> S := { 2, 3, 5, 7, 11, Pi, "foo", { 2/3, 3/4, 4/5 } };
           S := {2, 3, 5, 7, 11, "foo", Pi, {2/3, 3/4, 4/5}}

> type( S, set );
                                  true

> Pi in S;
          Pi  in  {2, 3, 5, 7, 11, "foo", Pi, {2/3, 3/4, 4/5}}

> if Pi in S then print( yes ) else print( no ) end:
                                  yes

> member( Pi, S );
                                  true

> if 4 in S then print( yes ) else print( no ) end:
                                   no

> evalb( { 2/3, 3/4, 4/5 } in S );
                                  true

> { a, b, c } union { 1, 2, 3 };
                           {1, 2, 3, a, b, c}

> { a, b, c } intersect { b, c, d };
                                 {b, c}

> { a, b, c } minus { b, c, d };
                                  {a}

> { a, b } subset { a, b, c };
                                  true

> { a, d } subset { a, b, c };
                                 false

> evalb( { 1, 2, 3 } = { 1, 2, 3 } );
                                  true

> evalb( { 1, 2, 3 } = { 1, 2, 4 } );
                                 false