Solved: Appending two variables

Not quite sure what you are asking here....

This what you are looking for?

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
If TextBox2.Text <> "" Then
TextBox2.AppendText(" + " & TextBox1.Text)
Else
TextBox2.Text = TextBox1.Text
End If
End Sub

itcopt

ASKER

I tried your suggestion, I came up with (an example) 1+1+1+8+4

I need to display when one of the numeric buttons on the calculator is pressed, the value is appended to the label appearing at the top of the form. The calculator should display whatever is pressed in the label, such as

3+4-1+2/2 In the label

Then when I press the equal button the sum of the numbers is displayed.

Mike Tomlinson

Well the first part of your question is easy:

Public Class Form1
Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

Public Sub New()
MyBase.New()

'This call is required by the Windows Form Designer.
InitializeComponent()

'Add any initialization after the InitializeComponent() call

End Sub

'Form overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub

'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer

'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
Friend WithEvents Button1 As System.Windows.Forms.Button
Friend WithEvents Button2 As System.Windows.Forms.Button
Friend WithEvents Button3 As System.Windows.Forms.Button
Friend WithEvents Button4 As System.Windows.Forms.Button
Friend WithEvents Button5 As System.Windows.Forms.Button
Friend WithEvents Button6 As System.Windows.Forms.Button
Friend WithEvents Button7 As System.Windows.Forms.Button
Friend WithEvents Button8 As System.Windows.Forms.Button
Friend WithEvents Button9 As System.Windows.Forms.Button
Friend WithEvents Button17 As System.Windows.Forms.Button
Friend WithEvents Button18 As System.Windows.Forms.Button
Friend WithEvents Button11 As System.Windows.Forms.Button
Friend WithEvents Button12 As System.Windows.Forms.Button
Friend WithEvents Button13 As System.Windows.Forms.Button
Friend WithEvents Button14 As System.Windows.Forms.Button
Friend WithEvents Button10 As System.Windows.Forms.Button
Friend WithEvents Label1 As System.Windows.Forms.Label
Friend WithEvents Button19 As System.Windows.Forms.Button
Friend WithEvents Button15 As System.Windows.Forms.Button
Friend WithEvents Button16 As System.Windows.Forms.Button
<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
Me.Button1 = New System.Windows.Forms.Button
Me.Button2 = New System.Windows.Forms.Button
Me.Button3 = New System.Windows.Forms.Button
Me.Button4 = New System.Windows.Forms.Button
Me.Button5 = New System.Windows.Forms.Button
Me.Button6 = New System.Windows.Forms.Button
Me.Button7 = New System.Windows.Forms.Button
Me.Button8 = New System.Windows.Forms.Button
Me.Button9 = New System.Windows.Forms.Button
Me.Button17 = New System.Windows.Forms.Button
Me.Button18 = New System.Windows.Forms.Button
Me.Button11 = New System.Windows.Forms.Button
Me.Button12 = New System.Windows.Forms.Button
Me.Button13 = New System.Windows.Forms.Button
Me.Button14 = New System.Windows.Forms.Button
Me.Button10 = New System.Windows.Forms.Button
Me.Label1 = New System.Windows.Forms.Label
Me.Button19 = New System.Windows.Forms.Button
Me.Button15 = New System.Windows.Forms.Button
Me.Button16 = New System.Windows.Forms.Button
Me.SuspendLayout()
'
'Button1
'
Me.Button1.Location = New System.Drawing.Point(8, 40)
Me.Button1.Name = "Button1"
Me.Button1.Size = New System.Drawing.Size(32, 32)
Me.Button1.TabIndex = 0
Me.Button1.Text = "7"
'
'Button2
'
Me.Button2.Location = New System.Drawing.Point(48, 40)
Me.Button2.Name = "Button2"
Me.Button2.Size = New System.Drawing.Size(32, 32)
Me.Button2.TabIndex = 1
Me.Button2.Text = "8"
'
'Button3
'
Me.Button3.Location = New System.Drawing.Point(88, 40)
Me.Button3.Name = "Button3"
Me.Button3.Size = New System.Drawing.Size(32, 32)
Me.Button3.TabIndex = 2
Me.Button3.Text = "9"
'
'Button4
'
Me.Button4.Location = New System.Drawing.Point(8, 80)
Me.Button4.Name = "Button4"
Me.Button4.Size = New System.Drawing.Size(32, 32)
Me.Button4.TabIndex = 3
Me.Button4.Text = "4"
'
'Button5
'
Me.Button5.Location = New System.Drawing.Point(48, 80)
