X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Flib%2Fbasics%2Flists%2Flistb.ma;h=a95d8a05adb91bcb3eeb7054f200d4759cfe632c;hb=85a42e4a2a4c62818b6a98eff545e58ceb8770a4;hp=c972326448fd65aee99a8024357cabfdec47b130;hpb=927bda3b4b7fe5f521ae73eb008a746e8606a0b4;p=helm.git

diff --git a/matita/matita/lib/basics/lists/listb.ma b/matita/matita/lib/basics/lists/listb.ma
index c97232644..a95d8a05a 100644
--- a/matita/matita/lib/basics/lists/listb.ma
+++ b/matita/matita/lib/basics/lists/listb.ma
@@ -16,6 +16,13 @@ include "basics/lists/list.ma".
 include "basics/sets.ma".
 include "basics/deqsets.ma".
 
+(********* isnilb *********)
+let rec isnilb A (l: list A) on l ≝
+match l with
+[ nil ⇒ true
+| cons hd tl ⇒ false
+].
+
 (********* search *********)
 
 let rec memb (S:DeqSet) (x:S) (l: list S) on l  ≝
@@ -24,8 +31,7 @@ let rec memb (S:DeqSet) (x:S) (l: list S) on l  ≝
   | cons a tl ⇒ (x == a) ∨ memb S x tl
   ].
 
-notation < "\memb x l" non associative with precedence 90 for @{'memb $x $l}.
-interpretation "boolean membership" 'memb a l = (memb ? a l).
+interpretation "boolean membership" 'mem a l = (memb ? a l).
 
 lemma memb_hd: ∀S,a,l. memb S a (a::l) = true.
 #S #a #l normalize >(proj2 … (eqb_true S …) (refl S a)) //
@@ -97,6 +103,34 @@ lemma memb_compose: ∀S1,S2,S3,op,a1,a2,l1,l2.
   ]
 qed.
 
+lemma memb_reverse: ∀S:DeqSet.∀a:S.∀l.
+  memb ? a l = true → memb ? a (reverse ? l) = true.
+#S #a #l elim l [normalize //]
+#b #tl #Hind #memba change with ([b]@tl) in match (b::tl);
+>reverse_append cases (orb_true_l … memba) #Hcase
+  [@memb_append_l2 >(\P Hcase) whd in match (reverse ??); @memb_hd
+  |@memb_append_l1 /2/
+  ]
+qed.
+
+lemma mem_to_memb: ∀S:DeqSet.∀a,l. mem S a l → memb S a l = true.
+#S #a #l elim l normalize
+  [@False_ind
+  |#hd #tl #Hind *
+    [#eqa >(\b eqa) %
+    |#Hmem cases (a==hd) // normalize /2/
+    ]
+  ]
+qed.
+
+lemma memb_to_mem: ∀S:DeqSet.∀l,a. memb S a l =true → mem S a l.
+#S #l #a elim l 
+  [normalize #H destruct
+  |#b #tl #Hind #mema cases (orb_true_l … mema) 
+    [#eqab >(\P eqab) %1 % |#memtl %2 @Hind @memtl]
+  ]
+qed.
+
 (**************** unicity test *****************)
 
 let rec uniqueb (S:DeqSet) l on l : bool ≝
@@ -115,9 +149,21 @@ let rec unique_append (S:DeqSet) (l1,l2: list S) on l1 ≝
      if memb S a r then r else a::r
   ].
 
