Binary Search Tree - CompareTo Error

28 Dec 2006 1:38 PM

BenCoo

Hello,

In a Binary Search Tree I get the error : Object must be of type String

if I run the form only with the   "Dim bstLidnummer As New BinarySearchTree"
it works fine.

Thanks for any help on this,

Benny

My BST-code lookes lokes this :
**************************************************
Class BST
**************************************************
Public Class BinarySearchTree
   Private Class TreeNode
      Private mData As IComparable
      Private mLeftNode As TreeNode
      Private mRightNode As TreeNode

      Public Sub New(ByVal data As IComparable)
         Me.mData = data
      End Sub

      Public ReadOnly Property Data() As IComparable
         Get
            Return Me.mData
         End Get
      End Property

      Public Property LeftNode() As TreeNode
         Get
            Return Me.mLeftNode
         End Get
         Set(ByVal value As TreeNode)
            Me.mLeftNode = value
         End Set
      End Property

      Public Property RightNode() As TreeNode
         Get
            Return Me.mRightNode
         End Get
         Set(ByVal value As TreeNode)
            Me.mRightNode = value
         End Set
      End Property

      Public Sub Add(ByVal data As IComparable)
         If data.CompareTo(Me.mData) <= 0 Then
            If Me.mLeftNode Is Nothing Then
               Me.mLeftNode = New TreeNode(data)
            Else
               Me.mLeftNode.Add(data)
            End If
         Else
            If Me.mRightNode Is Nothing Then
               Me.mRightNode = New TreeNode(data)
            Else
               Me.mRightNode.Add(data)
            End If
         End If
      End Sub
   End Class

   Private mRoot As TreeNode

   Public Sub Add(ByVal data As IComparable)
      If mRoot Is Nothing Then
         mRoot = New TreeNode(data)
      Else
         mRoot.Add(data)
      End If
   End Sub

   Public Function Search(ByVal data As IComparable) As Object
      Return Me.Search(data, Me.mRoot)
   End Function

   Private Function Search(ByVal data As IComparable, ByVal node As
TreeNode) As Object

      If node Is Nothing Then
         Return Nothing
      Else
         Dim result As Integer = data.CompareTo(node.Data) '****** this is
the error I get on this line :Object must be of type String.

         If result = 0 Then
            Return node.Data
         ElseIf result < 0 Then
            Return Me.Search(data, node.LeftNode)
         Else
            Return Me.Search(data, node.RightNode)
         End If
      End If

   End Function
End Class
*****************************
The class Person
*****************************
Public Class Persoon
   Inherits BusinessObject
   Implements IComparable

   Private mVnaam As String
   Private mAnaam As String

   Public Sub New(ByVal Vnaam As String, ByVal Anaam As String)
      Me.mVnaam = Vnaam
      Me.mAnaam = Anaam
   End Sub

   Public Property Vnaam() As String
      Get
         Return Me.mVnaam
      End Get
      Set(ByVal value As String)
         mVnaam = value
      End Set
   End Property

   Public Property Anaam() As String
      Get
         Return Me.mAnaam
      End Get
      Set(ByVal value As String)
         Me.mAnaam = value
      End Set
   End Property

   Public Overrides Function IsValid() As Boolean
      If Me.isValidVnaam() And Me.isValidAnaam() Then
         Return True
      Else
         Return False
      End If
   End Function

   Private Function isValidVnaam() As Boolean
      If Me.Vnaam.Trim.Length > 0 Then
         Return True
      Else
         Return False
      End If
   End Function

   Private Function isValidAnaam() As Boolean
      If Me.Anaam.Trim.Length > 0 Then
         Return True
      Else
         Return False
      End If
   End Function

   Public Overloads Function CompareTo(ByVal obj As Object) As Integer
Implements System.IComparable.CompareTo
      Return Me.mVnaam.CompareTo(CType(obj, Persoon).Vnaam)
   End Function
End Class
**********************************
The Form :
**********************************
Public Class frmBinarySearchTree

   Private Sub btnExecute_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles btnExecute.Click
      Dim bstLedenLijst As New BinarySearchTree
      Dim bstLidnummer As New BinarySearchTree
      Dim txtOutput As String = ""

      bstLidnummer.Add("5")
      bstLidnummer.Add("2")
      bstLidnummer.Add("1")
      bstLidnummer.Add("4")
      bstLidnummer.Add("3")
      txtOutput = bstLidnummer.Search("3") & vbCrLf

      bstLedenLijst.Add(New Persoon("Nicole", "Kidman"))
      bstLedenLijst.Add(New Persoon("Jamie-Lee", "Curtis"))
      bstLedenLijst.Add(New Persoon("Demi", "Moore"))
      bstLedenLijst.Add(New Persoon("Julia", "Roberts"))
      bstLedenLijst.Add(New Persoon("Andie", "MacDowell"))

      txtOutput &= bstLedenLijst.Search("Demi") ' & vbCrLf

      Me.txtOutput.Text = txtOutput

   End Sub

   Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles btnExit.Click
      Application.Exit()
   End Sub

End Class

28 Dec 2006 2:02 PM

Jay B. Harlow

BenCoo,
Interesting homework assignment; I miss those days...

