form1.vb

来自「Visual Basic .NET程序设计教程源代码」· VB 代码 · 共 85 行

Imports System.Math
Public Class Form1
    Inherits System.Windows.Forms.Form
    Public Sub Newton(ByVal x0 As Double, ByVal x As Double, ByVal eps As Double)
        '迭代初值x0，求得的根x，精度eps
        Dim fx, f1x As Double
        Do
            fx = 3 * x0 * x0 * x0 - 4 * x0 * x0 - 5 * x0 + 13
            f1x = 9 * x0 * x0 - 8 * x0 - 5
            x = x0 - fx / f1x
            If Abs(x - x0) < eps Then Exit Do
            x0 = x
        Loop
        TextBox1.Text = x
    End Sub
#Region " Windows 窗体设计器生成的代码 "

    Public Sub New()
        MyBase.New()

        '该调用是 Windows 窗体设计器所必需的。
        InitializeComponent()

        '在 InitializeComponent() 调用之后添加任何初始化

    End Sub

    '窗体重写处置以清理组件列表。
    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

    'Windows 窗体设计器所必需的
    Private components As System.ComponentModel.IContainer

    '注意：以下过程是 Windows 窗体设计器所必需的
    '可以使用 Windows 窗体设计器修改此过程。
    '不要使用代码编辑器修改它。
    Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
    Friend WithEvents Label1 As System.Windows.Forms.Label
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.TextBox1 = New System.Windows.Forms.TextBox
        Me.Label1 = New System.Windows.Forms.Label
        Me.SuspendLayout()
        '
        'TextBox1
        '
        Me.TextBox1.Location = New System.Drawing.Point(48, 40)
        Me.TextBox1.Name = "TextBox1"
        Me.TextBox1.Size = New System.Drawing.Size(184, 21)
        Me.TextBox1.TabIndex = 0
        Me.TextBox1.Text = ""
        '
        'Label1
        '
        Me.Label1.Location = New System.Drawing.Point(8, 8)
        Me.Label1.Name = "Label1"
        Me.Label1.Size = New System.Drawing.Size(152, 23)
        Me.Label1.TabIndex = 1
        Me.Label1.Text = "牛顿切线法所求得的根为 "
        '
        'Form1
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(6, 14)
        Me.ClientSize = New System.Drawing.Size(292, 273)
        Me.Controls.Add(Me.Label1)
        Me.Controls.Add(Me.TextBox1)
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)

    End Sub

#End Region
    Private Sub Form1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Click
        Dim root As Double
        Call Newton(3.0#, root, 0.00001)
    End Sub
End Class