Me.Button5.Name = "Button5"
Me.Button5.Size = New System.Drawing.Size(32, 32)
Me.Button5.TabIndex = 4
Me.Button5.Text = "5"
'
'Button6
'
Me.Button6.Location = New System.Drawing.Point(88, 80)
Me.Button6.Name = "Button6"
Me.Button6.Size = New System.Drawing.Size(32, 32)
Me.Button6.TabIndex = 5
Me.Button6.Text = "6"
'
'Button7
'
Me.Button7.Location = New System.Drawing.Point(8, 120)
Me.Button7.Name = "Button7"
Me.Button7.Size = New System.Drawing.Size(32, 32)
Me.Button7.TabIndex = 6
Me.Button7.Text = "1"
'
'Button8
'
Me.Button8.Location = New System.Drawing.Point(48, 120)
Me.Button8.Name = "Button8"
Me.Button8.Size = New System.Drawing.Size(32, 32)
Me.Button8.TabIndex = 7
Me.Button8.Text = "2"
'
'Button9
'
Me.Button9.Location = New System.Drawing.Point(88, 120)
Me.Button9.Name = "Button9"
Me.Button9.Size = New System.Drawing.Size(32, 32)
Me.Button9.TabIndex = 8
Me.Button9.Text = "3"
'
'Button17
'
Me.Button17.Location = New System.Drawing.Point(8, 200)
Me.Button17.Name = "Button17"
Me.Button17.Size = New System.Drawing.Size(32, 32)
Me.Button17.TabIndex = 9
Me.Button17.Text = "C"
'
'Button18
'
Me.Button18.Location = New System.Drawing.Point(48, 200)
Me.Button18.Name = "Button18"
Me.Button18.Size = New System.Drawing.Size(32, 32)
Me.Button18.TabIndex = 10
Me.Button18.Text = "CE"
'
'Button11
'
Me.Button11.Location = New System.Drawing.Point(128, 40)
Me.Button11.Name = "Button11"
Me.Button11.Size = New System.Drawing.Size(32, 32)
Me.Button11.TabIndex = 11
Me.Button11.Text = "/"
'
'Button12
'
Me.Button12.Location = New System.Drawing.Point(128, 80)
Me.Button12.Name = "Button12"
Me.Button12.Size = New System.Drawing.Size(32, 32)
Me.Button12.TabIndex = 12
Me.Button12.Text = "X"
'
'Button13
'
Me.Button13.Location = New System.Drawing.Point(128, 120)
Me.Button13.Name = "Button13"
Me.Button13.Size = New System.Drawing.Size(32, 32)
Me.Button13.TabIndex = 13
Me.Button13.Text = "-"
'
'Button14
'
Me.Button14.Location = New System.Drawing.Point(128, 160)
Me.Button14.Name = "Button14"
Me.Button14.Size = New System.Drawing.Size(32, 32)
Me.Button14.TabIndex = 14
Me.Button14.Text = "+"
'
'Button10
'
Me.Button10.Location = New System.Drawing.Point(48, 160)
Me.Button10.Name = "Button10"
Me.Button10.Size = New System.Drawing.Size(32, 32)
Me.Button10.TabIndex = 15
Me.Button10.Text = "0"
'
'Label1
'
Me.Label1.Anchor = CType(((System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Left) _
Or System.Windows.Forms.AnchorStyles.Right), System.Windows.Forms.AnchorStyles)
Me.Label1.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle
Me.Label1.Location = New System.Drawing.Point(8, 8)
Me.Label1.Name = "Label1"
Me.Label1.Size = New System.Drawing.Size(152, 24)
Me.Label1.TabIndex = 16
Me.Label1.TextAlign = System.Drawing.ContentAlignment.MiddleRight
'
'Button19
'
Me.Button19.Location = New System.Drawing.Point(88, 200)
Me.Button19.Name = "Button19"
Me.Button19.Size = New System.Drawing.Size(72, 32)
Me.Button19.TabIndex = 19
Me.Button19.Text = "="
'
'Button15
'
Me.Button15.Location = New System.Drawing.Point(8, 160)
Me.Button15.Name = "Button15"
Me.Button15.Size = New System.Drawing.Size(32, 32)
Me.Button15.TabIndex = 20
Me.Button15.Text = "("
'
'Button16
'
Me.Button16.Location = New System.Drawing.Point(88, 160)
Me.Button16.Name = "Button16"
Me.Button16.Size = New System.Drawing.Size(32, 32)
Me.Button16.TabIndex = 21
Me.Button16.Text = ")"
'
'Form1
'
Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
Me.ClientSize = New System.Drawing.Size(168, 238)
Me.Controls.Add(Me.Button16)
Me.Controls.Add(Me.Button15)
Me.Controls.Add(Me.Button19)
Me.Controls.Add(Me.Label1)
Me.Controls.Add(Me.Button10)
Me.Controls.Add(Me.Button14)
Me.Controls.Add(Me.Button13)
Me.Controls.Add(Me.Button12)
Me.Controls.Add(Me.Button11)
Me.Controls.Add(Me.Button18)
Me.Controls.Add(Me.Button17)
Me.Controls.Add(Me.Button9)
Me.Controls.Add(Me.Button8)
Me.Controls.Add(Me.Button7)
Me.Controls.Add(Me.Button6)
Me.Controls.Add(Me.Button5)
Me.Controls.Add(Me.Button4)
Me.Controls.Add(Me.Button3)
Me.Controls.Add(Me.Button2)
Me.Controls.Add(Me.Button1)
Me.Name = "Form1"
Me.Text = "Calculator"
Me.ResumeLayout(False)

