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4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
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15 include "basic_2/static/lfeq.ma".
16 include "basic_2/static/lfxs_lfxs.ma".
17 include "basic_2/i_static/tc_lfxs_fqup.ma".
20 axiom cext2_inv_LTC: ∀R,L,I1,I2. cext2 (LTC … R) L I1 I2 → LTC … (cext2 R) L I1 I2.
22 #R #L #I1 #I2 * -I1 -I2
23 [ /2 width=1 by ext2_unit, inj/
29 lemma pippo: ∀RN,RP. (∀L. reflexive … (RP L)) →
30 ∀f,L1,L2. L1 ⪤*[LTC … RN, RP, f] L2 →
31 TC … (lexs RN RP f) L1 L2.
32 #RN #RP #HRP #f #L1 #L2 #H elim H -f -L1 -L2
33 [ /2 width=1 by lexs_atom, inj/ ]
34 #f #I1 #I2 #L1 #L2 #HL12 #HI12 #IH
39 axiom lexs_frees_confluent_LTC_sn: ∀RN,RP. lexs_frees_confluent RN RP →
40 lexs_frees_confluent (LTC … RN) RP.
42 #RN #RP #HR #f1 #L1 #T #Hf1 #L2 #H
44 (* ITERATED EXTENSION ON REFERRED ENTRIES OF A CONTEXT-SENSITIVE REALTION ***)
46 lemma pippo: ∀R. (∀L. reflexive … (R L)) →
47 (lexs_frees_confluent (cext2 R) cfull) →
48 ∀L1,L2,T. L1 ⪤**[R, T] L2 →
49 ∃∃L. L1 ⪤*[LTC … R, T] L & L ≡[T] L2.
50 #R #H1R #H2R #L1 #L2 #T #H
51 @(tc_lfxs_ind_sn … H1R … H) -H -L2
52 [ /4 width=5 by lfxs_refl, inj, ex2_intro/
53 | #L0 #L2 #_ #HL02 * #L * #f1 #Hf1 #HL1 #HL0
54 lapply (lexs_co ??? cfull … (cext2_inv_LTC R) … HL1) -HL1 // #HL1
55 lapply (lfeq_lfxs_trans … HL0 … HL02) -L0 #HL2
56 elim (lexs_frees_confluent_LTC_sn … H2R … Hf1 … HL1) #f2 #Hf2 #Hf21
57 lapply (lfxs_inv_frees … HL2 … Hf2) -HL2 #HL2
58 elim (lexs_sle_split … ceq_ext … HL2 … Hf21) -HL2
60 |*: /2 width=1 by ext2_refl/
62 lapply (sle_lexs_trans … HL0 … Hf21) -Hf21 // #H
63 elim (H2R … Hf2 … H) -H #f0 #Hf0 #Hf02
64 lapply (sle_lexs_trans … HL02 … Hf02) -f2 // #HL02
67 | @(ex2_intro … HL02) //