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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 "lambda/types.ma".
16 include "lambda/lambda_notation.ma".
18 (* MATTER CONCERNING STRONG NORMALIZATION TO BE PUT ELSEWHERE *****************)
20 (* arithmetics ****************************************************************)
22 theorem arith1: ∀x,y. (S x) ≰ (S y) → x ≰ y.
23 #x #y #HS @nmk (elim HS) -HS /3/
26 theorem arith2: ∀i,p,k. k ≤ i → i + p - (k + p) = i - k.
27 #i #p #k #H @plus_to_minus
28 >commutative_plus >(commutative_plus k) >associative_plus @eq_f /2/
31 theorem arith3: ∀x,y,z. x ≰ y → x + z ≰ y + z.
32 #x #y #z #H @nmk (elim H) -H /3/
35 theorem arith4: ∀x,y. S x ≰ y → x≠y → y < x.
36 #x #y #H1 #H2 lapply (not_le_to_lt … H1) -H1 #H1 @not_eq_to_le_to_lt /2/
39 theorem arith5: ∀x,y. x < y → S (y - 1) ≰ x.
40 #x #y #H @lt_to_not_le <minus_Sn_m /2/
43 (* lists **********************************************************************)
45 (* all(P,l) holds when P holds for all members of l *)
46 let rec all (A:Type[0]) (P:A→Prop) l on l ≝ match l with
48 | cons hd tl ⇒ P hd ∧ all A P tl
51 theorem all_append: ∀A,P,l2,l1. all A P l1 → all A P l2 → all A P (l1 @ l2).
52 #A #P #l2 #l1 (elim l1) -l1 (normalize) // #hd #tl #IH1 #H (elim H) /3/
55 (* all(?,P,l1,l2) holds when P holds for all paired members of l1 and l2 *)
56 let rec all2 (A:Type[0]) (P:A→A→Prop) l1 l2 on l1 ≝ match l1 with
58 | cons hd1 tl1 ⇒ match l2 with
60 | cons hd2 tl2 ⇒ P hd1 hd2 ∧ all2 A P tl1 tl2
64 theorem length_append: ∀A. ∀(l2,l1:list A). |l1@l2| = |l1| + |l2|.
65 #A #l2 #l1 (elim l1) -l1 (normalize) //
68 (* terms **********************************************************************)
70 (* Appl F l generalizes App applying F to a list of arguments
71 * The head of l is applied first
73 let rec Appl F l on l ≝ match l with
75 | cons A D ⇒ Appl (App F A) D
78 theorem appl_append: ∀N,l,M. Appl M (l @ [N]) = App (Appl M l) N.
79 #N #l (elim l) -l // #hd #tl #IHl #M >IHl //
82 (* FG: not needed for now
84 inductive neutral: T → Prop ≝
85 | neutral_sort: ∀n.neutral (Sort n)
86 | neutral_rel: ∀i.neutral (Rel i)
87 | neutral_app: ∀M,N.neutral (App M N)
91 (* substitution ***************************************************************)
93 (* FG: do we need this?
94 definition lift0 ≝ λp,k,M . lift M p k. (**) (* remove definition *)
96 theorem lift_appl: ∀p,k,l,F. lift (Appl F l) p k =
97 Appl (lift F p k) (map … (lift0 p k) l).
98 #p #k #l (elim l) -l /2/ #A #D #IHl #F >IHl //
102 theorem lift_rel_lt: ∀i,p,k. (S i) ≤ k → lift (Rel i) k p = Rel i.
103 #i #p #k #Hik normalize >(le_to_leb_true … Hik) //
106 theorem lift_rel_ge: ∀i,p,k. (S i) ≰ k → lift (Rel i) k p = Rel (i+p).
107 #i #p #k #Hik normalize >(lt_to_leb_false (S i) k) /2/
110 theorem lift_app: ∀M,N,k,p.
111 lift (App M N) k p = App (lift M k p) (lift N k p).
114 theorem lift_lambda: ∀N,M,k,p. lift (Lambda N M) k p =
115 Lambda (lift N k p) (lift M (k + 1) p).
118 theorem lift_prod: ∀N,M,k,p.
119 lift (Prod N M) k p = Prod (lift N k p) (lift M (k + 1) p).
122 theorem subst_app: ∀M,N,k,L. (App M N)[k≝L] = App M[k≝L] N[k≝L].
125 theorem subst_lambda: ∀N,M,k,L. (Lambda N M)[k≝L] = Lambda N[k≝L] M[k+1≝L].
128 theorem subst_prod: ∀N,M,k,L. (Prod N M)[k≝L] = Prod N[k≝L] M[k+1≝L].
131 (* telescopic delifting substitution of l in M.
132 * Rel 0 is replaced with the head of l
134 let rec tsubst M l on l ≝ match l with
136 | cons A D ⇒ (tsubst M[0≝A] D)
139 interpretation "telescopic substitution" 'Subst1 M l = (tsubst M l).
141 theorem tsubst_refl: ∀l,t. (lift t 0 (|l|))[l] = t.
142 #l (elim l) -l (normalize) // #hd #tl #IHl #t cut (S (|tl|) = |tl| + 1) // (**) (* eliminate cut *)
145 theorem tsubst_sort: ∀n,l. (Sort n)[l] = Sort n.