Anyway to answer your question:

>      Dim bstLedenLijst As New BinarySearchTree
>      Dim bstLidnummer As New BinarySearchTree
>      Dim txtOutput As String = ""
>
>      bstLidnummer.Add("5")
>      txtOutput = bstLidnummer.Search("3") & vbCrLf
>
>      bstLedenLijst.Add(New Persoon("Nicole", "Kidman"))
>
>      txtOutput &= bstLedenLijst.Search("Demi") ' & vbCrLf

Ah! There's the Rub!

bstLedenLijst contains a collection of Persoon objects, you are attempting
to compare Persoon objects to a String object! You need to pass a Persoon
object to bstLedenLijst.Search. I would recommend you change
BinarySearchTree to a Generic class; changing this obscure runtime error
into an obvious compile time error!

Something like:

Public Class BinarySearchTree(Of T As IComparable)

    Private Class TreeNode
        Private mData As T
        Private mLeftNode As TreeNode
        Private mRightNode As TreeNode

        Public Sub New(ByVal data As T)
            Me.mData = data
        End Sub

        Public ReadOnly Property Data() As T
            Get
                Return Me.mData
            End Get
        End Property

        Public Property LeftNode() As TreeNode
            Get
                Return Me.mLeftNode
            End Get
            Set(ByVal value As TreeNode)
                Me.mLeftNode = value
            End Set
        End Property

        Public Property RightNode() As TreeNode
            Get
                Return Me.mRightNode
            End Get
            Set(ByVal value As TreeNode)
                Me.mRightNode = value
            End Set
        End Property

        Public Sub Add(ByVal data As T)
            If data.CompareTo(Me.mData) <= 0 Then
                If Me.mLeftNode Is Nothing Then
                    Me.mLeftNode = New TreeNode(data)
                Else
                    Me.mLeftNode.Add(data)
                End If
            Else
                If Me.mRightNode Is Nothing Then
                    Me.mRightNode = New TreeNode(data)
                Else
                    Me.mRightNode.Add(data)
                End If
            End If
        End Sub
    End Class

    Private mRoot As TreeNode

    Public Sub Add(ByVal data As T)
        If mRoot Is Nothing Then
            mRoot = New TreeNode(data)
        Else
            mRoot.Add(data)
        End If
    End Sub

    Public Function Search(ByVal data As T) As Object
        Return Me.Search(data, Me.mRoot)
    End Function

    Private Function Search(ByVal data As T, ByVal node As TreeNode) As
Object

        If node Is Nothing Then
            Return Nothing
        Else
            Dim result As Integer = data.CompareTo(node.Data) '****** this
is the error I get on this line :Object must be of type String.

            If result = 0 Then
                Return node.Data
            ElseIf result < 0 Then
                Return Me.Search(data, node.LeftNode)
            Else
                Return Me.Search(data, node.RightNode)
            End If
        End If

    End Function
End Class

Then when you define your trees, you give the type of tree they are!

> Dim bstLedenLijst As New BinarySearchTree(Of String)
> Dim bstLidnummer As New BinarySearchTree(Of Persoon)

NOTE: You need VS 2005 for generics.

--
Hope this helps
Jay B. Harlow
..NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net

