# dbesi1.f

          DOUBLE PRECISION FUNCTION DBESI1 (X)
    C***BEGIN PROLOGUE  DBESI1
    C***PURPOSE  Compute the modified (hyperbolic) Bessel function of the
    C            first kind of order one.
    C***LIBRARY   SLATEC (FNLIB)
    C***CATEGORY  C10B1
    C***TYPE      DOUBLE PRECISION (BESI1-S, DBESI1-D)
    C***KEYWORDS  FIRST KIND, FNLIB, HYPERBOLIC BESSEL FUNCTION,
    C             MODIFIED BESSEL FUNCTION, ORDER ONE, SPECIAL FUNCTIONS
    C***AUTHOR  Fullerton, W., (LANL)
    C***DESCRIPTION
    C
    C DBESI1(X) calculates the double precision modified (hyperbolic)
    C Bessel function of the first kind of order one and double precision
    C argument X.
    C
    C Series for BI1        on the interval  0.          to  9.00000E+00
    C                                        with weighted error   1.44E-32
    C                                         log weighted error  31.84
    C                               significant figures required  31.45
    C                                    decimal places required  32.46
    C
    C***REFERENCES  (NONE)
    C***ROUTINES CALLED  D1MACH, DBSI1E, DCSEVL, INITDS, XERMSG
    C***REVISION HISTORY  (YYMMDD)
    C   770701  DATE WRITTEN
    C   890531  Changed all specific intrinsics to generic.  (WRB)
    C   890531  REVISION DATE from Version 3.2
    C   891214  Prologue converted to Version 4.0 format.  (BAB)
    C   900315  CALLs to XERROR changed to CALLs to XERMSG.  (THJ)
    C***END PROLOGUE  DBESI1