      \fitem{random}(), \vImpure: returns a random number between 0 and 1
      (included). The resolution of this random number generator is
      $\frac{1}{2^{31} - 1}$, which means that the minimal step between
      two numbers in the images of this function is $\frac{1}{2^{31} -
        1}$.  This is not a pure function because two successive calls are
      likely to return different results.


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

