Please Gilles try a symbolic matrix [[ a, EE ],[ II, o ]]

The poly1 prefix before container [] is used to differentiate a list of a list of coefficients analogously to sets set[]

CAS author believe this feature to avoid the ambiguity between different data types, note that add polynomials of different dimensions zero adjustment is made to the left, while the right for lists

sym2poly(3*x^3+4*x^2+5*x+6) [ENTER] return poly[ 3, 4, 5, 6 ] that is different from [ 3, 4, 5, 6 ]

now string(Ans) "3,4,5,6" ??