Public Class Form1
    Class Complex
        Public R As Double, I As Double, EPS As Double
        Public Sub New(R As Double, I As Double, EPS As Double)
            Me.R = R : Me.I = I : Me.EPS = EPS
        End Sub
        Public Sub New(R As Double, I As Double)
            Me.R = R : Me.I = I : Me.EPS = 0.000001
        End Sub
        Public Sub New(R As Double)
            Me.R = R : Me.I = 0 : Me.EPS = 0.000001
        End Sub
        Public Function minusCom() As Complex
            Return New Complex(-Me.R, -Me.I, Me.EPS)
        End Function
        Public Function addDbl(R As Double) As Complex
            Return New Complex(Me.R + R, Me.I, Me.EPS)
        End Function
        Public Function subDbl(R As Double) As Complex
            Return New Complex(Me.R - R, Me.I, Me.EPS)
        End Function
        Public Function mulDbl(R As Double) As Complex
            Return New Complex(Me.R * R, Me.I * R, Me.EPS)
        End Function
        Public Function divDbl(R As Double) As Complex
            If Math.Abs(R) < Me.EPS Then
                MsgBox("逆数で0割りが起こりました")
                Return New Complex(0, 0)
            Else
                Return New Complex(Me.R / R, Me.I / R, Me.EPS)
            End If
        End Function
        Public Function Abs() As Double
            Return Math.Sqrt(Me.R * Me.R + Me.I * Me.I)
        End Function
        Public Function inv() As Complex
            Dim ImageP As Double, RealP As Double, S As Double
            ImageP = Me.I : RealP = Me.R
            If Math.Abs(ImageP) < Me.EPS Then
                If Math.Abs(RealP) < Me.EPS Then
                    MsgBox("逆数で0割りが起こりました")
                    Return New Complex(0, 0)
                Else
                    Return New Complex(1 / RealP, 0)
                End If
            Else
                S = RealP * RealP + ImageP * ImageP
                If Math.Abs(S) < Me.EPS Then
                    MsgBox("逆数で0割りが起こりました")
                    Return New Complex(0, 0)
                Else
                    Return New Complex(RealP / S, -ImageP / S)
                End If
            End If
        End Function
        Public Overrides Function ToString() As String
            Dim S As Double, SS As Double
            Dim K As String
            S = Me.I : SS = Me.R

            If Math.Abs(S) < 0.000005 And Math.Abs(SS) < 0.000005 Then
                Return "0.0000"
            ElseIf Math.Abs(S) < 0.000005 Then
                Return Format(Me.R, "#0.0000")
            ElseIf Math.Abs(SS) < 0.000005 Then
                Return Format(S, "#0.0000") & "*j"
            Else
                K = " - "
                If S > 0 Then K = " + "
                S = Math.Abs(S)
                Return Format(SS, "#0.0000") & K & Format(S, "#0.0000") & "*j"
            End If
        End Function
        Public Function Sqrt() As Complex
            Dim SS As Double
            SS = Math.Sqrt(Me.R * Me.R + Me.I * Me.I)
            Return New Complex(Math.Sqrt((SS + Me.R) / 2), Math.Sqrt((SS - Me.R) / 2))
        End Function
        Public Function Exp() As Complex
            Dim EP As Double, TH As Double
            EP = Math.Exp(Me.R) : TH = Me.I
            Return New Complex(Math.Cos(TH) * EP, Math.Sin(TH) * EP)
        End Function

        Public Overrides Function Equals(obj As Object) As Boolean
            Return MyBase.Equals(obj)
        End Function
        Public Overrides Function GetHashCode() As Integer
            Return MyBase.GetHashCode()
        End Function

        Public Shared Operator +(ByVal a As Complex, ByVal b As Complex) As Complex
            Return New Complex(a.R + b.R, a.I + b.I)
        End Operator
        Public Shared Operator -(ByVal a As Complex, ByVal b As Complex) As Complex
            Return New Complex(a.R - b.R, a.I - b.I)
        End Operator
        Public Shared Operator *(ByVal a As Complex, ByVal b As Complex) As Complex
            Return New Complex(a.R * b.R - a.I * b.I, a.R * b.I + a.I * b.R)
        End Operator
        Public Shared Operator /(ByVal a As Complex, ByVal b As Complex) As Complex
            Return a * b.inv()
        End Operator
        Public Shared Operator ^(ByVal X As Complex, ByVal N As Integer) As Complex
            Dim P As Complex = New Complex(1, 0)
            Dim abN As Integer = Math.Abs(N)
            Do While abN > 0
                If (abN Mod 1) Then P = P * X
                abN = abN / 2 : X = X * X
            Loop
            If N < 0 Then
                Return P.inv()
            Else
                Return P
            End If
        End Operator
    End Class
    Public C1 As Complex, C2 As Complex, CR As Complex

    Public Function setImage(I As Double) As Complex
        Return New Complex(0, I)
    End Function
    Public Function strCom(A As Complex) As String
        Dim S As Double, SS As Double
        Dim K As String
        S = A.I : SS = A.R

        If Math.Abs(S) < 0.000005 And Math.Abs(SS) < 0.000005 Then
            strCom = "0.0000"
        ElseIf Math.Abs(S) < 0.000005 Then
            strCom = Format(A.R, "#0.0000")
        ElseIf Math.Abs(SS) < 0.000005 Then
            strCom = Format(S, "#0.0000") & "*j"
        Else
            K = " - "
            If S > 0 Then K = " + "
            S = Math.Abs(S)
            strCom = Format(A.R, "#0.0000") & K & Format(S, "#0.0000") & "*j"
        End If
    End Function
    Private Sub setData()
        Dim R1 As Double, I1 As Double, R2 As Double, I2 As Double
        R1 = Val(TextBox1.Text) : I1 = Val(TextBox2.Text) : C1 = New Complex(R1, I1)
        R2 = Val(TextBox3.Text) : I2 = Val(TextBox4.Text) : C2 = New Complex(R2, I2)
    End Sub
    Private Sub setResult()
        TextBox5.Text = CR.R : TextBox6.Text = CR.I
    End Sub
    Private Sub Comp()
        Dim S As String = ComboBox1.SelectedItem
        Select Case S
            Case "+" : CR = C1 + C2
            Case "-" : CR = C1 - C2
            Case "*" : CR = C1 * C2
            Case "/" : CR = C1 / C2
            Case "+$" : CR = C1.addDbl(C2.R)
            Case "-$" : CR = C1.subDbl(C2.R)
            Case "*$" : CR = C1.mulDbl(C2.R)
            Case "/$" : CR = C1.divDbl(C2.R)
            Case "Abs" : CR = New Complex(C1.Abs())
            Case Else : CR = New Complex(0, 0)
        End Select
    End Sub
    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        setData()
        Comp()
        setResult()
    End Sub

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        ComboBox1.Items.Add("+")
        ComboBox1.Items.Add("-")
        ComboBox1.Items.Add("*")
        ComboBox1.Items.Add("/")
        ComboBox1.Items.Add("+$")
        ComboBox1.Items.Add("-$")
        ComboBox1.Items.Add("*$")
        ComboBox1.Items.Add("/$")
        ComboBox1.Items.Add("Abs")
    End Sub
End Class