Show quoteHide quote

"BenCoo" <teddy***@hotmail.com> wrote in message
news:CNPkh.260824$tk1.5394486@phobos.telenet-ops.be...
> Hello,
>
> In a Binary Search Tree I get the error : Object must be of type String
>
> if I run the form only with the   "Dim bstLidnummer As New
> BinarySearchTree"
> it works fine.
>
> Thanks for any help on this,
>
> Benny
>
> My BST-code lookes lokes this :
> **************************************************
> Class BST
> **************************************************
> Public Class BinarySearchTree
>   Private Class TreeNode
>      Private mData As IComparable
>      Private mLeftNode As TreeNode
>      Private mRightNode As TreeNode
>
>      Public Sub New(ByVal data As IComparable)
>         Me.mData = data
>      End Sub
>
>      Public ReadOnly Property Data() As IComparable
>         Get
>            Return Me.mData
>         End Get
>      End Property
>
>      Public Property LeftNode() As TreeNode
>         Get
>            Return Me.mLeftNode
>         End Get
>         Set(ByVal value As TreeNode)
>            Me.mLeftNode = value
>         End Set
>      End Property
>
>      Public Property RightNode() As TreeNode
>         Get
>            Return Me.mRightNode
>         End Get
>         Set(ByVal value As TreeNode)
>            Me.mRightNode = value
>         End Set
>      End Property
>
>      Public Sub Add(ByVal data As IComparable)
>         If data.CompareTo(Me.mData) <= 0 Then
>            If Me.mLeftNode Is Nothing Then
>               Me.mLeftNode = New TreeNode(data)
>            Else
>               Me.mLeftNode.Add(data)
>            End If
>         Else
>            If Me.mRightNode Is Nothing Then
>               Me.mRightNode = New TreeNode(data)
>            Else
>               Me.mRightNode.Add(data)
>            End If
>         End If
>      End Sub
>   End Class
>
>   Private mRoot As TreeNode
>
>   Public Sub Add(ByVal data As IComparable)
>      If mRoot Is Nothing Then
>         mRoot = New TreeNode(data)
>      Else
>         mRoot.Add(data)
>      End If
>   End Sub
>
>   Public Function Search(ByVal data As IComparable) As Object
>      Return Me.Search(data, Me.mRoot)
>   End Function
>
>   Private Function Search(ByVal data As IComparable, ByVal node As
> TreeNode) As Object
>
>      If node Is Nothing Then
>         Return Nothing
>      Else
>         Dim result As Integer = data.CompareTo(node.Data) '****** this is
> the error I get on this line :Object must be of type String.
>
>         If result = 0 Then
>            Return node.Data
>         ElseIf result < 0 Then
>            Return Me.Search(data, node.LeftNode)
>         Else
>            Return Me.Search(data, node.RightNode)
>         End If
>      End If
>
>   End Function
> End Class
> *****************************
> The class Person
> *****************************
> Public Class Persoon
>   Inherits BusinessObject
>   Implements IComparable
>
>   Private mVnaam As String
>   Private mAnaam As String
>
>   Public Sub New(ByVal Vnaam As String, ByVal Anaam As String)
>      Me.mVnaam = Vnaam
>      Me.mAnaam = Anaam
>   End Sub
>
>   Public Property Vnaam() As String
>      Get
>         Return Me.mVnaam
>      End Get
>      Set(ByVal value As String)
>         mVnaam = value
>      End Set
>   End Property
>
>   Public Property Anaam() As String
>      Get
>         Return Me.mAnaam
>      End Get
>      Set(ByVal value As String)
>         Me.mAnaam = value
>      End Set
>   End Property
>
>   Public Overrides Function IsValid() As Boolean
>      If Me.isValidVnaam() And Me.isValidAnaam() Then
>         Return True
>      Else
>         Return False
>      End If
>   End Function
>
>   Private Function isValidVnaam() As Boolean
>      If Me.Vnaam.Trim.Length > 0 Then
>         Return True
>      Else
>         Return False
>      End If
>   End Function
>
>   Private Function isValidAnaam() As Boolean
>      If Me.Anaam.Trim.Length > 0 Then
>         Return True
>      Else
>         Return False
>      End If
>   End Function
>
>   Public Overloads Function CompareTo(ByVal obj As Object) As Integer
> Implements System.IComparable.CompareTo
>      Return Me.mVnaam.CompareTo(CType(obj, Persoon).Vnaam)
>   End Function
> End Class
> **********************************
> The Form :
> **********************************
> Public Class frmBinarySearchTree
>
>   Private Sub btnExecute_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles btnExecute.Click
>      Dim bstLedenLijst As New BinarySearchTree
>      Dim bstLidnummer As New BinarySearchTree
>      Dim txtOutput As String = ""
>
>      bstLidnummer.Add("5")
>      bstLidnummer.Add("2")
>      bstLidnummer.Add("1")
>      bstLidnummer.Add("4")
>      bstLidnummer.Add("3")
>      txtOutput = bstLidnummer.Search("3") & vbCrLf
>
>      bstLedenLijst.Add(New Persoon("Nicole", "Kidman"))
>      bstLedenLijst.Add(New Persoon("Jamie-Lee", "Curtis"))
>      bstLedenLijst.Add(New Persoon("Demi", "Moore"))
>      bstLedenLijst.Add(New Persoon("Julia", "Roberts"))
>      bstLedenLijst.Add(New Persoon("Andie", "MacDowell"))
>
>      txtOutput &= bstLedenLijst.Search("Demi") ' & vbCrLf
>
>      Me.txtOutput.Text = txtOutput
>
>   End Sub
>
>   Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles btnExit.Click
>      Application.Exit()
>   End Sub
>
> End Class
>
>
>

28 Dec 2006 2:16 PM

Jay B. Harlow

Reviewing this, one more change:

    Public Function Search(ByVal data As T) As T
        Return Me.Search(data, Me.mRoot)
    End Function

    Private Function Search(ByVal data As T, ByVal node As TreeNode) As T

        If node Is Nothing Then
            Return Nothing
        Else
            Dim result As Integer = data.CompareTo(node.Data) '****** this
is the error I get on this line :Object must be of type String.

            If result = 0 Then
                Return node.Data
            ElseIf result < 0 Then
                Return Me.Search(data, node.LeftNode)
            Else
                Return Me.Search(data, node.RightNode)
            End If
        End If

Note that Search returns type T; this ensures that BinarySearchTree(Of T) is
type safe and performant. performant in that the data will not be boxed. (in
the case of BinarySearchTree(Of Integer))

Although I would recommend defining Search as:

    Public Function Search(ByVal match As Predicate(Of T)) As T

Or even:

    Public Delegate Function Predicate(Of T, V)(ByVal obj As T, ByVal value
As V) As Boolean

    Public Function Search(Of V)(ByVal value As V, ByVal match As
Predicate(Of T, V)) As T

Which I will leave as an exercise for you to complete...

