Dear Robert,

thank you very much for your reply. Now it works great. :)

Best regards,

nvx

Dear Axel,

thank you for your reply. The problem was, as usual, "between the chair and the keyboard." ;) I was declaring the function incorrectly (Lf(q):=q->piecewise(...); instead of Lf:=q->piecewise(...);).

Have a nice day.

nvx

Never mind, now I see the mistake I made...