-axiom unique_append_elim: ∀S:DeqSet.∀P: S → Prop.∀l1,l2. 
+lemma memb_unique_append: ∀S,a,l1,l2. 
+memb S a (unique_append S l1 l2) = true →
+  memb S a l1= true ∨ memb S a l2 = true.
+#S #a #l1 elim l1 normalize [#l2 #H %2 //] 
+#b #tl #Hind #l2 cases (true_or_false … (a==b)) #Hab >Hab normalize /2/
+cases (memb S b (unique_append S tl l2)) normalize 
+  [@Hind | >Hab normalize @Hind]   
+qed. 
+
+lemma unique_append_elim: ∀S:DeqSet.∀P: S → Prop.∀l1,l2. 
 (∀x. memb S x l1 = true → P x) → (∀x. memb S x l2 = true → P x) →
 ∀x. memb S x (unique_append S l1 l2) = true → P x. 
+#S #P #l1 #l2 #Hl1 #Hl2 #x #membx cases (memb_unique_append … membx)
+/2/ 
+qed.
 
 lemma unique_append_unique: ∀S,l1,l2. uniqueb S l2 = true →
   uniqueb S (unique_append S l1 l2) = true.
@@ -126,6 +172,30 @@ cases (true_or_false … (memb S a (unique_append S tl l2)))
 #H >H normalize [@Hind //] >H normalize @Hind //
 qed.
 
+lemma memb_map_inj: ∀A,B:DeqSet.∀f:A→B.∀l,a. injective A B f → 
+  memb ? (f a) (map ?? f l) = true → memb ? a l = true.
+#A #B #f #l #a #injf elim l
+  [normalize //
+  |#a1 #tl #Hind #Ha cases (orb_true_l … Ha)
+    [#eqf @orb_true_r1 @(\b ?)  >(injf … (\P eqf)) //
+    |#membtl @orb_true_r2 /2/
+    ]
+  ]
+qed.
+
+lemma unique_map_inj: ∀A,B:DeqSet.∀f:A→B.∀l. injective A B f → 
+  uniqueb A l = true → uniqueb B (map ?? f l) = true .
+#A #B #f #l #injf elim l 
+  [normalize //
+  |#a #tl #Hind #Htl @true_to_andb_true
+    [@sym_eq @noteq_to_eqnot @sym_not_eq 
+     @(not_to_not ?? (memb_map_inj … injf …) )
+     <(andb_true_l ?? Htl) /2/
+    |@Hind @(andb_true_r ?? Htl)
+    ]
+  ]
+qed.
+
 (******************* sublist *******************)
 definition sublist ≝ 
   λS,l1,l2.∀a. memb S a l1 = true → memb S a l2 = true.
@@ -183,6 +253,27 @@ qed.
 
 (********************* filtering *****************)
 
+lemma memb_filter_memb: ∀S,f,a,l. 
+  memb S a (filter S f l) = true → memb S a l = true.
+#S #f #a #l elim l [normalize //]
+#b #tl #Hind normalize (cases (f b)) normalize 
+cases (a==b) normalize // @Hind
+qed.
+  
+lemma uniqueb_filter : ∀S,l,f.
+ uniqueb S l = true → uniqueb S (filter S f l) = true.
+#S #l #f elim l //
+#a #tl #Hind #Hunique cases (andb_true … Hunique)
+#memba #uniquetl cases (true_or_false … (f a)) #Hfa
+  [>filter_true // @true_to_andb_true
+    [@sym_eq @noteq_to_eqnot @(not_to_not … (eqnot_to_noteq … (sym_eq … memba)))
+     #H @sym_eq @(memb_filter_memb … f) <H // 
+    |/2/
+    ]
+  |>filter_false /2/
+  ]
+qed.
+  
 lemma filter_true: ∀S,f,a,l. 
   memb S a (filter S f l) = true → f a = true.
 #S #f #a #l elim l [normalize #H @False_ind /2/]
@@ -192,13 +283,6 @@ cases (true_or_false (a==b)) #eqab
   [#_ >(\P eqab) // | >eqab normalize @Hind]
 qed. 
   
-lemma memb_filter_memb: ∀S,f,a,l. 
-  memb S a (filter S f l) = true → memb S a l = true.
-#S #f #a #l elim l [normalize //]
-#b #tl #Hind normalize (cases (f b)) normalize 
-cases (a==b) normalize // @Hind
-qed.
-  
 lemma memb_filter: ∀S,f,l,x. memb S x (filter ? f l) = true → 
 memb S x l = true ∧ (f x = true).
 /3/ qed.