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(** Proofs of specification for functions defined over Vector  Author: Pierre Boutillier Institution: PPS, INRIA 12/2010 *)
Require Fin.
Definition cons_inj {A} {a1 a2} {n} {v1 v2 : t A n}
(eq : a1 :: v1 = a2 :: v2) : a1 = a2 /\ v1 = v2 :=
match eq in _ = x return caseS _ (fun a2' _ v2' => fun v1' => a1 = a2' /\ v1' = v2') x v1
with | eq_refl => conj eq_refl eq_refl
end.

Lemma take_idem : forall {A} p n (v:t A n)  le le',
take p le' (take p le v) = take p le v.