VML for safe evaluation of function

Hello,

         I plan to use VML to evalaute the following functions:

y = x / (exp(x) - 1)   and dy/dx =  1/(exp(x)-1)  - x exp(x)/(exp(x)-1)^2

I have to make sure that, i do not get NAN or Infinity at x =0 or x << 1

Any suggestions on how to write the subroutine.

for y i use, expm1 and code works fine i.e, limit x->0 y = 1

using expm1 in dy/dx i am getting, infinity for small x  say 1D-20.

Thanks

Reddy