complex function cexprl (z)
  c august 1980 edition.  w. fullerton, c3, los alamos scientific lab.
  c
  c evaluate  (cexp(z)-1)/z .  for small cabs(z), we use the taylor
  c series.  we could instead use the expression
  c        cexprl(z) = (exp(x)*exp(i*y)-1)/z
  c                  = (x*exprel(x) * (1 - 2*sin(y/2)**2) - 2*sin(y/2)**2
  c                                    + i*sin(y)*(1+x*exprel(x))) / z
  c
        complex z, cexp
        external  r1mach
        data nterms, rbnd, sqeps / 0, 2*0.0 /
  c
        if (nterms.ne.0) go to 10
        alneps = alog(r1mach(3))
        xn = 3.72 - 0.3*alneps
        xln = alog((xn+1.0)/1.36)
        nterms = xn - (xn*xln+alneps)/(xln+1.36) + 1.5
        rbnd = r1mach(3)
        sqeps = 0.0
  c
   10   r = cabs(z)
        if (r.le.0.5) go to 20
  c
        call entsrc (irold, 1)
        cexprl = (cexp(z) - 1.0) / z
        call erroff
        call entsrc (irold2, irold)
        if (abs(real(z)).lt.sqeps .and. cabs(cexprl).lt.sqeps) call
       1  seteru (41hcexprl  answer lt half prec, z near ni2pi,
       2  41, 1, 1)
        return
  c
   20   cexprl = (1.0, 0.0)
        if (r.lt.rbnd) return
  c
        cexprl = (0.0, 0.0)
        do 30 i=1,nterms
          cexprl = 1.0 + cexprl*z/float(nterms+2-i)
   30   continue
  c
        return
        end