Ball Char (v2)• Functional Decomposition

• Incremental Development

• Get ball char to move automatically:– 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

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Example: Ball Char (v2)<html> <head> <title>Ball Char</title> <meta http-equiv="x-ua-compatible" content="IE=10" /> </head> <body> <img id="picBall" src="BallChar.gif" style="position: absolute;" /> </body></html>

<script language="vbscript"> Sub window_onLoad() window.setInterval "MoveBallRight()", 500 picBall.style.posLeft = 0 picBall.style.posTop = 60 End Sub

Sub MoveBallRight() picBall.style.posLeft = picBall.style.posLeft + 5 End Sub</script>

Procedure name

Interval(in milliseconds: 1000 = 1s)

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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

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Example: Ball Char (v2.1)<html> <head> <title>Ball Char</title> <meta http-equiv="x-ua-compatible" content="IE=10" /> </head> <body style="background-color: Lime;"> <img id="picBall" src="BallChar.jpg" style="position: absolute;" /> </body></html>

<script language="vbscript"> Sub window_onLoad() window.setInterval "MoveBall()", 500 picBall.style.posLeft = 0 picBall.style.posTop = 60 End Sub Sub MoveBall() If picBall.style.posLeft < document.body.clientwidth Then picBall.style.posLeft = picBall.style.posLeft + 5 End If End Sub</script>

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<script language="vbscript"> Sub window_onLoad() window.setInterval "MoveBall()", 500 picBall.style.posLeft = 0 picBall.style.posTop = 60 End Sub

Sub MoveBall() If (picBall.style.posLeft + picBall.width) < document.body.clientWidth Then picBall.style.posLeft = picBall.style.posLeft + 5 End If End Sub</script>

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<script language="vbscript"> Sub window_onLoad() window.setInterval "MoveBall()", 500 picBall.style.posLeft = 0 picBall.style.posTop = 60 End Sub

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

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Example: Ball Char (v2.4)• Bounce from side to side, with sound:

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Example: Pizza Delivery

A Pizza shop provides a delivery service. If the delivery is within five miles of the shop, then no delivery fee is charged. If the cost of the goods is less than £10 then a £3 delivery fee is charged, otherwise a £1.50 delivery fee is charged.

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Decision Trees• Natural language

– ambiguous & difficult to follow

• Decision trees– express same information clearly

distance <= 5 miles

value >= £10

Free

£1.50

£3.00

Y

N Y

N

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Example: Pizza Delivery<html> <head><title>Delivery</title></head> <body> <p>Distance: <input type="text" id="txtDist" /><br /> Cost: <input type="text" id="txtCost" /><br /> <input type="button" id="btnCalc" value="Calc" /> </p> <p id="parCharge"></p> </body></html>

<script language="vbscript"> Sub btnCalc_onClick() If txtDist.value <= 5 Then parCharge.innerText = "Delivery Charge: £0.00" Else If txtCost.value >= 10 Then parCharge.innerText = "Delivery Charge: £1.50" Else parCharge.innerText = "Delivery Charge: £3.00" End If End If End Sub</script>

• Nested If statements– one if

inside another if

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Logical Operators

• And True when both items are TruepicMain.vSpace > 5 AND picMain.vSpace < 35 truepicMain.vSpace < 10 AND picMain.vSpace > 55 falsepicMain.vSpace > 6 AND picMain.vSpace < 23 falsepicMain.vSpace >= 6 AND picMain.vSpace <= 23 true

• Or True when either item is TruepicMain.vSpace = 23 OR picMain.vSpace = 11 truepicMain.vSpace < 10 OR picMain.vSpace > 55 false

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

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

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Logical Operators: Errors

If picMan.width > 5 And < 10 Then document.bgColor = "red"End If missing

data

If picMan.width > 5 And picMan.width < 10 Then document.bgColor = "red"End If

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Tutorial Exercises: Multiplication• LEARNING OBJECTIVE:

use if statement to perform conditional execution

• Task 1: Get the Multiplication v1 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

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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).

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Tutorial Exercises: Ball Char• LEARNING OBJECTIVE:

to assign a value to a object's property,• using combination of literal values, operators, functions, and

identifiers

• Task 1: get the ball char (v2) example working• Task 2: add a button that resets the ball char's horizontal position to 0• Task 3: add a text box that allows the user to control the speed of the ball

character. HINT: Currently, the ball char will always move 5 pixels at a time.

• Task 4: add a button that stops the ball char moving. HINT: button should put 0 into the text box

• Task 5: add two buttons – one for fast and one for slow• Task 6: add two more buttons – one for fast backwards and one for slow

backwards• Task 7: make it bounce off both sides of the client area (screen).• Task 8: hide the speed text box

HINT: this should happen when the window loads, using style.visibility• Task 9: make the Ball Character blink when the mouse moves over it• Task 10: play a sound when the ball character is clicked

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Tutorial Exercises: Pizza Delivery• LEARNING OBJECTIVE:

use nested if statements to perform conditional execution

• Task 1: Get the Pizza Delivery example (from the lecture) working.

Documents

Mark Dixon 1 05 – Conditional Execution. Mark Dixon 2 Admin: Test (next week) In class test –teaching week 6 50 minutes short answer (5 - 6 words) currently