bs.txt

常用的数值算法的VB程序

Function BS(N, A)
    Dim B(20)
    If A = 0# Then
       If N / 2 = N / 2# Then
         B(N) = 0#
         GoTo 15
       End If
       B(N) = 2# / N
       GoTo 15
    End If
    If Abs(A) < 8# Then
       DEL = 0.00000001
       If N / 2 <> N / 2# Then
         R = 2# / N
         EPS = R * DEL
         S = R
         AK = 0#
         A2 = A * A
5        AK = AK + 2#
         R = R * A2 * (N + AK - 2#) / (AK * (AK - 1#) * (N + AK))
         S = S + R
         If R > EPS Then GoTo 5
         B(N) = S + R
         GoTo 15
       End If
       R = 2# * A / (N + 1#)
       OMEG = Abs(R * DEL)
       S = R
       AK = 1#
       A2 = A * A
6      AK = AK + 2#
       R = R * A2 * (N + AK - 2#) / (AK * (AK - 1#) * (N + AK))
       S = S + R
       If Abs(R) > OMEG Then GoTo 6
       B(N) = -(S + R)
       GoTo 15
    End If
    DA = 1# / A
    AJP = DA * Exp(A)
    AJM = (DA * DA) / AJP
    B(1) = AJP - AJM
    If N = 1 Then GoTo 15
    Q1 = -1#
    Q2 = 1#
    For M = 2 To N
        B(M) = Q1 * AJP - AJM + Q2 * DA * B(M - 1)
        Q1 = -Q1
        Q2 = Q2 + 1#
    Next M
15  BS = B(N)
End Function