--
Hope this helps
Jay B. Harlow
..NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net

Show quoteHide quote

"Jay B. Harlow" <Jay_Harlow_***@tsbradley.net> wrote in message
news:eIm21joKHHA.3268@TK2MSFTNGP04.phx.gbl...
> BenCoo,
> Interesting homework assignment; I miss those days...
>
> Anyway to answer your question:
>
>>      Dim bstLedenLijst As New BinarySearchTree
>>      Dim bstLidnummer As New BinarySearchTree
>>      Dim txtOutput As String = ""
>>
>>      bstLidnummer.Add("5")
>>      txtOutput = bstLidnummer.Search("3") & vbCrLf
>>
>>      bstLedenLijst.Add(New Persoon("Nicole", "Kidman"))
>>
>>      txtOutput &= bstLedenLijst.Search("Demi") ' & vbCrLf
>
> Ah! There's the Rub!
>
> bstLedenLijst contains a collection of Persoon objects, you are attempting
> to compare Persoon objects to a String object! You need to pass a Persoon
> object to bstLedenLijst.Search. I would recommend you change
> BinarySearchTree to a Generic class; changing this obscure runtime error
> into an obvious compile time error!
>
> Something like:
>
> Public Class BinarySearchTree(Of T As IComparable)
>
>    Private Class TreeNode
>        Private mData As T
>        Private mLeftNode As TreeNode
>        Private mRightNode As TreeNode
>
>        Public Sub New(ByVal data As T)
>            Me.mData = data
>        End Sub
>
>        Public ReadOnly Property Data() As T
>            Get
>                Return Me.mData
>            End Get
>        End Property
>
>        Public Property LeftNode() As TreeNode
>            Get
>                Return Me.mLeftNode
>            End Get
>            Set(ByVal value As TreeNode)
>                Me.mLeftNode = value
>            End Set
>        End Property
>
>        Public Property RightNode() As TreeNode
>            Get
>                Return Me.mRightNode
>            End Get
>            Set(ByVal value As TreeNode)
>                Me.mRightNode = value
>            End Set
>        End Property
>
>        Public Sub Add(ByVal data As T)
>            If data.CompareTo(Me.mData) <= 0 Then
>                If Me.mLeftNode Is Nothing Then
>                    Me.mLeftNode = New TreeNode(data)
>                Else
>                    Me.mLeftNode.Add(data)
>                End If
>            Else
>                If Me.mRightNode Is Nothing Then
>                    Me.mRightNode = New TreeNode(data)
>                Else
>                    Me.mRightNode.Add(data)
>                End If
>            End If
>        End Sub
>    End Class
>
>    Private mRoot As TreeNode
>
>    Public Sub Add(ByVal data As T)
>        If mRoot Is Nothing Then
>            mRoot = New TreeNode(data)
>        Else
>            mRoot.Add(data)
>        End If
>    End Sub
>
>    Public Function Search(ByVal data As T) As Object
>        Return Me.Search(data, Me.mRoot)
>    End Function
>
>    Private Function Search(ByVal data As T, ByVal node As TreeNode) As
> Object
>
>        If node Is Nothing Then
>            Return Nothing
>        Else
>            Dim result As Integer = data.CompareTo(node.Data) '****** this
> is the error I get on this line :Object must be of type String.
>
>            If result = 0 Then
>                Return node.Data
>            ElseIf result < 0 Then
>                Return Me.Search(data, node.LeftNode)
>            Else
>                Return Me.Search(data, node.RightNode)
>            End If
>        End If
>
>    End Function
> End Class
>
> Then when you define your trees, you give the type of tree they are!
>
>>      Dim bstLedenLijst As New BinarySearchTree(Of String)
>>      Dim bstLidnummer As New BinarySearchTree(Of Persoon)
>
> NOTE: You need VS 2005 for generics.
>
> --
> Hope this helps
> Jay B. Harlow
> .NET Application Architect, Enthusiast, & Evangelist
> T.S. Bradley - http://www.tsbradley.net
>
>
> "BenCoo" <teddy***@hotmail.com> wrote in message
> news:CNPkh.260824$tk1.5394486@phobos.telenet-ops.be...
>> Hello,
>>
>> In a Binary Search Tree I get the error : Object must be of type String
>>
>> if I run the form only with the   "Dim bstLidnummer As New
>> BinarySearchTree"
>> it works fine.
>>
>> Thanks for any help on this,
>>
>> Benny
>>
>> My BST-code lookes lokes this :
>> **************************************************
>> Class BST
>> **************************************************
>> Public Class BinarySearchTree
>>   Private Class TreeNode
>>      Private mData As IComparable
>>      Private mLeftNode As TreeNode
>>      Private mRightNode As TreeNode
>>
>>      Public Sub New(ByVal data As IComparable)
>>         Me.mData = data
>>      End Sub
>>
>>      Public ReadOnly Property Data() As IComparable
>>         Get
>>            Return Me.mData
