Moved a list comparison function in the list file

[helm.git] / matita / matita / lib / basics / lists / list.ma

diff --git a/matita/matita/lib/basics/lists/list.ma b/matita/matita/lib/basics/lists/list.ma
index c1f6ab73840d9f89103025f391a3406859752a36..725f57135f42428760b67c42cdfa1b9e88d4b531 100644 (file)
--- a/matita/matita/lib/basics/lists/list.ma
+++ b/matita/matita/lib/basics/lists/list.ma
@@ -92,6 +92,24 @@ lemma cons_injective_r : ∀A.∀a1,a2:A.∀l1,l2.a1::l1 = a2::l2 → l1 = l2.
 #A #a1 #a2 #l1 #l2 #Heq destruct //
 qed.
 
+(* comparing lists *)
+
+lemma compare_append : ∀A,l1,l2,l3,l4. l1@l2 = l3@l4 → 
+∃l:list A.(l1 = l3@l ∧ l4=l@l2) ∨ (l3 = l1@l ∧ l2=l@l4).
+#A #l1 elim l1
+  [#l2 #l3 #l4 #Heq %{l3} %2 % // @Heq
+  |#a1 #tl1 #Hind #l2 #l3 cases l3
+    [#l4 #Heq %{(a1::tl1)} %1 % // @sym_eq @Heq 
+    |#a3 #tl3 #l4 normalize in ⊢ (%→?); #Heq cases (Hind l2 tl3 l4 ?)
+      [#l * * #Heq1 #Heq2 %{l}
+        [%1 % // >Heq1 >(cons_injective_l ????? Heq) //
+        |%2 % // >Heq1 >(cons_injective_l ????? Heq) //
+        ]
+      |@(cons_injective_r ????? Heq) 
+      ]
+    ]
+  ]
+qed.
 (**************************** iterators ******************************)
 
 let rec map (A,B:Type[0]) (f: A → B) (l:list A) on l: list B ≝
@@ -268,6 +286,32 @@ let rec mem A (a:A) (l:list A) on l ≝
   [ nil ⇒ False
   | cons hd tl ⇒ a=hd ∨ mem A a tl
   ]. 
+  
+lemma mem_append: ∀A,a,l1,l2.mem A a (l1@l2) →
+  mem ? a l1 ∨ mem ? a l2.
+#A #a #l1 elim l1 
+  [#l2 #mema %2 @mema
+  |#b #tl #Hind #l2 * 
+    [#eqab %1 %1 @eqab 
+    |#Hmema cases (Hind ? Hmema) -Hmema #Hmema [%1 %2 //|%2 //]
+    ]
+  ]
+qed.
+
+lemma mem_append_l1: ∀A,a,l1,l2.mem A a l1 → mem A a (l1@l2).
+#A #a #l1 #l2 elim l1
+  [whd in ⊢ (%→?); @False_ind
+  |#b #tl #Hind * [#eqab %1 @eqab |#Hmema %2 @Hind //]
+  ]
+qed.
+
+lemma mem_append_l2: ∀A,a,l1,l2.mem A a l2 → mem A a (l1@l2).
+#A #a #l1 #l2 elim l1 [//|#b #tl #Hind #Hmema %2 @Hind //]
+qed.
+
+lemma mem_single: ∀A,a,b. mem A a [b] → a=b.
+#A #a #b * // @False_ind
+qed.
 
 lemma mem_map: ∀A,B.∀f:A→B.∀l,b. 
   mem ? b (map … f l) → ∃a. mem ? a l ∧ f a = b.
@@ -419,12 +463,33 @@ lemma All_nth : ∀A,P,n,l.
   ]
 ] qed.
 
+lemma All_append: ∀A,P,l1,l2. All A P l1 → All A P l2 → All A P (l1@l2).
+#A #P #l1 elim l1 -l1 //
+#a #l1 #IHl1 #l2 * /3 width=1/
+qed.
+
+lemma All_inv_append: ∀A,P,l1,l2. All A P (l1@l2) → All A P l1 ∧ All A P l2.
+#A #P #l1 elim l1 -l1 /2 width=1/
+#a #l1 #IHl1 #l2 * #Ha #Hl12
+elim (IHl1 … Hl12) -IHl1 -Hl12 /3 width=1/
+qed-.
+
+(**************************** Allr ******************************)
+
 let rec Allr (A:Type[0]) (R:relation A) (l:list A) on l : Prop ≝
 match l with
 [ nil       ⇒ True
 | cons a1 l ⇒ match l with [ nil ⇒ True | cons a2 _ ⇒ R a1 a2 ∧ Allr A R l ]
 ].
 
+lemma Allr_fwd_append_sn: ∀A,R,l1,l2. Allr A R (l1@l2) → Allr A R l1.
+#A #R #l1 elim l1 -l1 // #a1 * // #a2 #l1 #IHl1 #l2 * /3 width=2/
+qed-.
+
+lemma Allr_fwd_cons: ∀A,R,a,l. Allr A R (a::l) → Allr A R l.
+#A #R #a * // #a0 #l * //
+qed-.
+
 (**************************** Exists *******************************)
 
 let rec Exists (A:Type[0]) (P:A → Prop) (l:list A) on l : Prop ≝