逐次代入法

时间：2011-02-16 来源：xp44m

代码 Public Class Successive
    Dim eps As Double = 0.001
    Dim Iteration As Integer = 1000

    Public Sub New()
    End Sub

    Public Sub New(ByVal eps As Double, ByVal iteration As Integer)
        Me.eps = eps
        Me.Iteration = iteration
    End Sub

    Public Function Solution(ByVal G As Func(Of Double, Double), ByVal x As Double) As Double
        Dim i As Integer = 0

        Dim x_new, x_old As Double
        x_old = x
        Do
            i += 1
            x_new = G(x_old)
            If Math.Abs(x_old - x_new) < eps Then Return x_new
            x_old = x_new
        Loop While i < Iteration
        Throw New Exception()
    End Function
End Class

测试代码，或者说客户代码：

方程x=0.3*exp(x)在x=0.5附近有一个根。用逐次代入法求这个根的真值。eps=1e-8

代码 Imports System.Math
Module Module1

    Sub Main()
        Dim substitution As New Successive
        Dim sol = substitution.Solution(Function(x) 0.3 * Exp(x), 0.5)
        Console.WriteLine(sol)
        Console.ReadLine()
    End Sub

End Module

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