# This function adds labels to vectors and matrices.  If `x' is a
# vector, then `id1' becomes its element labels.  If `x' is a matrix,
# then `id1' becomes its row labels and `id2' becomes its column
# labels.  If `x' has any other class, an exception is raised.

label = function (x; id1; id2)
{
  return self.(class(x)) (x; id1; id2);
};

( label.scalar =
  label.table =
  label.("function") =
  label.("NULL") =
    strip (function (x; id1; id2)
    {
      message ("run time error:  Invalid %s class for labels."; class(x));
      exception ();
    })
);

label.vector = strip (function (x; id1; id2)
{
  x.eid = id1;
  return x;
});

label.matrix = strip (function (x; id1; id2)
{
  x.rid = id1;
  x.cid = id2;
  return x;
});