-include "tutorial/chapter3.ma".
+(*
+\ 5h1 class="section"\ 6Naif Set Theory\ 5/h1\ 6
+*)
+include "basics/types.ma".
+include "basics/bool.ma".
+(*
+In this Chapter we shall develop a naif theory of sets represented as
+characteristic predicates over some universe \ 5code\ 6A\ 5/code\ 6, that is as objects of type
+A→Prop.
+For instance the empty set is defined by the always false function: *)
+
+definition empty_set ≝ λA:Type[0].λa:A.\ 5a href="cic:/matita/basics/logic/False.ind(1,0,0)"\ 6False\ 5/a\ 6.
+notation "\emptyv" non associative with precedence 90 for @{'empty_set}.
+interpretation "empty set" 'empty_set = (empty_set ?).
+
+(* Similarly, a singleton set contaning containing an element a, is defined
+by by the characteristic function asserting equality with a *)
+
+definition singleton ≝ λA.λx,a:A.x\ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6\ 5span class="error" title="Parse error: [term] expected after [sym=] (in [term])"\ 6\ 5/span\ 6a.
+(* notation "{x}" non associative with precedence 90 for @{'sing_lang $x}. *)
+interpretation "singleton" 'singl x = (singleton ? x).
+
+(* The membership relation between an element of type A and a set S:A →Prop is
+simply the predicate resulting from the application of S to a.
+The operations of union, intersection, complement and substraction
+are easily defined in terms of the propositional connectives of dijunction,
+conjunction and negation *)
+
+definition union : ∀A:Type[0].∀P,Q.A → Prop ≝ λA,P,Q,a.P a \ 5a title="logical or" href="cic:/fakeuri.def(1)"\ 6∨\ 5/a\ 6 Q a.
+interpretation "union" 'union a b = (union ? a b).
+
+definition intersection : ∀A:Type[0].∀P,Q.A→Prop ≝ λA,P,Q,a.P a \ 5a title="logical and" href="cic:/fakeuri.def(1)"\ 6∧\ 5/a\ 6\ 5span class="error" title="Parse error: [term] expected after [sym∧] (in [term])"\ 6\ 5/span\ 6 Q a.
+interpretation "intersection" 'intersects a b = (intersection ? a b).
+
+definition complement ≝ λU:Type[0].λA:U → Prop.λw.\ 5a title="logical not" href="cic:/fakeuri.def(1)"\ 6¬\ 5/a\ 6 A w.
+interpretation "complement" 'not a = (complement ? a).
+
+definition substraction := λU:Type[0].λA,B:U → Prop.λw.A w \ 5a title="logical and" href="cic:/fakeuri.def(1)"\ 6∧\ 5/a\ 6 \ 5a title="logical not" href="cic:/fakeuri.def(1)"\ 6¬\ 5/a\ 6 B w.
+interpretation "substraction" 'minus a b = (substraction ? a b).
-(* As a simple application of lists, let us now consider strings of characters
-over a given alphabet Alpha. We shall assume to have a decidable equality between
-characters, that is a (computable) function eqb associating a boolean value true
-or false to each pair of characters; eqb is correct, in the sense that (eqb x y)
-if and only if (x = y). The type Alpha of alphabets is hence defined by the
-following record *)
+(* Finally, we use implication to define the inclusion relation between
+sets *)
-interpretation "iff" 'iff a b = (iff a b).
+definition subset: ∀A:Type[0].∀P,Q:A→Prop.Prop ≝ λA,P,Q.∀a:A.(P a → Q a).
+interpretation "subset" 'subseteq a b = (subset ? a b).
-record Alpha : Type[1] ≝ { carr :> Type[0];
+(* Two sets are equals if and only if they have the same elements, that is,
+if the two characteristic functions are extensionally equivalent: *)
+
+definition eqP ≝ λA:Type[0].λP,Q:A → Prop.∀a:A.P a \ 5a title="iff" href="cic:/fakeuri.def(1)"\ 6↔\ 5/a\ 6\ 5span class="error" title="Parse error: [term] expected after [sym↔] (in [term])"\ 6\ 5/span\ 6 Q a.
+notation "A =1 B" non associative with precedence 45 for @{'eqP $A $B}.
+interpretation "extensional equality" 'eqP a b = (eqP ? a b).
+
+(* This notion of equality is different from the intensional equality of
+functions; the fact it defines an equivalence relation must be explicitly
+proved: *)
+
+lemma eqP_sym: ∀U.∀A,B:U →Prop.
