matita/matita/contribs/lambda_delta/Basic_2/grammar/lsubs.ma

   1 (**************************************************************************)
   2 (*       ___                                                              *)
   3 (*      ||M||                                                             *)
   4 (*      ||A||       A project by Andrea Asperti                           *)
   5 (*      ||T||                                                             *)
   6 (*      ||I||       Developers:                                           *)
   7 (*      ||T||         The HELM team.                                      *)
   8 (*      ||A||         http://helm.cs.unibo.it                             *)
   9 (*      \   /                                                             *)
  10 (*       \ /        This file is distributed under the terms of the       *)
  11 (*        v         GNU General Public License Version 2                  *)
  12 (*                                                                        *)
  13 (**************************************************************************)
  14
  15 include "Basic_2/grammar/lenv_length.ma".
  16
  17 (* LOCAL ENVIRONMENT REFINEMENT FOR SUBSTITUTION ****************************)
  18
  19 inductive lsubs: nat → nat → relation lenv ≝
  20 | lsubs_sort: ∀d,e. lsubs d e (⋆) (⋆)
  21 | lsubs_OO:   ∀L1,L2. lsubs 0 0 L1 L2
  22 | lsubs_abbr: ∀L1,L2,V,e. lsubs 0 e L1 L2 →
  23               lsubs 0 (e + 1) (L1. ⓓV) (L2.ⓓV)
  24 | lsubs_abst: ∀L1,L2,I,V1,V2,e. lsubs 0 e L1 L2 →
  25               lsubs 0 (e + 1) (L1. ⓛV1) (L2.ⓑ{I} V2)
  26 | lsubs_skip: ∀L1,L2,I1,I2,V1,V2,d,e.
  27               lsubs d e L1 L2 → lsubs (d + 1) e (L1. ⓑ{I1} V1) (L2. ⓑ{I2} V2)
  28 .
  29
  30 interpretation
  31   "local environment refinement (substitution)"
  32   'SubEq L1 d e L2 = (lsubs d e L1 L2).
  33
  34 definition lsubs_conf: ∀S. (lenv → relation S) → Prop ≝ λS,R.
  35                        ∀L1,s1,s2. R L1 s1 s2 →
  36                        ∀L2,d,e. L1 [d, e] ≼ L2 → R L2 s1 s2.
  37
  38 (* Basic properties *********************************************************)
  39
  40 lemma TC_lsubs_conf: ∀S,R. lsubs_conf S R → lsubs_conf S (λL. (TC … (R L))).
  41 #S #R #HR #L1 #s1 #s2 #H elim H -s2
  42 [ /3 width=5/
  43 | #s #s2 #_ #Hs2 #IHs1 #L2 #d #e #HL12
  44   lapply (HR … Hs2 … HL12) -HR -Hs2 -HL12 /3 width=3/
  45 ]
  46 qed.
  47
  48 lemma lsubs_bind_eq: ∀L1,L2,e. L1 [0, e] ≼ L2 → ∀I,V.
  49                      L1. ⓑ{I} V [0, e + 1] ≼ L2.ⓑ{I} V.
  50 #L1 #L2 #e #HL12 #I #V elim I -I /2 width=1/
  51 qed.
  52
  53 lemma lsubs_refl: ∀d,e,L. L [d, e] ≼ L.
  54 #d elim d -d
  55 [ #e elim e -e // #e #IHe #L elim L -L // /2 width=1/
  56 | #d #IHd #e #L elim L -L // /2 width=1/
  57 ]
  58 qed.
  59
  60 lemma lsubs_skip_lt: ∀L1,L2,d,e. L1 [d - 1, e] ≼ L2 → 0 < d →
  61                      ∀I1,I2,V1,V2. L1. ⓑ{I1} V1 [d, e] ≼ L2. ⓑ{I2} V2.
  62
  63 #L1 #L2 #d #e #HL12 #Hd >(plus_minus_m_m d 1) // /2 width=1/
  64 qed.
  65
  66 (* Basic inversion lemmas ***************************************************)
  67
  68 (* Basic forward lemmas ***************************************************)
  69
  70 fact lsubs_fwd_length_full1_aux: ∀L1,L2,d,e. L1 [d, e] ≼ L2 →
  71                                  d = 0 → e = |L1| → |L1| ≤ |L2|.
  72 #L1 #L2 #d #e #H elim H -L1 -L2 -d -e normalize
  73 [ //
  74 | /2 width=1/
  75 | /3 width=1/
  76 | /3 width=1/
  77 | #L1 #L2 #_ #_ #_ #_ #d #e #_ #_ >commutative_plus normalize #H destruct
  78 ]
  79 qed.
  80
  81 lemma lsubs_fwd_length_full1: ∀L1,L2. L1 [0, |L1|] ≼ L2 → |L1| ≤ |L2|.
  82 /2 width=5/ qed-.
  83
  84 fact lsubs_fwd_length_full2_aux: ∀L1,L2,d,e. L1 [d, e] ≼ L2 →
  85                                  d = 0 → e = |L2| → |L2| ≤ |L1|.
  86 #L1 #L2 #d #e #H elim H -L1 -L2 -d -e normalize
  87 [ //
  88 | /2 width=1/
  89 | /3 width=1/
  90 | /3 width=1/
  91 | #L1 #L2 #_ #_ #_ #_ #d #e #_ #_ >commutative_plus normalize #H destruct
  92 ]
  93 qed.
  94
  95 lemma lsubs_fwd_length_full2: ∀L1,L2. L1 [0, |L2|] ≼ L2 → |L2| ≤ |L1|.
  96 /2 width=5/ qed-.