double precision function dexprl (x)
c july 1980 edition.  w. fullerton, c3, los alamos scientific lab.
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
      double precision x, absx, alneps, xbnd, xln, xn,  d1mach,
     1  dexp, dlog
      external d1mach
      data nterms, xbnd / 0, 0.0d0 /
c
      if (nterms.ne.0) go to 10
      alneps = dlog(d1mach(3))
      xn = 3.72d0 - 0.3d0*alneps
      xln = dlog((xn+1.0d0)/1.36d0)
      nterms = xn - (xn*xln+alneps)/(xln+1.36d0) + 1.5d0
      xbnd = d1mach(3)
c
 10   absx = dabs(x)
      if (absx.le.0.5d0) go to 20
      call entsrc (irold, 1)
      dexprl = (dexp(x)-1.0d0)/x
      call entsrc (ir, irold)
      return
c
 20   dexprl = 1.0d0
      if (absx.lt.xbnd) return
c
      dexprl = 0.0d0
      do 30 i=1,nterms
        dexprl = 1.0d0 + dexprl*x/dble(float(nterms+2-i))
 30   continue
c
      return
      end