+ A \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 B → B \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 A.
+#U #A #B #eqAB #a @\ 5a href="cic:/matita/basics/logic/iff_sym.def(2)"\ 6iff_sym\ 5/a\ 6 @eqAB qed.
+
+lemma eqP_trans: ∀U.∀A,B,C:U →Prop.
+ A \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 B → B \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 C → A \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 C.
+#U #A #B #C #eqAB #eqBC #a @\ 5a href="cic:/matita/basics/logic/iff_trans.def(2)"\ 6iff_trans\ 5/a\ 6 // qed.
+
+(* For the same reason, we must also prove that all the operations behave well
+with respect to eqP: *)
+
+lemma eqP_union_r: ∀U.∀A,B,C:U →Prop.
+ A \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6\ 5span class="error" title="Parse error: NUMBER '1' or [term] expected after [sym=] (in [term])"\ 6\ 5/span\ 61 C → A \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 B \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 C \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 B.
+#U #A #B #C #eqAB #a @\ 5a href="cic:/matita/basics/logic/iff_or_r.def(2)"\ 6iff_or_r\ 5/a\ 6 @eqAB qed.
+
+lemma eqP_union_l: ∀U.∀A,B,C:U →Prop.
+ B \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 C → A \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 B \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 A \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 C.
+#U #A #B #C #eqBC #a @\ 5a href="cic:/matita/basics/logic/iff_or_l.def(2)"\ 6iff_or_l\ 5/a\ 6 @eqBC qed.
+
+lemma eqP_intersect_r: ∀U.∀A,B,C:U →Prop.
+ A \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 C → A \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6 B \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 C \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6 B.
+#U #A #B #C #eqAB #a @\ 5a href="cic:/matita/basics/logic/iff_and_r.def(2)"\ 6iff_and_r\ 5/a\ 6 @eqAB qed.
+
+lemma eqP_intersect_l: ∀U.∀A,B,C:U →Prop.
+ B \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 C → A \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6\ 5span class="error" title="Parse error: [term] expected after [sym∩] (in [term])"\ 6\ 5/span\ 6 B \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 A \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6 C.
+#U #A #B #C #eqBC #a @\ 5a href="cic:/matita/basics/logic/iff_and_l.def(2)"\ 6iff_and_l\ 5/a\ 6 @eqBC qed.
+
+lemma eqP_substract_r: ∀U.∀A,B,C:U →Prop.
+ A \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 C → A \ 5a title="substraction" href="cic:/fakeuri.def(1)"\ 6-\ 5/a\ 6 B \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 C \ 5a title="substraction" href="cic:/fakeuri.def(1)"\ 6-\ 5/a\ 6 B.
+#U #A #B #C #eqAB #a @\ 5a href="cic:/matita/basics/logic/iff_and_r.def(2)"\ 6iff_and_r\ 5/a\ 6 @eqAB qed.
+
+lemma eqP_substract_l: ∀U.∀A,B,C:U →Prop.
+ B \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 C → A \ 5a title="substraction" href="cic:/fakeuri.def(1)"\ 6-\ 5/a\ 6 B \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 A \ 5a title="substraction" href="cic:/fakeuri.def(1)"\ 6-\ 5/a\ 6 C.
+#U #A #B #C #eqBC #a @\ 5a href="cic:/matita/basics/logic/iff_and_l.def(2)"\ 6iff_and_l\ 5/a\ 6 /\ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/iff_not.def(4)"\ 6iff_not\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/ qed.
+
+(* We can now prove several properties of the previous set-theoretic operations.
+In particular, union is commutative and associative, and the empty set is an
+identity element: *)
+
+lemma union_empty_r: ∀U.∀A:U→Prop.
+ A \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 \ 5a title="empty set" href="cic:/fakeuri.def(1)"\ 6∅\ 5/a\ 6 \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 A.
+#U #A #w % [* // normalize #abs @\ 5a href="cic:/matita/basics/logic/False_ind.fix(0,1,1)"\ 6False_ind\ 5/a\ 6 /\ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5/span\ 6\ 5/span\ 6/ | /\ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/Or.con(0,1,2)"\ 6or_introl\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/]
+qed.
+
+lemma union_comm : ∀U.∀A,B:U →Prop.
+ A \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 B \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 B \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 A.
