6c – Function Procedures
Lingma AchesonDepartment of Computer and Information Science, IUPUI
CSCI N331 VB .NET Programming
Function Procedures• Sometimes a procedure produces a
result, e.g. – CStr(intResult) will change the type of the
intResult value from an Integer type to a String type. The result is the value in the String format.
– Add(1, 2) will produce an addition result of 3.
• A procedure that generates a result is called a Function Procedure. A procedure that doesn’t generate a result is called a Sub Procedure.
• We can give the result to another variable.E.g.intResult = Add(intInput1, intInput2)
lblResult.Text = CStr(intResult)
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ProceduresSub Procedures:Button click event procedure: Create variables 1, 2 Take the user input and store in variable 1 and 2 ‘Tell the procedure what to add Add(variable1 and variable2)End of event procedure
Procedure Add(variable1 and variable2): Create variable 3 Add variable 1 to variable 2 and store in variable 3 display result in labelEnd of Add procedure
Can be changed to:Button click event procedure: Create variables 1, 2 Create variable 3 Take the user input and store in variable 1 and 2 variable 3 = Add(variable1 and variable 2) ‘use the result in this procedure display variable 3 in labelEnd of event procedure
Procedure Add(variable1 and variable2) Create variable 4 Add variable 1 to variable 2 and store in variable 4 pass the value of variable 4 outEnd of Add procedure
Function Procedures• Function - A type of procedure that produces a
result– Example:
Function procedure call and use the result:
dblResult = Add(dblInput1, dblInput2)
Function procedure definition: ‘”As Double” indicates that the function produces a
double value
Private Function Add(ByVal dblValue1 As Double, ByVal
dblValue2 As Double) As Double
Dim dblValue3 As Double
dblValue3 = dblValue1 + dblValue2
Return dblValue3
End Function– Return xxx: when the Function finishes execution, xxx is the
value to be passed out. Can be a value or a variable name.– Functions can also take parameters, just like Subs
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Function Procedures– E.g.
Private Sub btnCompute_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDisplay.Click
…‘Function Add takes two parameters, does the addition and
passes the ‘result out to the intAddResult.
intAddResult = Add(intFirst, intSecond) ‘Function call
txtAddResult.Text = CStr(intAddResult) End Sub
‘Function takes two integer parameters and returns an integer as the result
Private Function Add(ByVal intOne As Integer, ByVal intTwo As Integer) As Integer
Dim intResult As Integer = 0intResult= intOne + intTwoReturn intResult ‘pass the result out‘intResult is unnecessary. The above three lines can be
replaced by the ‘following line‘Return (intOne + intTwo)
End Function
Function Procedures– Each function can only return one value. E.g, In the following code, although there are two return
statements, only one return statement will be executed.
If (a condition is true) Then
return True ‘return a boolean value
Else
return False
End If
– Boolean data type revisit –
A boolean variable only has two values, True or False. It is often used to indicate a situation is true or false. E.g.
Dim blnPass As BooleanIf (intScore >=60) Then
blnPass = TrueElse blnPass = False