dasyik.f
SUBROUTINE DASYIK (X, FNU, KODE, FLGIK, RA, ARG, IN, Y)
C***BEGIN PROLOGUE DASYIK
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Warning: this routine is not intended to be user-callable.
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C***SUBSIDIARY
C***PURPOSE Subsidiary to DBESI and DBESK
C***LIBRARY SLATEC
C***TYPE DOUBLE PRECISION (ASYIK-S, DASYIK-D)
C***AUTHOR Amos, D. E., (SNLA)
C***DESCRIPTION
C
C DASYIK computes Bessel functions I and K
C for arguments X.GT.0.0 and orders FNU.GE.35
C on FLGIK = 1 and FLGIK = -1 respectively.
C
C INPUT
C
C X - Argument, X.GT.0.0D0
C FNU - Order of first Bessel function
C KODE - A parameter to indicate the scaling option
C KODE=1 returns Y(I)= I/SUB(FNU+I-1)/(X), I=1,IN
C or Y(I)= K/SUB(FNU+I-1)/(X), I=1,IN
C on FLGIK = 1.0D0 or FLGIK = -1.0D0
C KODE=2 returns Y(I)=EXP(-X)*I/SUB(FNU+I-1)/(X), I=1,IN
C or Y(I)=EXP( X)*K/SUB(FNU+I-1)/(X), I=1,IN
C on FLGIK = 1.0D0 or FLGIK = -1.0D0
C FLGIK - Selection parameter for I or K FUNCTION
C FLGIK = 1.0D0 gives the I function
C FLGIK = -1.0D0 gives the K function
C RA - SQRT(1.+Z*Z), Z=X/FNU
C ARG - Argument of the leading exponential
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
C Abstract **** A double precision routine ****
C DASYIK implements the uniform asymptotic expansion of
C the I and K Bessel functions for FNU.GE.35 and real
C X.GT.0.0D0. 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 FLGIK = 1 or -1.
C
C***SEE ALSO DBESI, DBESK
C***ROUTINES CALLED D1MACH
C***REVISION HISTORY (YYMMDD)
C 750101 DATE WRITTEN
C 890531 Changed all specific intrinsics to generic. (WRB)
C 890911 Removed unnecessary intrinsics. (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 DASYIK