d=CELDIM(I)
[Cell dimension.  I is the cell index of a cell c of a cylindrical
algebraic decomposition of @E sup r@ for some r>=1.  d is the
dimension of c.]
     safe r,i,k,I'.
(1)  d=0;  r=LENGTH(I);  I'=I;  for i=1,...,r do
     { ADV(I';k,I');  d=d+ODD(k) };  return..