# dbsi0e.f

          DOUBLE PRECISION FUNCTION DBSI0E (X)
    C***BEGIN PROLOGUE  DBSI0E
    C***PURPOSE  Compute the exponentially scaled modified (hyperbolic)
    C            Bessel function of the first kind of order zero.
    C***LIBRARY   SLATEC (FNLIB)
    C***CATEGORY  C10B1
    C***TYPE      DOUBLE PRECISION (BESI0E-S, DBSI0E-D)
    C***KEYWORDS  EXPONENTIALLY SCALED, FIRST KIND, FNLIB,
    C             HYPERBOLIC BESSEL FUNCTION, MODIFIED BESSEL FUNCTION,
    C             ORDER ZERO, SPECIAL FUNCTIONS
    C***AUTHOR  Fullerton, W., (LANL)
    C***DESCRIPTION
    C
    C DBSI0E(X) calculates the double precision exponentially scaled
    C modified (hyperbolic) Bessel function of the first kind of order
    C zero for double precision argument X.  The result is the Bessel
    C function I0(X) multiplied by EXP(-ABS(X)).
    C
    C Series for BI0        on the interval  0.          to  9.00000E+00
    C                                        with weighted error   9.51E-34
    C                                         log weighted error  33.02
    C                               significant figures required  33.31
    C                                    decimal places required  33.65
    C
    C Series for AI0        on the interval  1.25000E-01 to  3.33333E-01
    C                                        with weighted error   2.74E-32
    C                                         log weighted error  31.56
    C                               significant figures required  30.15
    C                                    decimal places required  32.39
    C
    C Series for AI02       on the interval  0.          to  1.25000E-01
    C                                        with weighted error   1.97E-32
    C                                         log weighted error  31.71
    C                               significant figures required  30.15
    C                                    decimal places required  32.63
    C
    C***REFERENCES  (NONE)
    C***ROUTINES CALLED  D1MACH, DCSEVL, INITDS
    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***END PROLOGUE  DBSI0E