+#U #A #B #a % * /\ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/Or.con(0,1,2)"\ 6or_introl\ 5/a\ 6, \ 5a href="cic:/matita/basics/logic/Or.con(0,2,2)"\ 6or_intror\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/ qed.
+
+lemma union_assoc: ∀U.∀A,B,C:U → Prop.
+ A \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 B \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 C \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 A \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 (B \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 C).
+#S #A #B #C #w % [* [* /\ 5span class="autotactic"\ 63\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/Or.con(0,1,2)"\ 6or_introl\ 5/a\ 6, \ 5a href="cic:/matita/basics/logic/Or.con(0,2,2)"\ 6or_intror\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/ | /\ 5span class="autotactic"\ 63\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/Or.con(0,1,2)"\ 6or_introl\ 5/a\ 6, \ 5a href="cic:/matita/basics/logic/Or.con(0,2,2)"\ 6or_intror\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/ ] | * [/\ 5span class="autotactic"\ 63\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/Or.con(0,1,2)"\ 6or_introl\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/ | * /\ 5span class="autotactic"\ 63\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/Or.con(0,1,2)"\ 6or_introl\ 5/a\ 6, \ 5a href="cic:/matita/basics/logic/Or.con(0,2,2)"\ 6or_intror\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/]
+qed.
+
+(* In the same way we prove commutativity and associativity for set
+interesection *)
+
+lemma cap_comm : ∀U.∀A,B:U →Prop.
+ A \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6 B \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 B \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6 A.
+#U #A #B #a % * /\ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/And.con(0,1,2)"\ 6conj\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/ qed.
+
+lemma cap_assoc: ∀U.∀A,B,C:U→Prop.
+ A \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6 (B \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6 C) \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 (A \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6 B) \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6 C.
+#U #A #B #C #w % [ * #Aw * /\ 5span class="autotactic"\ 63\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/And.con(0,1,2)"\ 6conj\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/ \ 5span class="autotactic"\ 6\ 5span class="autotrace"\ 6\ 5/span\ 6\ 5/span\ 6| * * /\ 5span class="autotactic"\ 63\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/And.con(0,1,2)"\ 6conj\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/ ]
+qed.
+
+(* We can also easily prove idempotency for union and intersection *)
+
+lemma union_idemp: ∀U.∀A:U →Prop.
+ A \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 A \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 A.
+#U #A #a % [* // | /\ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/Or.con(0,2,2)"\ 6or_intror\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/] qed.
+
+lemma cap_idemp: ∀U.∀A:U →Prop.
+ A \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6 A \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 A.
+#U #A #a % [* // | /\ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/And.con(0,1,2)"\ 6conj\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/] qed.
+
+(* We conclude our examples with a couple of distributivity theorems, and a
+characterization of substraction in terms of interesection and complementation. *)
+
+lemma distribute_intersect : ∀U.∀A,B,C:U→Prop.
+ (A \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 B) \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6 C \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 (A \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6 C) \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 (B \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6 C).
+#U #A #B #C #w % [* * /\ 5span class="autotactic"\ 63\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/Or.con(0,1,2)"\ 6or_introl\ 5/a\ 6, \ 5a href="cic:/matita/basics/logic/Or.con(0,2,2)"\ 6or_intror\ 5/a\ 6, \ 5a href="cic:/matita/basics/logic/And.con(0,1,2)"\ 6conj\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/ | * * /\ 5span class="autotactic"\ 63\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/Or.con(0,1,2)"\ 6or_introl\ 5/a\ 6, \ 5a href="cic:/matita/basics/logic/Or.con(0,2,2)"\ 6or_intror\ 5/a\ 6, \ 5a href="cic:/matita/basics/logic/And.con(0,1,2)"\ 6conj\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/]
+qed.
+
+lemma distribute_substract : ∀U.∀A,B,C:U→Prop.
+ (A \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 B) \ 5a title="substraction" href="cic:/fakeuri.def(1)"\ 6-\ 5/a\ 6 C \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 (A \ 5a title="substraction" href="cic:/fakeuri.def(1)"\ 6-\ 5/a\ 6 C) \ 5a title="union" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 (B \ 5a title="substraction" href="cic:/fakeuri.def(1)"\ 6-\ 5/a\ 6 C).
