fact: Parameter nth_polyCons : forall a p k, nth (polyCons a p) k = if k is k'.+1 then nth p k' else a.
imports: Coq(ZArith Reals) Coquelicot(Coquelicot) mathcomp.ssreflect(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype bigop) Flocq(Core) Stdlib MathComp Interval Xreal Basic_rec