>>         End Get
>>      End Property
>>
>>      Public Property LeftNode() As TreeNode
>>         Get
>>            Return Me.mLeftNode
>>         End Get
>>         Set(ByVal value As TreeNode)
>>            Me.mLeftNode = value
>>         End Set
>>      End Property
>>
>>      Public Property RightNode() As TreeNode
>>         Get
>>            Return Me.mRightNode
>>         End Get
>>         Set(ByVal value As TreeNode)
>>            Me.mRightNode = value
>>         End Set
>>      End Property
>>
>>      Public Sub Add(ByVal data As IComparable)
>>         If data.CompareTo(Me.mData) <= 0 Then
>>            If Me.mLeftNode Is Nothing Then
>>               Me.mLeftNode = New TreeNode(data)
>>            Else
>>               Me.mLeftNode.Add(data)
>>            End If
>>         Else
>>            If Me.mRightNode Is Nothing Then
>>               Me.mRightNode = New TreeNode(data)
>>            Else
>>               Me.mRightNode.Add(data)
>>            End If
>>         End If
>>      End Sub
>>   End Class
>>
>>   Private mRoot As TreeNode
>>
>>   Public Sub Add(ByVal data As IComparable)
>>      If mRoot Is Nothing Then
>>         mRoot = New TreeNode(data)
>>      Else
>>         mRoot.Add(data)
>>      End If
>>   End Sub
>>
>>   Public Function Search(ByVal data As IComparable) As Object
>>      Return Me.Search(data, Me.mRoot)
>>   End Function
>>
>>   Private Function Search(ByVal data As IComparable, ByVal node As
>> TreeNode) As Object
>>
>>      If node Is Nothing Then
>>         Return Nothing
>>      Else
>>         Dim result As Integer = data.CompareTo(node.Data) '****** this
>> is
>> the error I get on this line :Object must be of type String.
>>
>>         If result = 0 Then
>>            Return node.Data
>>         ElseIf result < 0 Then
>>            Return Me.Search(data, node.LeftNode)
>>         Else
>>            Return Me.Search(data, node.RightNode)
>>         End If
>>      End If
>>
>>   End Function
>> End Class
>> *****************************
>> The class Person
>> *****************************
>> Public Class Persoon
>>   Inherits BusinessObject
>>   Implements IComparable
>>
>>   Private mVnaam As String
>>   Private mAnaam As String
>>
>>   Public Sub New(ByVal Vnaam As String, ByVal Anaam As String)
>>      Me.mVnaam = Vnaam
>>      Me.mAnaam = Anaam
>>   End Sub
>>
>>   Public Property Vnaam() As String
>>      Get
>>         Return Me.mVnaam
>>      End Get
>>      Set(ByVal value As String)
>>         mVnaam = value
>>      End Set
>>   End Property
>>
>>   Public Property Anaam() As String
>>      Get
>>         Return Me.mAnaam
>>      End Get
>>      Set(ByVal value As String)
>>         Me.mAnaam = value
>>      End Set
>>   End Property
>>
>>   Public Overrides Function IsValid() As Boolean
>>      If Me.isValidVnaam() And Me.isValidAnaam() Then
>>         Return True
>>      Else
>>         Return False
>>      End If
>>   End Function
>>
>>   Private Function isValidVnaam() As Boolean
>>      If Me.Vnaam.Trim.Length > 0 Then
>>         Return True
>>      Else
>>         Return False
>>      End If
>>   End Function
>>
>>   Private Function isValidAnaam() As Boolean
>>      If Me.Anaam.Trim.Length > 0 Then
>>         Return True
>>      Else
>>         Return False
>>      End If
>>   End Function
>>
>>   Public Overloads Function CompareTo(ByVal obj As Object) As Integer
>> Implements System.IComparable.CompareTo
>>      Return Me.mVnaam.CompareTo(CType(obj, Persoon).Vnaam)
>>   End Function
>> End Class
>> **********************************
>> The Form :
>> **********************************
>> Public Class frmBinarySearchTree
>>
>>   Private Sub btnExecute_Click(ByVal sender As System.Object, ByVal e As
>> System.EventArgs) Handles btnExecute.Click
>>      Dim bstLedenLijst As New BinarySearchTree
>>      Dim bstLidnummer As New BinarySearchTree
>>      Dim txtOutput As String = ""
>>
>>      bstLidnummer.Add("5")
>>      bstLidnummer.Add("2")
>>      bstLidnummer.Add("1")
>>      bstLidnummer.Add("4")
>>      bstLidnummer.Add("3")
>>      txtOutput = bstLidnummer.Search("3") & vbCrLf
>>
>>      bstLedenLijst.Add(New Persoon("Nicole", "Kidman"))
>>      bstLedenLijst.Add(New Persoon("Jamie-Lee", "Curtis"))
>>      bstLedenLijst.Add(New Persoon("Demi", "Moore"))
>>      bstLedenLijst.Add(New Persoon("Julia", "Roberts"))
>>      bstLedenLijst.Add(New Persoon("Andie", "MacDowell"))
>>
>>      txtOutput &= bstLedenLijst.Search("Demi") ' & vbCrLf
>>
>>      Me.txtOutput.Text = txtOutput
>>
>>   End Sub
>>
>>   Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As
>> System.EventArgs) Handles btnExit.Click
>>      Application.Exit()
>>   End Sub
>>
>> End Class
>>
>>
>>
>

