d4r4.frm

来自「常用数值算法集哈」· FRM 代码 · 共 87 行

VERSION 5.00
Begin VB.Form Form1 
   Caption         =   "Form1"
   ClientHeight    =   2895
   ClientLeft      =   60
   ClientTop       =   345
   ClientWidth     =   4110
   LinkTopic       =   "Form1"
   ScaleHeight     =   2895
   ScaleWidth      =   4110
   StartUpPosition =   3  'Windows Default
   Begin VB.CommandButton Command1 
      Caption         =   "Command1"
      Height          =   375
      Left            =   2280
      TabIndex        =   0
      Top             =   2160
      Width           =   1455
   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 D4R4
    'Driver for routine FACTLN
    Dim ACTUAL(5), X(5)
    ACTUAL(1) = 0.693147
    ACTUAL(2) = 4.787492
    ACTUAL(3) = 15.10441
    ACTUAL(4) = 27.89927
    ACTUAL(5) = 42.33562
    X(1) = 2
    X(2) = 5
    X(3) = 10
    X(4) = 15
    X(5) = 20
    Print
    Print "   X        Actual      FACTLN(X)"
    For I = 1 To 5
        Print Tab(4); Format$(X(I), "#0");
        Print Tab(12); Format$(ACTUAL(I), "###.000000");
        Print Tab(25); Format$(FACTLN(X(I)), "###.000000")
    Next I
End Sub
Function FACTLN(N)
    Dim A(100)
    For I = 1 To 100
        A(I) = -1#
    Next I
    If N < 0 Then
    Print "negative factorial"
    Exit Function
    End If
    If N <= 99 Then
        If A(N + 1) < 0# Then A(N + 1) = GAMMLN(N + 1#)
        FACTLN = A(N + 1)
    Else
        FACTLN = GAMMLN(N + 1#)
    End If
End Function
  Function GAMMLN(XX)
      Dim COF(6)
      COF(1) = 76.18009173
      COF(2) = -86.50532033
      COF(3) = 24.01409822
      COF(4) = -1.231739516
      COF(5) = 0.00120858003
      COF(6) = -0.00000536382
      STP = 2.50662827465
      HALF = 0.5
      ONE = 1#
      FPF = 5.5
      X = XX - ONE
      TMP = X + FPF
      TMP = (X + HALF) * Log(TMP) - TMP
      SER = ONE
      For J = 1 To 6
          X = X + ONE
          SER = SER + COF(J) / X
    Next J
      GAMMLN = TMP + Log(STP * SER)
   End Function