End hlist_rel_map.

(* Specifications: *)
Theorem hlist_hrel_equiv
: forall T (F : T -> Type) (R : forall t, F t -> F t -> Prop) ls (h h' : hlist F ls),
hlist_hrel R h h' ->
equiv_hlist R h h'.
Theorem hlist_hrel_flip
: forall T (F G : T -> Type) (R : forall t, F t -> G t -> Prop) ls
(h : hlist F ls) (h' : hlist G ls),
hlist_hrel R h h' ->
hlist_hrel (fun t a b => R t b a) h' h.