asyjy.f
SUBROUTINE ASYJY (FUNJY, X, FNU, FLGJY, IN, Y, WK, IFLW)
C***BEGIN PROLOGUE ASYJY
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Warning: this routine is not intended to be user-callable.
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C***SUBSIDIARY
C***PURPOSE Subsidiary to BESJ and BESY
C***LIBRARY SLATEC
C***TYPE SINGLE PRECISION (ASYJY-S, DASYJY-D)
C***AUTHOR Amos, D. E., (SNLA)
C***DESCRIPTION
C
C ASYJY computes Bessel functions J and Y
C for arguments X.GT.0.0 and orders FNU.GE.35.0
C on FLGJY = 1 and FLGJY = -1 respectively
C
C INPUT
C
C FUNJY - external function JAIRY or YAIRY
C X - argument, X.GT.0.0E0
C FNU - order of the first Bessel function
C FLGJY - selection flag
C FLGJY = 1.0E0 gives the J function
C FLGJY = -1.0E0 gives the Y function
C IN - number of functions desired, IN = 1 or 2
C
C OUTPUT
C
C Y - a vector whose first in components contain the sequence
C IFLW - a flag indicating underflow or overflow
C return variables for BESJ only
C WK(1) = 1 - (X/FNU)**2 = W**2
C WK(2) = SQRT(ABS(WK(1)))
C WK(3) = ABS(WK(2) - ATAN(WK(2))) or
C ABS(LN((1 + WK(2))/(X/FNU)) - WK(2))
C = ABS((2/3)*ZETA**(3/2))
C WK(4) = FNU*WK(3)
C WK(5) = (1.5*WK(3)*FNU)**(1/3) = SQRT(ZETA)*FNU**(1/3)
C WK(6) = SIGN(1.,W**2)*WK(5)**2 = SIGN(1.,W**2)*ZETA*FNU**(2/3)
C WK(7) = FNU**(1/3)
C
C Abstract
C ASYJY implements the uniform asymptotic expansion of
C the J and Y Bessel functions for FNU.GE.35 and real
C X.GT.0.0E0. The forms are identical except for a change
C in sign of some of the terms. This change in sign is
C accomplished by means of the flag FLGJY = 1 or -1. On
C FLGJY = 1 the AIRY functions AI(X) and DAI(X) are
C supplied by the external function JAIRY, and on
C FLGJY = -1 the AIRY functions BI(X) and DBI(X) are
C supplied by the external function YAIRY.
C
C***SEE ALSO BESJ, BESY
C***ROUTINES CALLED I1MACH, R1MACH
C***REVISION HISTORY (YYMMDD)
C 750101 DATE WRITTEN
C 890531 Changed all specific intrinsics to generic. (WRB)
C 891009 Removed unreferenced variable. (WRB)
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 900328 Added TYPE section. (WRB)
C 910408 Updated the AUTHOR section. (WRB)
C***END PROLOGUE ASYJY