# datanh.f

          DOUBLE PRECISION FUNCTION DATANH (X)
    C***BEGIN PROLOGUE  DATANH
    C***PURPOSE  Compute the arc hyperbolic tangent.
    C***LIBRARY   SLATEC (FNLIB)
    C***CATEGORY  C4C
    C***TYPE      DOUBLE PRECISION (ATANH-S, DATANH-D, CATANH-C)
    C***KEYWORDS  ARC HYPERBOLIC TANGENT, ATANH, ELEMENTARY FUNCTIONS,
    C             FNLIB, INVERSE HYPERBOLIC TANGENT
    C***AUTHOR  Fullerton, W., (LANL)
    C***DESCRIPTION
    C
    C DATANH(X) calculates the double precision arc hyperbolic
    C tangent for double precision argument X.
    C
    C Series for ATNH       on the interval  0.          to  2.50000E-01
    C                                        with weighted error   6.86E-32
    C                                         log weighted error  31.16
    C                               significant figures required  30.00
    C                                    decimal places required  31.88
    C
    C***REFERENCES  (NONE)
    C***ROUTINES CALLED  D1MACH, DCSEVL, INITDS, XERMSG
    C***REVISION HISTORY  (YYMMDD)
    C   770601  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  DATANH