1 (**************************************************************************)
4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
10 (* \ / This file is distributed under the terms of the *)
11 (* v GNU General Public License Version 2 *)
13 (**************************************************************************)
15 include "ground/xoa/ex_3_1.ma".
16 include "delayed_updating/syntax/preterm.ma".
17 include "delayed_updating/notation/functions/pitchforkleftarrow_3.ma".
19 (* FOCALIZED SUBSTITUTION ***************************************************)
21 definition fsubst (p) (u): preterm → preterm ≝
23 ∨∨ ∃∃r. r ϵ u & p ϵ ▵t & p;;r = q
24 | ∧∧ q ϵ t & (∀r. p;;r = q → ⊥)
28 "focalized substitution (preterm)"
29 'PitchforkLeftArrow t p u = (fsubst p u t).