fact: Parameter size_add : forall u p1 p2, size (add u p1 p2) = maxn (size p1) (size p2).
imports: Coq(ZArith Reals) Coquelicot(Coquelicot) mathcomp.ssreflect(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype bigop) Flocq(Core) Stdlib MathComp Interval Xreal Basic_rec