+#U #A #B #C #w % [* * /\ 5span class="autotactic"\ 63\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/Or.con(0,1,2)"\ 6or_introl\ 5/a\ 6, \ 5a href="cic:/matita/basics/logic/Or.con(0,2,2)"\ 6or_intror\ 5/a\ 6, \ 5a href="cic:/matita/basics/logic/And.con(0,1,2)"\ 6conj\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/ | * * /\ 5span class="autotactic"\ 63\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/Or.con(0,1,2)"\ 6or_introl\ 5/a\ 6, \ 5a href="cic:/matita/basics/logic/Or.con(0,2,2)"\ 6or_intror\ 5/a\ 6, \ 5a href="cic:/matita/basics/logic/And.con(0,1,2)"\ 6conj\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/]
+qed.
+
+lemma substract_def:∀U.∀A,B:U→Prop. A\ 5a title="substraction" href="cic:/fakeuri.def(1)"\ 6-\ 5/a\ 6B \ 5a title="extensional equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 61 A \ 5a title="intersection" href="cic:/fakeuri.def(1)"\ 6∩\ 5/a\ 6 \ 5a title="complement" href="cic:/fakeuri.def(1)"\ 6¬\ 5/a\ 6B.
+#U #A #B #w normalize /\ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/And.con(0,1,2)"\ 6conj\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/
+qed.
+
+(*
+\ 5h2 class="section"\ 6Bool vs. Prop\ 5/h2\ 6
+In several situation it is important to assume to have a decidable equality
+between elements of a set U, namely a boolean function eqb: U→U→bool such that
+for any pair of elements a and b in U, (eqb x y) is true if and only if x=y.
+A set equipped with such an equality is called a DeqSet: *)
+
+record DeqSet : Type[1] ≝ { carr :> Type[0];
eqb: carr → carr → \ 5a href="cic:/matita/basics/bool/bool.ind(1,0,0)"\ 6bool\ 5/a\ 6;
eqb_true: ∀x,y. (eqb x y \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 \ 5a href="cic:/matita/basics/bool/bool.con(0,1,0)"\ 6true\ 5/a\ 6) \ 5a title="iff" href="cic:/fakeuri.def(1)"\ 6↔\ 5/a\ 6 (x \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 y)
}.
-
+
+(* We use the notation == to denote the decidable equality, to distinguish it
+from the propositional equality. In particular, a term of the form a==b is a
+boolean, while a=b is a proposition. *)
+
notation "a == b" non associative with precedence 45 for @{ 'eqb $a $b }.
interpretation "eqb" 'eqb a b = (eqb ? a b).
-definition word ≝ λS: \ 5a href="cic:/matita/tutorial/chapter4/Alpha.ind(1,0,0)"\ 6Alpha\ 5/a\ 6.\ 5a href="cic:/matita/tutorial/chapter3/list.ind(1,0,1)"\ 6list\ 5/a\ 6 S.
+(*
+\ 5h2 class="section"\ 6Small Scale Reflection\ 5/h2\ 6
+It is convenient to have a simple way to reflect a proof of the fact
+that (eqb a b) is true into a proof of the proposition (a = b); to this aim,
+we introduce two operators "\P" and "\b". *)
-inductive re (S: \ 5a href="cic:/matita/tutorial/chapter4/Alpha.ind(1,0,0)"\ 6Alpha\ 5/a\ 6) : Type[0] ≝
- zero: re S
- | epsilon: re S
- | char: S → re S
- | concat: re S → re S → re S
- | or: re S → re S → re S
- | star: re S → re S.
-
-(* notation < "a \sup ⋇" non associative with precedence 90 for @{ 'pk $a}. *)
-notation "a ^ *" non associative with precedence 90 for @{ 'kstar $a}.
-interpretation "star" 'kstar a = (star ? a).
-interpretation "or" 'plus a b = (or ? a b).
-
-notation "a · b" non associative with precedence 60 for @{ 'concat $a $b}.
-interpretation "cat" 'concat a b = (concat ? a b).
-
-(* to get rid of \middot
-coercion c : ∀S:Alpha.∀p:re S. re S → re S ≝ c on _p : re ? to ∀_:?.?. *)
-
-(* notation < "a" non associative with precedence 90 for @{ 'ps $a}. *)
-notation "` term 90 a" non associative with precedence 90 for @{ 'atom $a}.
-interpretation "atom" 'atom a = (char ? a).
-
-notation "ϵ" non associative with precedence 90 for @{ 'epsilon }.
-interpretation "epsilon" 'epsilon = (epsilon ?).
-
-notation "∅" (* slash emptyv *) non associative with precedence 90 for @{ 'empty }.
