matita/matita/contribs/lambdadelta/delayed_updating/reduction/dfr.ma

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  11 (*        v         GNU General Public License Version 2                  *)
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  14
  15 include "ground/xoa/ex_3_1.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 (*
  20 include "delayed_updating/notation/functions/pitchforkleftarrow_3.ma".
  21 *)
  22
  23 (* DELAYED FOCALIZED REDUCTION **********************************************)
  24
  25 inductive dfr (p) (q) (t): predicate preterm ≝
  26 | dfr_beta (b) (n):
  27   let r ≝ p;;(𝗔;b;;(𝗟;q,𝗱❨n❩)) in
  28   r ϵ t → ⊓⊗b → dfr p q t (t[⋔r←t⋔p,𝗦])
  29 .
  30 (*
  31 interpretation
  32   "focalized substitution (preterm)"
  33   'PitchforkLeftArrow t p u = (fsubst p u t).
  34 *)