mark dixon, socce soft 131page 1 07 – iterative execution
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Mark Dixon, SoCCE SOFT 131 Page 1
07 – Iterative Execution
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Coursework 1 (Test) - Results
StudentNumber
Score(max 50)
Classification is for guidance only
Please feel free to come and discuss your results with me
10071281 43.510068515 42.010006434 37.0
10041425 16.5 10080929 35.510075490 16.5 246751 24.5 10063595 33.0 10073337 35.0
<40% (fail) <50% (3) <60% (2:2) <70% (2:1) >=70% (1)
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Coursework 1 (Test) - Debrief• Range of marks normal
• Failure rate quite high – 30% (3 / 10)– not unusual for this module– recoverable if corrective action is taken
• Please feel free to discuss marks in tutorial
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Coursework 1 (Test) - Problems• Answer question:
– Name a variable: Dim x x
• Conditional expressions: x > 4– used in conditional statements:
If picMain.height < 0 Then
• Parameters – data given to functions: x = Int(34.56) + 34.56 + sqr(b)
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Session Aims & Objectives• Aims
– To introduce the main concepts involved in getting the machine to perform repetitive tasks.
• Objectives,by end of this week’s sessions, you should be able to:
– To be able to implement code that does repetitive tasks, using looping structures:
• known limits (for loop)• unknown limits (do loop)
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Example: Hello v0
<html> <head><title>Hello</title></head> <body> <input id=btnHello type=button value=Hello /> <p id=lblHello></p> </body></html>
<script language=vbscript>Option Explicit Sub btnHello_OnClick() lblHello.innerHTML = lblHello.innerHTML & "Hello<br>" End Sub</script>
• 1 user click: 1 Hello (1 line of code)
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Example: Hello v1
<script language=vbscript>Option Explicit
Sub btnHello_OnClick() lblHello.innerHTML = lblHello.innerHTML & "Hello<br>" lblHello.innerHTML = lblHello.innerHTML & "Hello<br>" lblHello.innerHTML = lblHello.innerHTML & "Hello<br>" lblHello.innerHTML = lblHello.innerHTML & "Hello<br>" lblHello.innerHTML = lblHello.innerHTML & "Hello<br>" lblHello.innerHTML = lblHello.innerHTML & "Hello<br>" lblHello.innerHTML = lblHello.innerHTML & "Hello<br>" lblHello.innerHTML = lblHello.innerHTML & "Hello<br>" lblHello.innerHTML = lblHello.innerHTML & "Hello<br>" lblHello.innerHTML = lblHello.innerHTML & "Hello<br>" End Sub</script>
• 1 user click: 10 Hellos (10 lines of code)Lots of lines
imagine 300 Hellos
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Example: Hello v2
<script language=vbscript>Option Explicit
Sub btnHello_OnClick() Dim h For h = 1 to 10 lblHello.innerHTML = lblHello.innerHTML & "Hello<br>" Next End Sub</script>
• 1 user click: 10 Hellos (4 lines of code)
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For ... Next statement• repeat code known number of times
– reduces length of code
– easier to change
• Syntax:
For variable = start To end statementblock Next
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Advantages• Less code:
• This makes program:– Easier to read– Easier to change (imagine 500 Hellos)
Option Explicit
Sub btnGo_OnClick()Dim h For h = 1 To 10 lblHello.innerHTML = lblHello.innerHTML & "Hello<br>" NextEnd Sub
Option Explicit
Sub btnGo_OnClick()lblHello.innerHTML = lblHello.innerHTML & "Hello<br>"lblHello.innerHTML = lblHello.innerHTML & "Hello<br>"lblHello.innerHTML = lblHello.innerHTML & "Hello<br>"lblHello.innerHTML = lblHello.innerHTML & "Hello<br>"lblHello.innerHTML = lblHello.innerHTML & "Hello<br>"lblHello.innerHTML = lblHello.innerHTML & "Hello<br>"lblHello.innerHTML = lblHello.innerHTML & "Hello<br>"lblHello.innerHTML = lblHello.innerHTML & "Hello<br>"lblHello.innerHTML = lblHello.innerHTML & "Hello<br>"lblHello.innerHTML = lblHello.innerHTML & "Hello<br>"End Sub
Hello v1 Hello v2
10lines
4 lines
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• Real Power of loops– using counter variable
– do something slightly different each time
• Example: Dim numDim tottot = 0For num = 1 To 5 tot = tot + numNextlblRes.InnerText = tot
Example: Total
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Example: Total
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Question: For … Next• What does the following code produce:
Dim counter For counter = 1 To 10 lblNums.InnerText = lblNums.InnerText & counter Next
• What does the following code produce:Dim i For i = 24 To 8 Step -2 lblNums.InnerText = lblNums.InnerText & i & i * 2 Next
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Example: Letter Count <script language=vbscript> Option Explicit
Sub btnCount_OnClick() Dim pos Dim count Dim char count = 0 For pos = 1 To Len(txtWords.value) char = Mid(txtWords.value, pos, 1) If char = "e" Then count = count + 1 End If Next lblCount.innerText = count End Sub</script>
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Example: Shades<script language="vbscript">Option Explicit
Sub btnShow_OnClick() Const stTag = "<span style=""background: #" Dim h, p, msg, red msg = txtMsg.value h = "" red = 255 For p = 1 To Len(msg) h = h + stTag + Hex(red) + "0000"">" h = h + Mid(msg, p, 1) h = h + "</span>" red = red - 5 Next divTones.innerHTML = h End Sub</script>
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Do ... Loop statement
• repeat code unknown number of times– more flexible than For
– slower than For
• Syntax:Do [{While|Until} condition] [statementblock]Loop
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Example: Do … Loop• Can do everything a For … Loop can:
Dim I Dim ii = 1Do While i <= 10 For i = 1 To 10 lblN.InnerText = i picN.InnerText =
i i = i + 1Loop Next
• And more:Dim ii = 1Do While i < 10 lblN.innertext = i If (i / 2) = Int(i / 2) then i = i + 1 Else i = i + 3 End If Loop
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Question: Do … Loop• What does the following produce:Dim num num = 20 Do While num > -12 lblDo.InnerText = lblDo.InnerText & num num = num - 1.5 Loop
• What does the following produce:Dim num num = 6 Do Until num > 4 num = num + 5 lblDo.InnerText = lblDo.InnerText & num Loop
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Tutorial Exercise: Hello• Task 1: Get the Hello Example (from the
lecture) working.
• Task 2: Modify your page so that it uses a variable to temporarily build to html.
• Task 3: Modify your page so that the user can control how many 'Hellos' appear.
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Tutorial Exercise: Letter Count• Task 1: Get the Letter Count Example (from
the lecture) working.• Task 2: Modify your Letter Count page, so
that the user can control which letter is counted.Hint: You will need a text box for the user to type a letter into.
• Task 3: Modify your Letter Count program, so that the user cannot type more than one letter in the letter text box.Hint: Use the text box’s change event, and the len function.
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Tutorial Exercise: Vowel Count• Task 1: Create a new page that counts the
number of vowels (a, e, i, o, u) in a piece of text. Hint: similar to the letter count example.
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Tutorial Exercise: Shades• Task 1: Get the shades example from the
lecture working.
• Task 2: Modify the page so that it puts a space in between each letter.
• Task 3: Change the program so that it uses shades of another colour instead.
• Task 4: Create a new page that selects random shades of your selected colour. Hint: use the Rnd function.
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Tutorial Exercise: Chess Board• Task 1: Use one for loop inside another to
create a chess board.
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