matita/matita/contribs/lambda_delta/Basic_2/reducibility/tnf.ma

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  14
  15 include "Basic_2/substitution/tps_lift.ma".
  16 include "Basic_2/reducibility/trf.ma".
  17 include "Basic_2/reducibility/tpr.ma".
  18
  19 (* CONTEXT-FREE NORMAL TERMS ************************************************)
  20
  21 definition tnf: term → Prop ≝
  22    NF … tpr (eq …).
  23
  24 interpretation
  25    "context-free normality (term)"
  26    'Normal T = (tnf T).
  27
  28 (* Basic inversion lemmas ***************************************************)
  29
  30 lemma tnf_inv_abst: ∀V,T. ℕ[𝕔{Abst}V.T] → ℕ[V] ∧ ℕ[T].
  31 #V1 #T1 #HVT1 @conj
  32 [ #V2 #HV2 lapply (HVT1 (𝕔{Abst}V2.T1) ?) -HVT1 /2/ -HV2 #H destruct -V1 T1 //
  33 | #T2 #HT2 lapply (HVT1 (𝕔{Abst}V1.T2) ?) -HVT1 /2/ -HT2 #H destruct -V1 T1 //
  34 ]
  35 qed.
  36
  37 lemma tnf_inv_appl: ∀V,T. ℕ[𝕔{Appl}V.T] → ∧∧ ℕ[V] & ℕ[T] & 𝕊[T].
  38 #V1 #T1 #HVT1 @and3_intro
  39 [ #V2 #HV2 lapply (HVT1 (𝕔{Appl}V2.T1) ?) -HVT1 /2/ -HV2 #H destruct -V1 T1 //
  40 | #T2 #HT2 lapply (HVT1 (𝕔{Appl}V1.T2) ?) -HVT1 /2/ -HT2 #H destruct -V1 T1 //
  41 | generalize in match HVT1 -HVT1; elim T1 -T1 * // * #W1 #U1 #_ #_ #H
  42   [ elim (lift_total V1 0 1) #V2 #HV12
  43     lapply (H (𝕔{Abbr}W1.𝕔{Appl}V2.U1) ?) -H /2/ -HV12 #H destruct
  44   | lapply (H (𝕔{Abbr}V1.U1) ?) -H /2/ #H destruct
  45 ]
  46 qed.
  47
  48 axiom tnf_inv_abbr: ∀V,T. ℕ[𝕔{Abbr}V.T] → False.
  49
  50 lemma tnf_inv_cast: ∀V,T. ℕ[𝕔{Cast}V.T] → False.
  51 #V #T #H lapply (H T ?) -H /2/
  52 qed.
  53
  54 (* Basic properties *********************************************************)
  55
  56 lemma tpr_tif_eq: ∀T1,T2. T1 ⇒ T2 →  𝕀[T1] → T1 = T2.
  57 #T1 #T2 #H elim H -T1 T2
  58 [ //
  59 | * #V1 #V2 #T1 #T2 #_ #_ #IHV1 #IHT1 #H
  60   [ elim (tif_inv_appl … H) -H #HV1 #HT1 #_
  61     >IHV1 -IHV1 // -HV1 >IHT1 -IHT1 //
  62   | elim (tif_inv_cast … H)
  63   ]
  64 | #V1 #V2 #W #T1 #T2 #_ #_ #_ #_ #H
  65   elim (tif_inv_appl … H) -H #_ #_ #H
  66   elim (simple_inv_bind … H)
  67 | * #V1 #V2 #T1 #T #T2 #_ #_ #HT2 #IHV1 #IHT1 #H
  68   [ -HT2 IHV1 IHT1; elim (tif_inv_abbr … H)
  69   | <(tps_inv_refl_SO2 … HT2 ?) -HT2 //
  70     elim (tif_inv_abst … H) -H #HV1 #HT1
  71     >IHV1 -IHV1 // -HV1 >IHT1 -IHT1 //
  72   ]
  73 | #V #V1 #V2 #W1 #W2 #T1 #T2 #_ #_ #_ #_ #_ #_ #_ #H
  74   elim (tif_inv_appl … H) -H #_ #_ #H
  75   elim (simple_inv_bind … H)
  76 | #V1 #T1 #T2 #T #_ #_ #_ #H
  77   elim (tif_inv_abbr … H)
  78 | #V1 #T1 #T #_ #_ #H
  79   elim (tif_inv_cast … H)
  80 ]
  81 qed.
  82
  83 theorem tif_tnf: ∀T1.  𝕀[T1] → ℕ[T1].
  84 /2/ qed.
  85
  86 (* Note: this property is unusual *)
  87 theorem tnf_trf_false: ∀T1. ℝ[T1] → ℕ[T1] → False.
  88 #T1 #H elim H -T1
  89 [ #V #T #_ #IHV #H elim (tnf_inv_abst … H) -H /2/
  90 | #V #T #_ #IHT #H elim (tnf_inv_abst … H) -H /2/
  91 | #V #T #_ #IHV #H elim (tnf_inv_appl … H) -H /2/
  92 | #V #T #_ #IHV #H elim (tnf_inv_appl … H) -H /2/
  93 | #V #T #H elim (tnf_inv_abbr … H)
  94 | #V #T #H elim (tnf_inv_cast … H)
  95 | #V #W #T #H elim (tnf_inv_appl … H) -H #_ #_ #H
  96   elim (simple_inv_bind … H)
  97 ]
  98 qed.
  99
 100 theorem tnf_tif: ∀T1. ℕ[T1] → 𝕀[T1].
 101 /2/ qed.
 102
 103 lemma tnf_abst: ∀V,T. ℕ[V] → ℕ[T] → ℕ[𝕔{Abst}V.T].
 104 /4 width=1/ qed.
 105
 106 lemma tnf_appl: ∀V,T. ℕ[V] → ℕ[T] → 𝕊[T] → ℕ[𝕔{Appl}V.T].
 107 /4 width=1/ qed.