Lecture 7 Processing with Array

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					Lecture 7: Processing with Array


           Daniel Chen
        Processing with Arrays
•   Often use For-Next Loop
•   Sum and Average
•   Largest number
•   Smallest number
•   Find a given number
•   Sort an Array
                Average
intSum = 0
 For intCounter= 0 to intNumValues-1
  intSum = intSum + intA(intCounter)
 Next
sngAvg=intSum / intNumValues
Example (SumAvg)
                Find Largest
Begin procedure
  Set largest value to first item in list
  Repeat beginning with second item to largest item
      if item in list> largest value then
             largest value=item in list
      end decision
  End Repeat
  Display largest value
End procedure
Practice
        Find Smallest
(What will be the pseudo code?)
         Find Smallest
 (What will be the pseudo code?)
Begin Procedure
  Set smallest value to first item in list
  Repeat beginning with second item to largest item
       if item in list< smallest value then
               smallest value=item in list
       end decision
  End Repeat
  Display smallest value
End Procedure
Example
      Multiple Aligned Arrays
• Arrays are homogeneous
  – All the data in AN array is of the same type
• When you have heterogeneous data, you
  often need more than one array
  – An integer array for Score
  – A currency array for salary
  – A string array for Name
     Example (Find a number)
• Input data from a file including name and
  number (no duplicated numbers)
• Read the arrays during Form_Load
  – Note use of quotation marks
  – Need to have no extra returns
  – Remember to Close
• Load the list box during Form_Load
                    Pseudo Code
Begin procedure to find a number
Input a NumberToFind
Set Flag to False
Repeat for each number in number list
    if NumberToFind = a number in number list then
         Flag=True
         Save index of the number in number list
    end decision
End repeat
If Flag=True then
    use saved index to display information related to that number
Else
    display information that number not on the list
End decision
End Procedure
         The MsgBox Function
• We’ve used MsgBox as a Sub
      • It didn’t have a value
• Now we use it as a function
   intVariable=MsgBox(message, buttons, title)
• Unlike the InputBox, you don’t get input
• You do get find out what button was clicked
• And, of course, to choose which buttons are used
   – It returns an integer which matches up against some
     already defined vb-names (see page 234; Table 6-3)
     Example: Get the number
• Based on Find a Number
• Click a name in the listbox to get his/her
  number
    A new property of List Box
• The ListIndex property tells which line is
  clicked
     • It’s –1 if nothing is clicked
     • If you set it to-1, it unclicks
• The listbox is numbered the same way as
  the two arrays
       Tips on Array Processing
• Because arrays are often used throughout a problem, it is
  often true that their Dim statement be at the form-level
• Dim an array large enough, though you may (often) use
  less than you allocated
• It is also common that the “used” size of the array is stored
  in a variable Dim-ed at the form-level
• Form_Load is a good place to read in arrays
• String values are best contained in quotation marks in a file
   – To take care of the blanks in a string
            Multiple Forms
• Menu
  – Project->Add Form [probably new]
• formname.Hide
• formname.Show
  – These are methods
             Searching in Strings

* Searching for strings using a loop requires that you use
   UCase() or LCase() to convert all strings to the same case.
* To search for a sub-string within a string, you use the lnStr
   function:
  Instr (string to search, search string)
For example, InStr(“Go Dogs”, “D “) returns 4 because “D” is in
  the 4th position. If the character does not exist, InStr()
  returns a zero.
*NOTE: InStr() is case sensitive!!!
                 Quiz
• Instr(“Thompson”, “mp”)
  – Equals ?
• InStr(“Thompson”, “MP”)
  – Equals ?
• InStr(Ucase(“Thompson”),Ucase(“MP”))
  – Equals ?
                 Quiz
• Instr(“Thompson”, “mp”)
  – Equals 4
• InStr(“Thompson”, “MP”)
  – Equals 0
• InStr(Ucase(“Thompson”),Ucase(“MP”))
  – Equals 4
     Example (Get the Name)
• To find a near match on name
• Report the number for that name
      Two-Dimensional Arrays
• When you are working with a table instead of a
  list, you have a 2-dimensional array.
• 2-D arrays use two subscripts with the first
  subscript referring to the row value and the second
  subscript referring to the column value.
• Nested For-next loops are often used to work with
  2-D arrays with the inner loop matching the
  columns and the outer loop matching the rows.
 Using the Step Commands for
          Debugging


     Step into
                                                      Stepout of
                 The Step Commands
                                          Step Over


If you select Step Into, you can “step” through the
code, line by line and note the result of the code in the
various windows--Watch, Locals, or Immediate.

				
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