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..