29 Dec 2006 2:14 AM

BenCoo

Thank you for your quick response; I solved afther the poste was made the
promlem this way ..

Dim zoekPersoon As New Persoon(Me.txtZoek.Text, "")

Console.WriteLine(bstLedenLijst.Search(zoekPersoon))

Show quoteHide quote

"Jay B. Harlow" <Jay_Harlow_***@tsbradley.net> schreef in bericht
news:eIm21joKHHA.3268@TK2MSFTNGP04.phx.gbl...
> BenCoo,
> Interesting homework assignment; I miss those days...
>
> Anyway to answer your question:
>
>>      Dim bstLedenLijst As New BinarySearchTree
>>      Dim bstLidnummer As New BinarySearchTree
>>      Dim txtOutput As String = ""
>>
>>      bstLidnummer.Add("5")
>>      txtOutput = bstLidnummer.Search("3") & vbCrLf
>>
>>      bstLedenLijst.Add(New Persoon("Nicole", "Kidman"))
>>
>>      txtOutput &= bstLedenLijst.Search("Demi") ' & vbCrLf
>
> Ah! There's the Rub!
>
> bstLedenLijst contains a collection of Persoon objects, you are attempting
> to compare Persoon objects to a String object! You need to pass a Persoon
> object to bstLedenLijst.Search. I would recommend you change
> BinarySearchTree to a Generic class; changing this obscure runtime error
> into an obvious compile time error!
>
> Something like:
>
> Public Class BinarySearchTree(Of T As IComparable)
>
>    Private Class TreeNode
>        Private mData As T
>        Private mLeftNode As TreeNode
>        Private mRightNode As TreeNode
>
>        Public Sub New(ByVal data As T)
>            Me.mData = data
>        End Sub
>
>        Public ReadOnly Property Data() As T
>            Get
>                Return Me.mData
>            End Get
>        End Property
>
>        Public Property LeftNode() As TreeNode
>            Get
>                Return Me.mLeftNode
>            End Get
>            Set(ByVal value As TreeNode)
>                Me.mLeftNode = value
>            End Set
>        End Property
>
>        Public Property RightNode() As TreeNode
>            Get
>                Return Me.mRightNode
>            End Get
>            Set(ByVal value As TreeNode)
>                Me.mRightNode = value
>            End Set
>        End Property
>
>        Public Sub Add(ByVal data As T)
>            If data.CompareTo(Me.mData) <= 0 Then
>                If Me.mLeftNode Is Nothing Then
>                    Me.mLeftNode = New TreeNode(data)
>                Else
>                    Me.mLeftNode.Add(data)
>                End If
>            Else
>                If Me.mRightNode Is Nothing Then
>                    Me.mRightNode = New TreeNode(data)
>                Else
>                    Me.mRightNode.Add(data)
>                End If
>            End If
>        End Sub
>    End Class
>
>    Private mRoot As TreeNode
>
>    Public Sub Add(ByVal data As T)
>        If mRoot Is Nothing Then
>            mRoot = New TreeNode(data)
>        Else
>            mRoot.Add(data)
>        End If
>    End Sub
>
>    Public Function Search(ByVal data As T) As Object
>        Return Me.Search(data, Me.mRoot)
>    End Function
>
>    Private Function Search(ByVal data As T, ByVal node As TreeNode) As
> Object
>
>        If node Is Nothing Then
>            Return Nothing
>        Else
>            Dim result As Integer = data.CompareTo(node.Data) '****** this
> is the error I get on this line :Object must be of type String.
>
>            If result = 0 Then
>                Return node.Data
>            ElseIf result < 0 Then
>                Return Me.Search(data, node.LeftNode)
>            Else
>                Return Me.Search(data, node.RightNode)
>            End If
>        End If
>
>    End Function
> End Class
>
> Then when you define your trees, you give the type of tree they are!
>
>>      Dim bstLedenLijst As New BinarySearchTree(Of String)
>>      Dim bstLidnummer As New BinarySearchTree(Of Persoon)
>
> NOTE: You need VS 2005 for generics.
>
> --
> Hope this helps
> Jay B. Harlow
> .NET Application Architect, Enthusiast, & Evangelist
> T.S. Bradley - http://www.tsbradley.net
>
>
> "BenCoo" <teddy***@hotmail.com> wrote in message
> news:CNPkh.260824$tk1.5394486@phobos.telenet-ops.be...
>> Hello,
>>
>> In a Binary Search Tree I get the error : Object must be of type String
>>
>> if I run the form only with the   "Dim bstLidnummer As New
>> BinarySearchTree"
>> it works fine.
>>
>> Thanks for any help on this,
>>
>> Benny
>>
>> My BST-code lookes lokes this :
>> **************************************************
>> Class BST
>> **************************************************
>> Public Class BinarySearchTree
>>   Private Class TreeNode
>>      Private mData As IComparable
>>      Private mLeftNode As TreeNode
>>      Private mRightNode As TreeNode
>>
>>      Public Sub New(ByVal data As IComparable)
>>         Me.mData = data
>>      End Sub
>>
