d4r2.frm

来自「常用数值算法集哈」· FRM 代码 · 共 90 行

VERSION 5.00
Begin VB.Form Form1 
   Caption         =   "Form1"
   ClientHeight    =   3195
   ClientLeft      =   60
   ClientTop       =   345
   ClientWidth     =   4680
   LinkTopic       =   "Form1"
   ScaleHeight     =   3195
   ScaleWidth      =   4680
   StartUpPosition =   3  'Windows Default
   Begin VB.CommandButton Command1 
      Caption         =   "Command1"
      Height          =   375
      Left            =   2880
      TabIndex        =   0
      Top             =   2640
      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 D4R2
    'Driver for routine FACTRL
    Dim ACTUAL(5), X(5)
    ACTUAL(1) = 6
    ACTUAL(2) = 24#
    ACTUAL(3) = 120#
    ACTUAL(4) = 720#
    ACTUAL(5) = 5040#
    X(1) = 3
    X(2) = 4
    X(3) = 5
    X(4) = 6
    X(5) = 7
    Print
    Print "    N     Actual      FACVAL(X)"
    For I = 1 To 5
        Print Tab(4); Format$(X(I), "#0.0#");
        Print Tab(12); Format$(ACTUAL(I), "####.0");
        Print Tab(25); Format$(FACTRL(X(I)), "####.0")
    Next I
End Sub
Function FACTRL(N)
    Dim A(33)
    NTOP = 0
    A(1) = 1#
    If N < 0 Then
        Print "negative factorial"
        Exit Function
    ElseIf N <= NTOP Then
        FACTRL = A(N + 1)
    ElseIf N <= 32 Then
        For J = NTOP + 1 To N
            A(J + 1) = J * A(J)
        Next J
        NTOP = N
        FACTRL = A(N + 1)
    Else
        FACTRL = Exp(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