d4r23.frm

来自「常用数值算法集哈」· FRM 代码 · 共 78 行

VERSION 5.00
Begin VB.Form Form1 
   Caption         =   "Form1"
   ClientHeight    =   2700
   ClientLeft      =   60
   ClientTop       =   345
   ClientWidth     =   3765
   LinkTopic       =   "Form1"
   ScaleHeight     =   2700
   ScaleWidth      =   3765
   StartUpPosition =   3  'Windows Default
   Begin VB.CommandButton Command1 
      Caption         =   "Command1"
      Height          =   375
      Left            =   2040
      TabIndex        =   0
      Top             =   2040
      Width           =   1335
   End
End
Attribute VB_Name = "Form1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Private Sub Command1_Click()
    'PROGRAM D4R23
    'Driver for routine BESSI1
    Dim ACTUAL(5), X(5)
    ACTUAL(1) = 0.1005008
    ACTUAL(2) = 0.5651592
    ACTUAL(3) = 0.7146779
    ACTUAL(4) = 1.590637
    ACTUAL(5) = 24.33564
    X(1) = 0.2
    X(2) = 1#
    X(3) = 1.2
    X(4) = 2#
    X(5) = 5#
    Print
    Print "    X       Actual         BESSI1(X)"
    For I = 1 To 5
        Print Tab(4); Format$(X(I), "#0.##");
        Print Tab(10); Format$(ACTUAL(I), ".0000000E+00");
        Print Tab(26); Format$(BESSI1(X(I)), ".0000000E+00")
    Next I
End Sub
Function BESSI1(X)
    P1 = 0.5
    P2 = 0.87890594
    P3 = 0.51498869
    P4 = 0.15084934
    P5 = 0.02658733
    P6 = 0.00301532
    P7 = 0.00032411
    Q1 = 0.39894228
    Q2 = -0.03988024
    Q3 = -0.00362018
    Q4 = 0.00163801
    Q5 = -0.01031555
    Q6 = 0.02282967
    Q7 = -0.02895312
    Q8 = 0.01787654
    Q9 = -0.00420059
    If Abs(X) < 3.75 Then
        Y = (X / 3.75) ^ 2
        AAA = Y * (P4 + Y * (P5 + Y * (P6 + Y * P7)))
        BESSI1 = X * (P1 + Y * (P2 + Y * (P3 + AAA)))
    Else
        AX = Abs(X)
        Y = 3.75 / AX
        AAA = Exp(AX) / Sqr(AX)
        BBB = Y * (Q5 + Y * (Q6 + Y * (Q7 + Y * (Q8 + Y * Q9))))
        BESSI1 = AAA * (Q1 + Y * (Q2 + Y * (Q3 + Y * (Q4 + BBB))))
    End If
End Function