End Sub

#End Region

Private Sub Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles Button1.Click, Button2.Click, Button3.Click, Button4.Click, _
Button5.Click, Button6.Click, Button7.Click, Button8.Click, Button9.Click, _
Button10.Click, Button11.Click, Button12.Click, Button13.Click, Button14.Click, _
Button15.Click, Button16.Click, Button17.Click, Button18.Click

Select Case sender.text
Case "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "(", ")"
Label1.Text = Label1.Text & sender.text

Case "/", "X", "-", "+"
If Not (Label1.Text.EndsWith("/") Or Label1.Text.EndsWith("X") Or _
Label1.Text.EndsWith("-") Or Label1.Text.EndsWith("+") Or _
(Label1.Text.Length = 0)) Then
Label1.Text = Label1.Text & sender.text
End If

Case "C"
Label1.Text = ""

Case "CE"
If Label1.Text.Length > 0 Then
Label1.Text = Label1.Text.Substring(0, Label1.Text.Length - 1)
End If

Case "="
' parse the expression...

End Select

End Sub

End Class

Mike Tomlinson

The second part of your question is not so easy. What you are asking for is an expression evaluator:

3+4-1+2/2

Their are many things involved in doing this calculation. You first need to define your operator precedence. Is it simply left to right, or should multiplication and division be done before addition and subtraction? Will you allow grouping with parentheses?

~IM

Mike Tomlinson

Here is a website that explains how to convert expressions from infix to postfix, and how to evaluate postfix (reverse polish notation or RPN) expressions:
http://www.spsu.edu/cs/faculty/bbrown/web_lectures/postfix/

Writing the code for this is not a 50 point question.

This is a common homework assignment in college courses. If this is homework, what progress have you made so far? (Apologies if this is not homework.)

~IM

itcopt

ASKER

The first part you gave worked great, Thanks!

This is homework, and this is what I have for the equal button: (txtDisplay2.text is a running tape on the side of the calc.) Right now I am testing the subtraction button, the program dies on line result = CDbl(num1) - CDbl(num2) ) but I thought that the next line txtDisplay.Text = CStr(result) would change the double result "6-3" to type string ???

This is homework, and this is what I have for the equal button:

Private Sub btnEquals_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnEquals.Click
num1 = txtDisplay.Text
'num2 = txtDisplay2.Text

If Len(txtDisplay.Text) > 0 Then
Select Case symbol
Case "+"

result = CDbl(num1) + CDbl(num2)
txtDisplay.Text = CStr(result)
'txtDisplay2.Text = CStr(result)

Case "-"

result = CDbl(num1) - CDbl(num2) ****program dies on this line ** right now I'm only testing the subtraction button
txtDisplay.Text = CStr(result)

Case "X"

result = CDbl(num1) * CDbl(num2)
txtDisplay.Text = CStr(result)
Case "\"

If num2 <> 0 Then

result = CDbl(num1) / CDbl(num2)
txtDisplay.Text = CStr(result)
Else
MsgBox("Divide Error")
End If
End Select

Else
MsgBox("Not enough Arguments!")
End If

End Sub

Then for the subtraction button I have:

Private Sub btnSub_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSub.Click

symbol = "-"
num1 = txtDisplay.Text

End Sub

Mike Tomlinson

You have commented out the num2 line so it doesn't have a value. This is probably why it bombs when you try to convert it to a double using CDbl().

Where is symbol coming from in the Select Case statement?

Are you going to evaluate complex expressions like the ones you posted?

3+4-1+2/2
<or>
1+1+1+8+4

Or are you only going to have two values and one operator in each expression?

~IM

itcopt

ASKER

I had taken out the commented line and still got the same error ??
The calculator should be able to do complex expressions 3+4-1+2/2

The symbol is coming from the btn click event: This is for the subtraction symbol:

Private Sub btnSub_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSub.Click

symbol = "-"
num1 = txtDisplay.Text

End Sub

Also I declared the num1 and num2 as Object, should this be integer?

Thanks!

Mike Tomlinson

num1 and num2 should be Strings since you are assigning the .Text property to them. Result should be a Double since you are using CDbl().

The main problem though, is that your approach won't be able to handle complex expressions since symbol is only going to have the last operation clicked but you may have more than one operation in your expressions. You can't compute the answer as it is entered since multiplication and division should be done before addition and subtraction. You must wait until the entire expression is entered and then parse it.

The correct way to do it is to use the techniques outlined in the link I provided you earlier.

Is the user supposed to enter the whole expression at once or is it supposed to work like a normal calculator?

5+1=6

would be:

5 (5 in display)
+ (5 in display)
1 (1 in display)
= (6 in display)

Sorry if I have misunderstood the requirements...

~IM

itcopt

ASKER

The requirements call for 5+1-2 in txtDisplay.text (not like a normal calc)
press equal button to force out last calculation
result displayed in txtDisplay2.text as
5+
1+
6
2-
4

txtDisplay2.text is acting as a running tape.

Mike Tomlinson

Ah! ok...it's clear to me now. It's a new fangled hybrid calculator. ;)