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4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.tcs.unibo.it *)
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15 include "ground_2/relocation/nstream_lift.ma".
17 (* RELOCATION N-STREAM ******************************************************)
19 coinductive sle: relation rtmap ≝
20 | sle_next: ∀f1,f2,g1,g2. sle f1 f2 → g1 = ↑f1 → g2 = ↑f2 → sle g1 g2
21 | sle_push: ∀f1,f2,g1,g2. sle f1 f2 → g1 = ⫯f1 → g2 = ⫯f2 → sle g1 g2
22 | sle_weak: ∀f1,f2,g1,g2. sle f1 f2 → g1 = ↑f1 → g2 = ⫯f2 → sle g1 g2
25 interpretation "inclusion (nstream)"
26 'subseteq t1 t2 = (sle t1 t2).
28 (* Basic inversion lemmas ***************************************************)
30 fact sle_inv_xO_aux: ∀g1,g2. g1 ⊆ g2 → ∀f2. g2 = ↑f2 →
31 ∃∃f1. f1 ⊆ f2 & g1 = ↑f1.
33 #f1 #f2 #g1 #g2 #H #H1 #H2 #x2 #Hx2 destruct
34 [ lapply (injective_push … Hx2) -Hx2 /2 width=3 by ex2_intro/ ]
35 elim (discr_next_push … Hx2)
38 lemma sle_inv_xO: ∀g1,f2. g1 ⊆ ↑f2 → ∃∃f1. f1 ⊆ f2 & g1 = ↑f1.
39 /2 width=3 by sle_inv_xO_aux/ qed-.
41 fact sle_inv_Sx_aux: ∀g1,g2. g1 ⊆ g2 → ∀f1. g1 = ⫯f1 →
42 ∃∃f2. f1 ⊆ f2 & g2 = ⫯f2.
44 #f1 #f2 #g1 #g2 #H #H1 #H2 #x1 #Hx1 destruct
45 [2: lapply (injective_next … Hx1) -Hx1 /2 width=3 by ex2_intro/ ]
46 elim (discr_push_next … Hx1)
49 lemma sle_inv_Sx: ∀f1,g2. ⫯f1 ⊆ g2 → ∃∃f2. f1 ⊆ f2 & g2 = ⫯f2.
50 /2 width=3 by sle_inv_Sx_aux/ qed-.
52 fact sle_inv_OS_aux: ∀g1,g2. g1 ⊆ g2 → ∀f1,f2. g1 = ↑f1 → g2 = ⫯f2 → f1 ⊆ f2.
54 #f1 #f2 #g1 #g2 #H #H1 #H2 #x1 #x2 #Hx1 #Hx2 destruct
55 [ elim (discr_push_next … Hx2)
56 | elim (discr_next_push … Hx1)
57 | lapply (injective_push … Hx1) -Hx1
58 lapply (injective_next … Hx2) -Hx2 //
62 lemma sle_inv_OS: ∀f1,f2. ↑f1 ⊆ ⫯f2 → f1 ⊆ f2.
63 /2 width=5 by sle_inv_OS_aux/ qed-.
65 (* Advanced inversion lemmas ************************************************)
67 fact sle_inv_OO_aux: ∀g1,g2. g1 ⊆ g2 → ∀f1,f2. g1 = ↑f1 → g2 = ↑f2 → f1 ⊆ f2.
68 #g1 #g2 #H #f1 #f2 #H1 #H2 elim (sle_inv_xO_aux … H … H2) -g2
69 #x1 #H #Hx1 destruct lapply (injective_push … Hx1) -Hx1 //
72 fact sle_inv_SS_aux: ∀g1,g2. g1 ⊆ g2 → ∀f1,f2. g1 = ⫯f1 → g2 = ⫯f2 → f1 ⊆ f2.
73 #g1 #g2 #H #f1 #f2 #H1 #H2 elim (sle_inv_Sx_aux … H … H1) -g1
74 #x2 #H #Hx2 destruct lapply (injective_next … Hx2) -Hx2 //