bessy0.txt

常用的数值算法的VB程序

Function BESSY0(X)
    P1 = 1#:                    P2 = -0.001098628627
    P3 = 0.00002734510407:      P4 = -0.000002073370639
    P5 = 2.093887211E-07
    Q1 = -0.01562499995:        Q2 = 0.0001430488765
    Q3 = -0.000006911147651:    Q4 = 7.621095161E-07
    Q5 = -9.34945152E-08
    R1 = -2957821389#:          R2 = 7062834065#
    R3 = -512359803.6:          R4 = 10879881.29
    R5 = -86327.92757:          R6 = 228.4622733
    S1 = 40076544269#:          S2 = 745249964.8
    S3 = 7189466.438:           S4 = 47447.2647
    S5 = 226.1030244:            S6 = 1#
    If X < 8# Then
        y# = X ^ 2
        AAA# = R1 + y * (R2 + y * (R3 + y * (R4 + y * (R5 + y * R6))))
        BBB# = S1 + y * (S2 + y * (S3 + y * (S4 + y * (S5 + y * S6))))
        BESSY0 = AAA# / BBB# + 0.636619772 * BESSJ0(X) * Log(X)
    Else
        Z = 8# / X
        y# = Z ^ 2
        XX = X - 0.785398164
        AAA# = Sqr(0.636619772 / X)
        BBB# = P1 + y * (P2 + y * (P3 + y * (P4 + y * P5)))
        CCC# = Q1 + y * (Q2 + y * (Q3 + y * (Q4 + y * Q5)))
        BESSY0 = AAA# * (Sin(XX) * BBB# + Z * Cos(XX) * CCC#)
    End If
End Function