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標題: [分享] 運算子的重載 [打印本頁]
作者: 呆呆    時間: 2010-12-4 12:23     標題: 運算子的重載

VB.2005 以上有一項不錯用的功能,叫運算子的重載
什麼是運算子的重載
其實就是運算符號的重新定義
這在數學上很常見
一般我們在數學上 + - * / 這些東西是指數字的 加減乘除
但如果到了向量,或矩陣,或是虛數,這些符號就重新定義了
因為向量的加減乘除法和純量顯然有很大的不同,所以
A向量+B向量的程式碼不會寫成 C = A+B
但我們為了要使程式碼簡單易明白,所以我們也很想要這樣寫,那就必需重新定義運算子

[ <attributes> ] Public [ Overloads ] Shared [ Shadows ] _
[ Widening | Narrowing ] Operator symbol ( operands ) As type
...
End Operator
那這個要怎麼用,我們可以新增一個WindowsForm 專案
然後在該專案中再新增一個 Vector3D 類別如下
  1. Public Class Vector3D

  3.     Private mXValue As Double
  4.     Public Property XValue() As Double
  5.         Get
  6.             Return mXValue
  7.         End Get
  8.         Set(ByVal value As Double)
  9.             mXValue = value
  10.         End Set
  11.     End Property

  13.     Private mYvalue As Double
  14.     Public Property YValue() As Double
  15.         Get
  16.             Return mYvalue
  17.         End Get
  18.         Set(ByVal value As Double)
  19.             mYvalue = value
  20.         End Set
  21.     End Property

  23.     Private mZvalue As Double
  24.     Public Property ZValue() As Double
  25.         Get
  26.             Return mZvalue
  27.         End Get
  28.         Set(ByVal value As Double)
  29.             mZvalue = value
  30.         End Set
  31.     End Property

  33.     Public ReadOnly Property NormOfVector() As Double
  34.         Get
  35.             Return Math.Sqrt(XValue * XValue + YValue * YValue + ZValue * ZValue)
  36.         End Get
  37.     End Property

  39.     Public Sub New(ByVal x As Double, ByVal y As Double, ByVal z As Double)

  41.         mXValue = x
  42.         mYvalue = y
  43.         mZvalue = z

  45.     End Sub

  47.     Public Sub New()
  48.         XValue = 0
  49.         YValue = 0
  50.         ZValue = 0
  51.     End Sub

  53.     Public Shared Operator +(ByVal A As Vector3D, ByVal B As Vector3D) As Vector3D

  55.         Return New Vector3D(A.XValue + B.XValue, A.YValue + B.YValue, A.ZValue + B.ZValue)

  57.     End Operator


  60.     Public Shared Operator -(ByVal A As Vector3D, ByVal B As Vector3D) As Vector3D

  62.         Return New Vector3D(A.XValue - B.XValue, A.YValue - B.YValue, A.ZValue - B.ZValue)

  64.     End Operator

  66.     '外積
  67.     Public Shared Operator *(ByVal A As Vector3D, ByVal B As Vector3D) As Vector3D
  68.         Dim tmpVector As New Vector3D

  70.         With tmpVector
  71.             .XValue = A.YValue * B.ZValue - A.ZValue * B.YValue
  72.             .YValue = -(A.XValue * B.ZValue - A.ZValue * B.XValue)
  73.             .ZValue = A.XValue * B.YValue - A.YValue * B.XValue
  74.         End With
  75.         Return tmpVector
  76.     End Operator


  79.     '內積
  80.     Public Shared Operator ^(ByVal A As Vector3D, ByVal B As Vector3D) As Double
  81.         Return A.XValue * B.XValue + A.YValue * +B.YValue + A.ZValue * B.ZValue
  82.     End Operator


  85.     Public Shared Function AngleBetweenTwoVector(ByVal A As Vector3D, ByVal B As Vector3D) As Double

  87.         Return Math.Acos((A ^ B) / (A.NormOfVector * B.NormOfVector)) * 180 / Math.PI

  89.     End Function


  92.     Public Overrides Function ToString() As String

  94.         If Me.YValue < 0 And Me.ZValue < 0 Then
  95.             Return Me.XValue & "i - " & -Me.YValue & "j - " & -Me.ZValue & "k"
  96.         End If

  98.         If Me.YValue < 0 And Me.ZValue >= 0 Then
  99.             Return Me.XValue & "i - " & -Me.YValue & "j + " & Me.ZValue & "k"
  100.         End If

  102.         If Me.YValue >= 0 And Me.ZValue < 0 Then
  103.             Return Me.XValue & "i + " & Me.YValue & "j - " & -Me.ZValue & "k"
  104.         End If

  106.         Return Me.XValue & "i + " & Me.YValue & "j + " & Me.ZValue & "k"

  108.     End Function


  111. End Class
複製代碼
作者: 呆呆    時間: 2010-12-4 12:30

上面的程式碼我們重定義了乘法的內外積和加減法
還有一個二向量的夾角分享方法
因為向量沒有除法所以不用定義,而乘法分為內外積二種
所以我們可以在 WindowsForm 上寫下以下程式碼
  1. Public Class Form1

  3.     Private A As New Vector3D(2, 3, 2)
  4.     Private B As New Vector3D(1, 2, -1)
  5.     Private C As New Vector3D
  6.     Private D As Double
  7.     Private H As Double

  9.     Private fnt As Font

  11.     Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

  13.         fnt = New Font("新細明體", 30)

  15.         C = A * B '外積
  16.         D = A ^ B '內樍
  17.         H = Vector3D.AngleBetweenTwoVector(A, B) '夾角

  19.     End Sub


  22.     Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint

  24.         Dim g As Graphics = e.Graphics

  26.         g.DrawString("二向量外積為   " & C.ToString, fnt, New SolidBrush(Color.Black), 10, 100)
  27.         g.DrawString("二向量內積為   " & D.ToString, fnt, New SolidBrush(Color.Black), 10, 200)
  28.         g.DrawString("二向量夾角為   " & H.ToString & " 度", fnt, New SolidBrush(Color.Black), 10, 300)

  30.     End Sub

  32. End Class
複製代碼
執行結果如下
作者: 呆呆    時間: 2010-12-4 12:34

看起來是不是比較符合我們一般算數學的符號



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