Modify a text file: $/0924-tip.vb

$/0924-tip.vb

Public Class Form1

'******** I/O METHODS *******
    Sub say(ByVal s As String)
        '**** Output a string to the listbox.
        Me.output.Items.Add(s)    'Display the string s in listbox.
    End Sub
    Sub saywhat(ByVal s As String, ByVal r As Double)
        '**** Output a string and a value to the listbox.
        Me.output.Items.Add(s & " " & Format(r))    'Display string s & r in listbox.
    End Sub
    Sub saymsg(ByVal what As String, ByVal r As Double)
        '**** Output a string and a value to the listbox.
        Dim s As String
        s = "The " & what & " is "
        Me.output.Items.Add(s & " " & Format(r))    'Display string s & r in listbox.
    End Sub

Function getFirst() As Double
        'Return the first value from form (textbox)
        Dim result As Double
        result = CDbl(Me.txtFirst.Text)
        Return result
    End Function
    Function getSecond() As Double
        'Return the second value from form (textbox)
        Return CDbl(Me.txtSecond.Text)
    End Function

'****** Math methods *****
    Function diff(ByVal a As Double, ByVal b As Double) As Double
        'Return the difference between a and b
        Dim result As Double
        result = a - b
        Return result
    End Function
    Function sum(ByVal a As Double, ByVal b As Double) As Double
        'Return the sum of a and b
        Dim result As Double

result = a + b

Return result
    End Function

Private Sub btnDiv_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDiv.Click
        '****** Divide, but check for div by zero.  Output result (or err msg).

Dim a, b As Double         ' First and second inputs (from txtFirst, txtSecond)
        Dim result As Double       ' Result of operation.
        Dim msg As String           'The output string will be composed here.
        Dim what As String = "quotient"     'Result type.

'1. INPUT:  Get a, b
        a = CDbl(Me.txtFirst.Text)
        b = CDbl(Me.txtSecond.Text)

'2. PROCESS:  Compute the quotient, but first check for /0
        If (b <> 0) Then
            result = a / b
            '--     msg = "The quotient is " & Format(result)
            msg = "The " & what & " is " & Format(result)
        Else
            msg = "!!!! Denominator cannot be zero!"
        End If

'3. OUTPUT:  Show the answer.
        say(msg)
    End Sub

Private Sub btnMul_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMul.Click
        '****** Multiply 2 #s.  Output result (or err msg).

Dim a, b As Double         ' First and second inputs (from txtFirst, txtSecond)
        Dim result As Double       ' Result of operation.
        Dim msg As String
        Dim what As String = "product"

'0. INIT:
        msg = "The " & what & " is "

'1. INPUT:  Get a, b
        a = CDbl(Me.txtFirst.Text)
        b = CDbl(Me.txtSecond.Text)

'2. PROCESS:  Compute the quotient, but first check for /0
        result = a * b

'3. OUTPUT:  Show the answer.
        saywhat(msg, result)
    End Sub

Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click
        '****** Add 2 #s.  Output result.

Dim a, b As Double         ' First and second inputs (from txtFirst, txtSecond)
        Dim x As Double       ' Result of operation.
        Dim what As String = "sum"

'1. INPUT:  a, b
        a = getFirst()
        b = getSecond()

'2. PROCESS:  Add a, b
        x = sum(a, b)

'3. OUTPUT:  Show the answer.
        saymsg(what, x)

End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        '****** Subtract 2 #s.  Output result.
        Dim a, b As Double         ' First and second inputs (from txtFirst, txtSecond)
        Dim x As Double       ' Result of operation.
        Dim what As String = "difference"

'1. INPUT:  a, b
        a = getFirst()
        b = getSecond()

'2. PROCESS:  Add a, b
        x = diff(a, b)

'3. OUTPUT:  Show the answer.
        saymsg(what, x)

End Sub

End Class