#[global]
Hint Resolve lel_refl lel_cons_cons lel_cons lel_nil lel_nil nil_cons:
datatypes.
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(** ** Set inclusion on list  *)
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Section SetIncl.
Variable A : Type.
Definition incl (l m:list A) := forall a:A, In a l -> In a m.
#[local]
Hint Unfold incl : core.

Lemma incl_tran : forall l m n:list A, incl l m -> incl m n -> incl l n.