Repetition

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Chapter 6

• Repetition

2
Comparing While and Until Loops

• The Do While Loop executes while the condition
  is true
• The Do Until.. Loop executes until the condition
  is true
• Both can be used to create any type of loop

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Processing List of Data with Loops

• Open a file as we did previously
• File can be of any length
• EOF Function Tells us if we have read to the
  end of a file.
• Checks for the end-of-file marker.

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EOF Function Syntax

• EOF(n) where n is the reference number for the
  file.
• If there are more records to be read, EOF is
  False.
• When the end-of-file marker is reached EOF
  becomes True.

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Flowchart for a Do While Loop
Open Filename.txt
EOF?
Yes
No
Get next item of data
Close Filename.txt
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Example of EOF Phone.txt

• "Bert", "123-4567"
• "Ernie", "987-6543"
• "Grover", "246-8321"
• "Oscar", "135-7900"

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Example of EOF

• Open Phone.txt for Input As 1
• Do While Not EOF(1)
• Input 1, nom, phoneNum
• picOutput.Print nom, phoneNum
• Loop
• Close 1

Phone.txt
"Bert", "123-4567" "Ernie", "987-6543" "Grover",
"246-8321" "Oscar", "135-7900"
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Processing List of Data with Loops Looking for
a Specific Element

• Open the file
• File may be of any length
• Compare each element against the value of that
  being sought
• EOF Function Tells us if we have read to the
  end of a file.

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Processing List of Data with Loops Looking for
a Specific Element

• Private Sub cmdDisplay_Click()
• Dim nom As String, phoneNum As String
• Open App.Path "\PHONE.TXT" For Input As 1
• Do While (nom ltgt txtName.Text) And (Not EOF(1))
• Input 1, nom, phoneNum
• Loop
• Close 1
• picNumber.Cls
• If nom txtName.Text Then
• picNumber.Print nom, phoneNum
• Else
• picNumber.Print "Name not found."
• End If
• End Sub

Phone.txt
"Bert", "123-4567" "Ernie", "987-6543" "Grover",
"246-8321" "Oscar", "135-7900"
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Counters and Accumulators

• A Counter is a numeric variable that keeps track
  of the number of items that have been processed
  in the loop.
• An Accumulator is a numeric variable that totals
  numbers.

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Example of a Data File Analysis of Coins

• 1, 1, 5, 10, 10, 25
• (Two pennies, a nickel, two dimes and a quarter)

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Example Counter Accumulator

• Private Sub cmdAnalyze_Click()
• Dim numCoins As Integer, sum As Single, value
  As Single
• Open "COINS.TXT" For Input As 1
• numCoins 0
• sum 0
• Do While Not EOF(1)
• Input 1, value
• numCoins numCoins 1
• sum sum value
• Loop
• picValue.Print "The value of the" numCoins
  "coins is" sum "cents."
• Close 1
• End Sub

COINS.TXT

• 1, 1, 5, 10, 10, 25

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Output for the Previous Example

• The value of the 6 coins is 52 cents.

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Boolean Variables and Flags

• A Boolean variable can hold one of two values
  True or False.
• Initial (default) value is False.
• Flags are Boolean variables
• - Used within a loop to provide information that
  will be used after the loop terminates
• - Provide an alternative for terminating the loop
• Dim myFlag as Boolean

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Boolean Variables and Flags - Example

• Data file contains a list of words
• Determine whether or not the words are in order
• Determine the number of words in the file

WORDS.TXT
"cambist", "croissant", "deification" "hydrophyte"
, "incisor", "maculature" "macerate",
"narcolepsy", "shallon"
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Boolean Variables and Flags - Example

• Private Sub cmdAnalyze_Click()
• Dim orderFlag As Boolean, wordCounter As
  Integer
• Dim word1 As String, word2 As String
• 'Count words. Are they in alphabetical order?
• orderFlag True 'Assume words are in
  alphabetical order
• wordCounter 0
• word1 ""
• Open App.Path "\WORDS.TXT" For Input As 1
• Do While Not EOF(1)
• Input 1, word2
• wordCounter wordCounter 1
• If word1 gt word2 Then 'Two words are out
  of order
• orderFlag False
• End If
• word1 word2
• Loop
• Close 1

WORDS.TXT
"cambist", "croissant", "deification" "hydrophyte"
, "incisor", "maculature" "macerate",
"narcolepsy", "shallon"
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Another Example Multiple Phone Lists

• Data file contains a list of Phone Lists
• Each Phone List contains entries

LISTS.TXT
"CLIENTS.TXT" "FRIENDS.TXT" "KINFOLK.TXT"
FRIENDS.TXT
CLIENTS.TXT
KINFOLK.TXT
"Sam Cooper", "999-1231" "Millie Smith",
"555-1212" "Peter Jones", "414-3145"
"Mom", "346-8667" "Grandpa", "224-8873" "Uncle
Tom", "435-7574"
"George", "345-1235" "Virginia",
"673-8896" "Stuart", "245-5576" "Bert",
"123-4567" "Ernie", "987-6543" "Grover",
"246-8321" "Oscar", "135-7900"
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Boolean Variables and Flags - Example

• Private Sub cmdDisplay_Click()
• Dim foundFlag As Boolean, fileName As String
• Dim nom As String, phoneNum As String
• Open App.Path "\LISTS.TXT" For Input As 1
• foundFlag False
• nom ""
• Do While (foundFlag False) And (Not EOF(1))
• Input 1, fileName
• Open App.Path "\" fileName For Input As
  2
• Do While (nom ltgt txtName.Text) And (Not
  EOF(2))
• Input 2, nom, phoneNum
• Loop
• Close 2
• picNumber.Cls
• If nom txtName.Text Then
• picNumber.Print nom, phoneNum
• foundFlag True
• End If
• Loop

LISTS.TXT
"CLIENTS.TXT" "FRIENDS.TXT" "KINFOLK.TXT"
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Programming Assignment 6

• Write a program to do several types of analysis
  of the players of an athletic team.
  Specifically, the program should be able to do
  the following
• Determine the average age of the team members
• Determine the average GPA of the team members
• Determine the average weight of the team members
• Show all team members with a GPA that is above
  some level, which the user may enter
• The information about the team is stored in a
  single data file .

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Homework

• Page 280 1-13 Odd Problems
• 27 Turn in print-out of code

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For ... Next Loop

• Is used to create a counting loop.
• Loop control variable has an initial value.
• Loop control variable has a terminating value.
• Loop control variable has a Step value.