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4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
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15 include "delayed_updating/syntax/preterm.ma".
16 include "delayed_updating/substitution/lift.ma".
18 (* LIFT FOR PRETERM ***********************************************************)
20 definition lift_preterm (f) (t): preterm ≝
21 λp. ∃∃r. r ϵ t & p = ↑[f]r.
25 'UpArrow f t = (lift_preterm f t).