matita/matita/contribs/lambdadelta/basic_2/reduction/chnf.ma

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  14
  15 include "basic_2/reduction/cpr_tshf.ma".
  16
  17 (* CONTEXT-SENSITIVE WEAK HEAD NORMAL TERMS *********************************)
  18
  19 definition chnf: lenv → predicate term ≝ λL. NF … (cpr L) tshf.
  20
  21 interpretation
  22    "context-sensitive head normality (term)"
  23    'HdNormal L T = (chnf L T).
  24
  25 (* Basic inversion lemmas ***************************************************)
  26
  27 lemma chnf_inv_tshf: ∀L,T. L ⊢ 𝐇𝐍⦃T⦄ → T ≈ T.
  28 normalize /2 width=1/
  29 qed-.
  30
  31 (* Basic properties *********************************************************)
  32
  33 lemma tshf_thnf: ∀T. T ≈ T → ⋆ ⊢ 𝐇𝐍⦃T⦄.
  34 #T #HT #T2 #H elim (cpr_fwd_tshf1 … H) -H //
  35 #H elim H //
  36 qed.