fact: Fixpoint vec_eq_dec_pos n (u v : vec n) { struct u } : (forall p, { vec_pos u p = vec_pos v p } + { vec_pos u p <> vec_pos v p }) -> { u = v } + { u <> v }.
imports: Arith Lia List Permutation Undecidability.Shared.Libs.DLW.Utils(utils) Undecidability.Shared.Libs.DLW.Vec(pos)