matita/matita/contribs/lambdadelta/basic_2/etc_2A1/tshf/chnf.etc

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  14
  15 notation "hvbox( L ⊢ break 𝐇𝐍 ⦃ term 46 T ⦄ )"
  16    non associative with precedence 45
  17    for @{ 'HdNormal $L $T }.
  18
  19 include "basic_2/reduction/cpr_tshf.ma".
  20
  21 (* CONTEXT-SENSITIVE WEAK HEAD NORMAL TERMS *********************************)
  22
  23 definition chnf: lenv → predicate term ≝ λL. NF … (cpr L) tshf.
  24
  25 interpretation
  26    "context-sensitive head normality (term)"
  27    'HdNormal L T = (chnf L T).
  28
  29 (* Basic inversion lemmas ***************************************************)
  30
  31 lemma chnf_inv_tshf: ∀L,T. L ⊢ 𝐇𝐍⦃T⦄ → T ≈ T.
  32 normalize /2 width=1/
  33 qed-.
  34
  35 (* Basic properties *********************************************************)
  36
  37 lemma tshf_thnf: ∀T. T ≈ T → ⋆ ⊢ 𝐇𝐍⦃T⦄.
  38 #T #HT #T2 #H elim (cpr_fwd_tshf1 … H) -H //
  39 #H elim H //
  40 qed.