fact: Fixpoint add P Q := match P with | Pconst c => addC c Q | PX P1 v P2 => add_aux (add P1) P1 v (add P2 Q) end.
imports: HoTT.Classes.interfaces.abstract_algebra HoTT.Classes.theory.additional_operations HoTT.Classes.tactics.ring_quote HoTT.Classes.theory.rings