Public Class ComplexNumber
    Private m_RealPart As Single
    Private m_ImaginaryPart As Single

    ' Property procedures.
    Public Property RealPart() As Single
        Get
            Return m_RealPart
        End Get
        Set(ByVal Value As Single)
            m_RealPart = Value
        End Set
    End Property

    Public Property ImaginaryPart() As Single
        Get
            Return m_ImaginaryPart
        End Get
        Set(ByVal Value As Single)
            m_ImaginaryPart = Value
        End Set
    End Property

    ' Constructor using real and imaginary parts.
    Public Sub New(Optional ByVal real_part As Single = _
        0.0, Optional ByVal imaginary_part As Single = 0.0)
        m_RealPart = real_part
        m_ImaginaryPart = imaginary_part
    End Sub

    ' Constructor using a String of the form R + Ii.
    Public Sub New(ByVal string_value As String)
        Dim pos As Integer

        ' Remove spaces and the "i".
        string_value = string_value.Replace(" "c, "")
        string_value = string_value.ToLower.Replace("i"c, _
            "")

        ' Find the + or - between the parts.
        Dim plus_or_minus() As Char = {"+"c, "-"c}
        pos = string_value.IndexOfAny(plus_or_minus)
        If pos = 0 Then
            ' Skip the leading +/-.
            pos = string_value.IndexOfAny(plus_or_minus, 1)
        End If

        ' Get the real and imaginary parts.
        m_RealPart = Single.Parse(string_value.Substring(0, _
            pos))
        m_ImaginaryPart = _
            Single.Parse(string_value.Substring(pos))
    End Sub

    ' Return -Me.
    Public Function Negate() As ComplexNumber
        Return New ComplexNumber( _
            -m_RealPart, _
            -m_ImaginaryPart)
    End Function

    ' Return Me + complex_number.
    Public Function Plus(ByVal complex_number As _
        ComplexNumber) As ComplexNumber
        Return New ComplexNumber( _
            m_RealPart + complex_number.m_RealPart, _
            m_ImaginaryPart + _
                complex_number.m_ImaginaryPart)
    End Function

    ' Return Me - complex_number.
    Public Function Minus(ByVal complex_number As _
        ComplexNumber) As ComplexNumber
        Return Me.Plus(complex_number.Negate())
    End Function

    ' Return Me * complex_number.
    Public Function Times(ByVal complex_number As _
        ComplexNumber) As ComplexNumber
        Dim re_part As Single = _
            m_RealPart * complex_number.RealPart - _
            m_ImaginaryPart * complex_number.ImaginaryPart
        Dim im_part As Single = _
            m_RealPart * complex_number.ImaginaryPart + _
            m_ImaginaryPart * complex_number.RealPart

        Return New ComplexNumber(re_part, im_part)
    End Function

    ' Return a string representation of this number.
    Public Overrides Function ToString() As String
        ' Start with the real part.
        Dim result As String = m_RealPart.ToString()

        ' Add the imaginary part.
        If m_ImaginaryPart >= 0 Then
            result &= " + " & _
                m_ImaginaryPart.ToString() & _
                "i"
        Else
            result &= " - " & _
                (-m_ImaginaryPart).ToString() & _
                "i"
        End If

        Return result
    End Function
End Class