DOUBLE PRECISION FUNCTION DEXPRL(X)
C***BEGIN PROLOGUE  DEXPRL
C***DATE WRITTEN   770801   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  C4B
C***KEYWORDS  DOUBLE PRECISION,ELEMENTARY FUNCTION,EXPONENTIAL,
C             FIRST ORDER,RELATIVE ACCURACY
C***AUTHOR  FULLERTON, W., (LANL)
C***PURPOSE  Calculates the d.p. relative error exponential
C            (DEXP(X)-1)/X.
C***DESCRIPTION
C
C Evaluate  EXPREL(X) = (EXP(X) - 1.0) / X.   For small ABS(X) the
C Taylor series is used.  If X is negative the reflection formula
C         EXPREL(X) = EXP(X) * EXPREL(ABS(X))
C may be used.  This reflection formula will be of use when the
C evaluation for small ABS(X) is done by Chebyshev series rather than
C Taylor series.
C***REFERENCES  (NONE)
C***ROUTINES CALLED  D1MACH
C***END PROLOGUE  DEXPRL