fact: Fixpoint T12Tree (a: T1): GenTree.tree nat := if a is cons b n c then GenTree.Node n [:: T12Tree b; T12Tree c] else GenTree.Leaf 0.
imports: mathcomp(all_ssreflect zify) Coq(Logic.Eqdep_dec) hydras(DecPreOrder ON_Generic T1 E0) gaia_hydras(T1Bridge)