matita/matita/contribs/lambda_delta/basic_2/unfold/ldrops.ma

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  14
  15 include "basic_2/substitution/ldrop.ma".
  16 include "basic_2/unfold/gr2_minus.ma".
  17 include "basic_2/unfold/lifts.ma".
  18
  19 (* GENERIC LOCAL ENVIRONMENT SLICING ****************************************)
  20
  21 inductive ldrops: list2 nat nat → relation lenv ≝
  22 | ldrops_nil : ∀L. ldrops ⟠ L L
  23 | ldrops_cons: ∀L1,L,L2,des,d,e.
  24                ldrops des L1 L → ⇩[d,e] L ≡ L2 → ldrops ({d, e} @ des) L1 L2
  25 .
  26
  27 interpretation "generic local environment slicing"
  28    'RDropStar des T1 T2 = (ldrops des T1 T2).
  29
  30 (* Basic inversion lemmas ***************************************************)
  31
  32 fact ldrops_inv_nil_aux: ∀L1,L2,des. ⇩*[des] L1 ≡ L2 → des = ⟠ → L1 = L2.
  33 #L1 #L2 #des * -L1 -L2 -des //
  34 #L1 #L #L2 #d #e #des #_ #_ #H destruct
  35 qed.
  36
  37 (* Basic_1: was: drop1_gen_pnil *)
  38 lemma ldrops_inv_nil: ∀L1,L2. ⇩*[⟠] L1 ≡ L2 → L1 = L2.
  39 /2 width=3/ qed-.
  40
  41 fact ldrops_inv_cons_aux: ∀L1,L2,des. ⇩*[des] L1 ≡ L2 →
  42                           ∀d,e,tl. des = {d, e} @ tl →
  43                           ∃∃L. ⇩*[tl] L1 ≡ L & ⇩[d, e] L ≡ L2.
  44 #L1 #L2 #des * -L1 -L2 -des
  45 [ #L #d #e #tl #H destruct
  46 | #L1 #L #L2 #des #d #e #HT1 #HT2 #hd #he #tl #H destruct
  47   /2 width=3/
  48 qed.
  49
  50 (* Basic_1: was: drop1_gen_pcons *)
  51 lemma ldrops_inv_cons: ∀L1,L2,d,e,des. ⇩*[{d, e} @ des] L1 ≡ L2 →
  52                        ∃∃L. ⇩*[des] L1 ≡ L & ⇩[d, e] L ≡ L2.
  53 /2 width=3/ qed-.
  54
  55 lemma ldrops_inv_skip2: ∀I,des,i,des2. des ▭ i ≡ des2 →
  56                         ∀L1,K2,V2. ⇩*[des2] L1 ≡ K2. ⓑ{I} V2 →
  57                         ∃∃K1,V1,des1. des + 1 ▭ i + 1 ≡ des1 + 1 &
  58                                       ⇩*[des1] K1 ≡ K2 &
  59                                       ⇧*[des1] V2 ≡ V1 &
  60                                       L1 = K1. ⓑ{I} V1.
  61 #I #des #i #des2 #H elim H -des -i -des2
  62 [ #i #L1 #K2 #V2 #H
  63   >(ldrops_inv_nil … H) -L1 /2 width=7/
  64 | #des #des2 #d #e #i #Hid #_ #IHdes2 #L1 #K2 #V2 #H
  65   elim (ldrops_inv_cons … H) -H #L #HL1 #H
  66   elim (ldrop_inv_skip2 … H ?) -H /2 width=1/ #K #V >minus_plus #HK2 #HV2 #H destruct
  67   elim (IHdes2 … HL1) -IHdes2 -HL1 #K1 #V1 #des1 #Hdes1 #HK1 #HV1 #X destruct
  68   @(ex4_3_intro … K1 V1 … ) // [3,4: /2 width=7/ | skip ]
  69   normalize >plus_minus // @minuss_lt // /2 width=1/ (**) (* explicit constructors, /3 width=1/ is a bit slow *)
  70 | #des #des2 #d #e #i #Hid #_ #IHdes2 #L1 #K2 #V2 #H
  71   elim (IHdes2 … H) -IHdes2 -H #K1 #V1 #des1 #Hdes1 #HK1 #HV1 #X destruct
  72   /4 width=7/
  73 ]
  74 qed-.
  75
  76 (* Basic properties *********************************************************)
  77
  78 (* Basic_1: was: drop1_skip_bind *)
  79 lemma ldrops_skip: ∀L1,L2,des. ⇩*[des] L1 ≡ L2 → ∀V1,V2. ⇧*[des] V2 ≡ V1 →
  80                    ∀I. ⇩*[des + 1] L1. ⓑ{I} V1 ≡ L2. ⓑ{I} V2.
  81 #L1 #L2 #des #H elim H -L1 -L2 -des
  82 [ #L #V1 #V2 #HV12 #I
  83   >(lifts_inv_nil … HV12) -HV12 //
  84 | #L1 #L #L2 #des #d #e #_ #HL2 #IHL #V1 #V2 #H #I
  85   elim (lifts_inv_cons … H) -H /3 width=5/
  86 ].
  87 qed.
  88
  89 (* Basic_1: removed theorems 1: drop1_getl_trans
  90 *)