>>      Public ReadOnly Property Data() As IComparable
>>         Get
>>            Return Me.mData
>>         End Get
>>      End Property
>>
>>      Public Property LeftNode() As TreeNode
>>         Get
>>            Return Me.mLeftNode
>>         End Get
>>         Set(ByVal value As TreeNode)
>>            Me.mLeftNode = value
>>         End Set
>>      End Property
>>
>>      Public Property RightNode() As TreeNode
>>         Get
>>            Return Me.mRightNode
>>         End Get
>>         Set(ByVal value As TreeNode)
>>            Me.mRightNode = value
>>         End Set
>>      End Property
>>
>>      Public Sub Add(ByVal data As IComparable)
>>         If data.CompareTo(Me.mData) <= 0 Then
>>            If Me.mLeftNode Is Nothing Then
>>               Me.mLeftNode = New TreeNode(data)
>>            Else
>>               Me.mLeftNode.Add(data)
>>            End If
>>         Else
>>            If Me.mRightNode Is Nothing Then
>>               Me.mRightNode = New TreeNode(data)
>>            Else
>>               Me.mRightNode.Add(data)
>>            End If
>>         End If
>>      End Sub
>>   End Class
>>
>>   Private mRoot As TreeNode
>>
>>   Public Sub Add(ByVal data As IComparable)
>>      If mRoot Is Nothing Then
>>         mRoot = New TreeNode(data)
>>      Else
>>         mRoot.Add(data)
>>      End If
>>   End Sub
>>
>>   Public Function Search(ByVal data As IComparable) As Object
>>      Return Me.Search(data, Me.mRoot)
>>   End Function
>>
>>   Private Function Search(ByVal data As IComparable, ByVal node As
>> TreeNode) As Object
>>
>>      If node Is Nothing Then
>>         Return Nothing
>>      Else
>>         Dim result As Integer = data.CompareTo(node.Data) '****** this
>> is
>> the error I get on this line :Object must be of type String.
>>
>>         If result = 0 Then
>>            Return node.Data
>>         ElseIf result < 0 Then
>>            Return Me.Search(data, node.LeftNode)
>>         Else
>>            Return Me.Search(data, node.RightNode)
>>         End If
>>      End If
>>
>>   End Function
>> End Class
>> *****************************
>> The class Person
>> *****************************
>> Public Class Persoon
>>   Inherits BusinessObject
>>   Implements IComparable
>>
>>   Private mVnaam As String
>>   Private mAnaam As String
>>
>>   Public Sub New(ByVal Vnaam As String, ByVal Anaam As String)
>>      Me.mVnaam = Vnaam
>>      Me.mAnaam = Anaam
>>   End Sub
>>
>>   Public Property Vnaam() As String
>>      Get
>>         Return Me.mVnaam
>>      End Get
>>      Set(ByVal value As String)
>>         mVnaam = value
>>      End Set
>>   End Property
>>
>>   Public Property Anaam() As String
>>      Get
>>         Return Me.mAnaam
>>      End Get
>>      Set(ByVal value As String)
>>         Me.mAnaam = value
>>      End Set
>>   End Property
>>
>>   Public Overrides Function IsValid() As Boolean
>>      If Me.isValidVnaam() And Me.isValidAnaam() Then
>>         Return True
>>      Else
>>         Return False
>>      End If
>>   End Function
>>
>>   Private Function isValidVnaam() As Boolean
>>      If Me.Vnaam.Trim.Length > 0 Then
>>         Return True
>>      Else
>>         Return False
>>      End If
>>   End Function
>>
>>   Private Function isValidAnaam() As Boolean
>>      If Me.Anaam.Trim.Length > 0 Then
>>         Return True
>>      Else
>>         Return False
>>      End If
>>   End Function
>>
>>   Public Overloads Function CompareTo(ByVal obj As Object) As Integer
>> Implements System.IComparable.CompareTo
>>      Return Me.mVnaam.CompareTo(CType(obj, Persoon).Vnaam)
>>   End Function
>> End Class
>> **********************************
>> The Form :
>> **********************************
>> Public Class frmBinarySearchTree
>>
>>   Private Sub btnExecute_Click(ByVal sender As System.Object, ByVal e As
>> System.EventArgs) Handles btnExecute.Click
>>      Dim bstLedenLijst As New BinarySearchTree
>>      Dim bstLidnummer As New BinarySearchTree
>>      Dim txtOutput As String = ""
>>
>>      bstLidnummer.Add("5")
>>      bstLidnummer.Add("2")
>>      bstLidnummer.Add("1")
>>      bstLidnummer.Add("4")
>>      bstLidnummer.Add("3")
>>      txtOutput = bstLidnummer.Search("3") & vbCrLf
>>
>>      bstLedenLijst.Add(New Persoon("Nicole", "Kidman"))
>>      bstLedenLijst.Add(New Persoon("Jamie-Lee", "Curtis"))
>>      bstLedenLijst.Add(New Persoon("Demi", "Moore"))
>>      bstLedenLijst.Add(New Persoon("Julia", "Roberts"))
>>      bstLedenLijst.Add(New Persoon("Andie", "MacDowell"))
>>
>>      txtOutput &= bstLedenLijst.Search("Demi") ' & vbCrLf
>>
>>      Me.txtOutput.Text = txtOutput
>>
>>   End Sub
>>
>>   Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As
>> System.EventArgs) Handles btnExit.Click
>>      Application.Exit()
>>   End Sub
>>
>> End Class
>>
>>
>>
>

