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4 (* ||A|| A project by Andrea Asperti *)
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7 (* ||T|| The HELM team. *)
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15 include "delayed_updating/syntax/path_depth.ma".
16 include "delayed_updating/syntax/path_structure.ma".
17 include "delayed_updating/syntax/path_balanced.ma".
18 include "delayed_updating/substitution/fsubst.ma".
19 include "delayed_updating/notation/relations/black_rightarrow_df_4.ma".
21 (* DELAYED FOCUSED REDUCTION ************************************************)
23 inductive dfr (p) (q) (t): predicate preterm ≝
25 let r ≝ p●𝗔◗b●𝗟◗q◖𝗱❨↑❘q❘❩ in
26 r ϵ t → ⊓⊗b → dfr p q t (t[⋔r←t⋔(p◖𝗦)])
30 "focused balanced reduction with delayed updating (preterm)"
31 'BlackRightArrowDF t1 p q t2 = (dfr p q t1 t2).