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4 (* ||A|| A project by Andrea Asperti *)
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7 (* ||T|| The HELM team. *)
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15 include "basic_2/static/ssta.ma".
17 (* ITERATED STRATIFIED STATIC TYPE ASSIGNMENT FOR TERMS *********************)
19 inductive sstas (h:sh) (g:sd h) (L:lenv): relation term ≝
20 | sstas_refl: ∀T,U,l. ⦃h, L⦄ ⊢ T •[g, l] U → sstas h g L T T
21 | sstas_step: ∀T,U1,U2,l. ⦃h, L⦄ ⊢ T •[g, l+1] U1 → sstas h g L U1 U2 →
24 interpretation "iterated stratified static type assignment (term)"
25 'StaticTypeStar h g L T U = (sstas h g L T U).
27 (* Basic eliminators ********************************************************)
29 fact sstas_ind_alt_aux: ∀h,g,L,U2. ∀R:predicate term.
30 (∀T,l. ⦃h, L⦄ ⊢ U2 •[g , l] T → R U2) →
31 (∀T,U1,l. ⦃h, L⦄ ⊢ T •[g, l + 1] U1 →
32 ⦃h, L⦄ ⊢ U1 •* [g] U2 → R U1 → R T
34 ∀T,U. ⦃h, L⦄ ⊢ T •*[g] U → U = U2 → R T.
35 #h #g #L #U2 #R #H1 #H2 #T #U #H elim H -H -T -U /2 width=3/ /3 width=5/
38 lemma sstas_ind_alt: ∀h,g,L,U2. ∀R:predicate term.
39 (∀T,l. ⦃h, L⦄ ⊢ U2 •[g , l] T → R U2) →
40 (∀T,U1,l. ⦃h, L⦄ ⊢ T •[g, l + 1] U1 →
41 ⦃h, L⦄ ⊢ U1 •* [g] U2 → R U1 → R T
43 ∀T. ⦃h, L⦄ ⊢ T •*[g] U2 → R T.
44 /3 width=9 by sstas_ind_alt_aux/ qed-.
46 (* Basic inversion lemmas ***************************************************)
48 fact sstas_inv_bind1_aux: ∀h,g,L,T,U. ⦃h, L⦄ ⊢ T •*[g] U →
49 ∀a,J,X,Y. T = ⓑ{a,J}Y.X →
50 ∃∃Z. ⦃h, L.ⓑ{J}Y⦄ ⊢ X •*[g] Z & U = ⓑ{a,J}Y.Z.
51 #h #g #L #T #U #H @(sstas_ind_alt … H) -T
52 [ #U0 #l #HU0 #a #J #X #Y #H destruct
53 elim (ssta_inv_bind1 … HU0) -HU0 #X0 #HX0 #H destruct /3 width=3/
54 | #T0 #U0 #l #HTU0 #_ #IHU0 #a #J #X #Y #H destruct
55 elim (ssta_inv_bind1 … HTU0) -HTU0 #X0 #HX0 #H destruct
56 elim (IHU0 a J X0 Y …) -IHU0 // #X1 #HX01 #H destruct /3 width=4/
60 lemma sstas_inv_bind1: ∀h,g,a,J,L,Y,X,U. ⦃h, L⦄ ⊢ ⓑ{a,J}Y.X •*[g] U →
61 ∃∃Z. ⦃h, L.ⓑ{J}Y⦄ ⊢ X •*[g] Z & U = ⓑ{a,J}Y.Z.
62 /2 width=3 by sstas_inv_bind1_aux/ qed-.
64 fact sstas_inv_appl1_aux: ∀h,g,L,T,U. ⦃h, L⦄ ⊢ T •*[g] U → ∀X,Y. T = ⓐY.X →
65 ∃∃Z. ⦃h, L⦄ ⊢ X •*[g] Z & U = ⓐY.Z.
66 #h #g #L #T #U #H @(sstas_ind_alt … H) -T
67 [ #U0 #l #HU0 #X #Y #H destruct
68 elim (ssta_inv_appl1 … HU0) -HU0 #X0 #HX0 #H destruct /3 width=3/
69 | #T0 #U0 #l #HTU0 #_ #IHU0 #X #Y #H destruct
70 elim (ssta_inv_appl1 … HTU0) -HTU0 #X0 #HX0 #H destruct
71 elim (IHU0 X0 Y ?) -IHU0 // #X1 #HX01 #H destruct /3 width=4/
75 lemma sstas_inv_appl1: ∀h,g,L,Y,X,U. ⦃h, L⦄ ⊢ ⓐY.X •*[g] U →
76 ∃∃Z. ⦃h, L⦄ ⊢ X •*[g] Z & U = ⓐY.Z.
77 /2 width=3 by sstas_inv_appl1_aux/ qed-.
79 (* Basic forward lemmas *****************************************************)
81 lemma sstas_fwd_correct: ∀h,g,L,T,U. ⦃h, L⦄ ⊢ T •*[g] U →
82 ∃∃l,W. ⦃h, L⦄ ⊢ U •[g, l] W.
83 #h #g #L #T #U #H @(sstas_ind_alt … H) -T // /2 width=3/