bessj0.txt

常用的数值算法的VB程序

Function BESSJ0(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# = 57568490574#:        R2# = -13362590354#
    R3# = 651619640.7:         R4# = -11214424.18
    R5# = 77392.33017:         R6# = -184.9052456
    S1# = 57568490411#:        S2# = 1029532985#
    S3# = 9494680.718:         S4# = 59272.64853
    S5# = 267.8532712:         S6# = 1#
    If Abs(X) < 8# Then
       y# = X * X
       BBB# = y# * (R4# + y# * (R5# + y# * R6#))
       AAA# = R1# + y# * (R2# + y# * (R3# + BBB#))
       CCC# = y# * (S3# + y# * (S4# + y# * (S5# + y# * S6#)))
       BESSJ0 = AAA / (S1# + y# * (S2# + CCC#))
    Else
       AX# = Abs(X)
       Z# = 8# / AX#
       y# = Z# * Z#
       XX = AX# - 0.785398164
       CCC# = y# * (P3# + y# * (P4# + y# * P5#))
       AAA# = P1# + y# * (P2# + CCC#)
       DDD# = y# * (Q3# + y# * (Q4# + y# * Q5#))
       EEE# = Z# * Sin(XX) * (Q1# + y# * (Q2# + DDD#))
       BESSJ0 = Sqr(0.636619772 / AX#) * (Cos(XX) * AAA# - EEE#)
    End If
End Function