      \fitem{dim}{(t:tab \emph{or} n:nim)}: if the argument is a tab
      \code{t}, it returns the dimension \code{t}, i.e. the maximal number
      of nested tabs. If the argument is a nim \code{n}, it returns the
      number of elements in the tab returned by the application of the
      nim. In either case, the returned value is an integer strictly
      greater than 0. If the argument is not a tab nor a nim, the
      dimension is~0.



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

