      \fitem{rnd_normal}($\mu$:float, $\sigma$:float) returns a random
      generator that produces floating-point values according to a
      \emph{normal distribution} $P$:
      $$
      P(x | \mu, \sigma) = 
      \frac{1}{\sigma \sqrt{2 \pi}}
      e^{-\frac{(x - \mu)^2}{2 \sigma^2}}
      $$



      %%% -------------------------------------------------------