28 Dec 2006 2:05 PM

Jay B. Harlow

Doh!

Clicked send too soon. I had the trees backwards:

Dim bstLedenLijst As New BinarySearchTree(Of Persoon)
Dim bstLidnummer As New BinarySearchTree(Of String)

Of course this demonstrated the immediate & obvious compile time error I
suggested ;-)

--
Hope this helps
Jay B. Harlow
..NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net

Show quoteHide quote

"BenCoo" <teddy***@hotmail.com> wrote in message
news:CNPkh.260824$tk1.5394486@phobos.telenet-ops.be...
> Hello,
>
> In a Binary Search Tree I get the error : Object must be of type String
>
> if I run the form only with the   "Dim bstLidnummer As New
> BinarySearchTree"
> it works fine.
>
> Thanks for any help on this,
>
> Benny
>
> My BST-code lookes lokes this :
> **************************************************
> Class BST
> **************************************************
> Public Class BinarySearchTree
>   Private Class TreeNode
>      Private mData As IComparable
>      Private mLeftNode As TreeNode
>      Private mRightNode As TreeNode
>
>      Public Sub New(ByVal data As IComparable)
>         Me.mData = data
>      End Sub
>
>      Public ReadOnly Property Data() As IComparable
>         Get
>            Return Me.mData
>         End Get
>      End Property
>
>      Public Property LeftNode() As TreeNode
>         Get
>            Return Me.mLeftNode
>         End Get
>         Set(ByVal value As TreeNode)
>            Me.mLeftNode = value
>         End Set
>      End Property
>
>      Public Property RightNode() As TreeNode
>         Get
>            Return Me.mRightNode
>         End Get
>         Set(ByVal value As TreeNode)
>            Me.mRightNode = value
>         End Set
>      End Property
>
>      Public Sub Add(ByVal data As IComparable)
>         If data.CompareTo(Me.mData) <= 0 Then
>            If Me.mLeftNode Is Nothing Then
>               Me.mLeftNode = New TreeNode(data)
>            Else
>               Me.mLeftNode.Add(data)
>            End If
>         Else
>            If Me.mRightNode Is Nothing Then
>               Me.mRightNode = New TreeNode(data)
>            Else
>               Me.mRightNode.Add(data)
>            End If
>         End If
>      End Sub
>   End Class
>
>   Private mRoot As TreeNode
>
>   Public Sub Add(ByVal data As IComparable)
>      If mRoot Is Nothing Then
>         mRoot = New TreeNode(data)
>      Else
>         mRoot.Add(data)
>      End If
>   End Sub
>
>   Public Function Search(ByVal data As IComparable) As Object
>      Return Me.Search(data, Me.mRoot)
>   End Function
>
>   Private Function Search(ByVal data As IComparable, ByVal node As
> TreeNode) As Object
>
>      If node Is Nothing Then
>         Return Nothing
>      Else
>         Dim result As Integer = data.CompareTo(node.Data) '****** this is
> the error I get on this line :Object must be of type String.
>
>         If result = 0 Then
>            Return node.Data
>         ElseIf result < 0 Then
>            Return Me.Search(data, node.LeftNode)
>         Else
>            Return Me.Search(data, node.RightNode)
>         End If
>      End If
>
>   End Function
> End Class
> *****************************
> The class Person
> *****************************
> Public Class Persoon
>   Inherits BusinessObject
>   Implements IComparable
>
>   Private mVnaam As String
>   Private mAnaam As String
>
>   Public Sub New(ByVal Vnaam As String, ByVal Anaam As String)
>      Me.mVnaam = Vnaam
>      Me.mAnaam = Anaam
>   End Sub
>
>   Public Property Vnaam() As String
>      Get
>         Return Me.mVnaam
>      End Get
>      Set(ByVal value As String)
>         mVnaam = value
>      End Set
>   End Property
>
>   Public Property Anaam() As String
>      Get
>         Return Me.mAnaam
>      End Get
>      Set(ByVal value As String)
>         Me.mAnaam = value
>      End Set
>   End Property
>
>   Public Overrides Function IsValid() As Boolean
>      If Me.isValidVnaam() And Me.isValidAnaam() Then
>         Return True
>      Else
>         Return False
>      End If
>   End Function
>
>   Private Function isValidVnaam() As Boolean
>      If Me.Vnaam.Trim.Length > 0 Then
>         Return True
>      Else
>         Return False
>      End If
>   End Function
>
>   Private Function isValidAnaam() As Boolean
>      If Me.Anaam.Trim.Length > 0 Then
>         Return True
>      Else
>         Return False
>      End If
>   End Function
>
>   Public Overloads Function CompareTo(ByVal obj As Object) As Integer
> Implements System.IComparable.CompareTo
>      Return Me.mVnaam.CompareTo(CType(obj, Persoon).Vnaam)
>   End Function
> End Class
> **********************************
> The Form :
> **********************************
> Public Class frmBinarySearchTree
>
>   Private Sub btnExecute_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles btnExecute.Click
>      Dim bstLedenLijst As New BinarySearchTree
>      Dim bstLidnummer As New BinarySearchTree
>      Dim txtOutput As String = ""
>
>      bstLidnummer.Add("5")
>      bstLidnummer.Add("2")
>      bstLidnummer.Add("1")
>      bstLidnummer.Add("4")
>      bstLidnummer.Add("3")
>      txtOutput = bstLidnummer.Search("3") & vbCrLf
>
>      bstLedenLijst.Add(New Persoon("Nicole", "Kidman"))
>      bstLedenLijst.Add(New Persoon("Jamie-Lee", "Curtis"))
>      bstLedenLijst.Add(New Persoon("Demi", "Moore"))
>      bstLedenLijst.Add(New Persoon("Julia", "Roberts"))
>      bstLedenLijst.Add(New Persoon("Andie", "MacDowell"))
>
>      txtOutput &= bstLedenLijst.Search("Demi") ' & vbCrLf
>
>      Me.txtOutput.Text = txtOutput
>
>   End Sub
>
>   Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles btnExit.Click
>      Application.Exit()
>   End Sub
>
> End Class
>
>
>

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