-interpretation "empty" 'empty = (zero ?).
-
-let rec flatten (S : \ 5a href="cic:/matita/tutorial/chapter4/Alpha.ind(1,0,0)"\ 6Alpha\ 5/a\ 6) (l : \ 5a href="cic:/matita/tutorial/chapter3/list.ind(1,0,1)"\ 6list\ 5/a\ 6 (\ 5a href="cic:/matita/tutorial/chapter4/word.def(3)"\ 6word\ 5/a\ 6 S)) on l : \ 5a href="cic:/matita/tutorial/chapter4/word.def(3)"\ 6word\ 5/a\ 6 S ≝
-match l with [ nil ⇒ \ 5a title="nil" href="cic:/fakeuri.def(1)"\ 6[\ 5/a\ 6 ] | cons w tl ⇒ w \ 5a title="append" href="cic:/fakeuri.def(1)"\ 6@\ 5/a\ 6 flatten ? tl ].
-
-let rec conjunct (S : \ 5a href="cic:/matita/tutorial/chapter4/Alpha.ind(1,0,0)"\ 6Alpha\ 5/a\ 6) (l : \ 5a href="cic:/matita/tutorial/chapter3/list.ind(1,0,1)"\ 6list\ 5/a\ 6 (\ 5a href="cic:/matita/tutorial/chapter4/word.def(3)"\ 6word\ 5/a\ 6 S)) (L :\ 5a href="cic:/matita/tutorial/chapter4/word.def(3)"\ 6word\ 5/a\ 6 S → Prop) on l: Prop ≝
-match l with [ nil ⇒ \ 5a href="cic:/matita/basics/logic/True.ind(1,0,0)"\ 6True\ 5/a\ 6 | cons w tl ⇒ L w \ 5a title="logical and" href="cic:/fakeuri.def(1)"\ 6∧\ 5/a\ 6 conjunct ? tl L ].
-
-definition empty_lang ≝ λS.λw:\ 5a href="cic:/matita/tutorial/chapter4/word.def(3)"\ 6word\ 5/a\ 6 S.\ 5a href="cic:/matita/basics/logic/False.ind(1,0,0)"\ 6False\ 5/a\ 6.
-(* notation "{}" non associative with precedence 90 for @{'empty_lang}. *)
-interpretation "empty lang" 'empty = (empty_lang ?).
-
-definition sing_lang ≝ λS.λx,w:\ 5a href="cic:/matita/tutorial/chapter4/word.def(3)"\ 6word\ 5/a\ 6 S.x \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 w.
-notation "{: x }" non associative with precedence 90 for @{'sing_lang $x}.
-interpretation "sing lang" 'sing_lang x = (sing_lang ? x).
-
-definition union : ∀S,L1,L2,w.Prop ≝ λS,L1,L2.λw: \ 5a href="cic:/matita/tutorial/chapter4/word.def(3)"\ 6word\ 5/a\ 6 S.L1 w \ 5a title="logical or" href="cic:/fakeuri.def(1)"\ 6∨\ 5/a\ 6 L2 w.
-interpretation "union lang" 'union a b = (union ? a b).
-
-definition cat : ∀S,l1,l2,w.Prop ≝
- λS.λl1,l2.λw:\ 5a href="cic:/matita/tutorial/chapter4/word.def(3)"\ 6word\ 5/a\ 6 S.\ 5a title="exists" href="cic:/fakeuri.def(1)"\ 6∃\ 5/a\ 6w1,w2.w1 \ 5a title="append" href="cic:/fakeuri.def(1)"\ 6@\ 5/a\ 6 w2 \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 w \ 5a title="logical and" href="cic:/fakeuri.def(1)"\ 6∧\ 5/a\ 6 l1 w1 \ 5a title="logical and" href="cic:/fakeuri.def(1)"\ 6∧\ 5/a\ 6 l2 w2.
-interpretation "cat lang" 'concat a b = (cat ? a b).
-
-definition star_lang ≝ λS.λl.λw:\ 5a href="cic:/matita/tutorial/chapter4/word.def(3)"\ 6word\ 5/a\ 6 S.\ 5a title="exists" href="cic:/fakeuri.def(1)"\ 6∃\ 5/a\ 6lw. \ 5a href="cic:/matita/tutorial/chapter4/flatten.fix(0,1,4)"\ 6flatten\ 5/a\ 6 ? lw \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 w \ 5a title="logical and" href="cic:/fakeuri.def(1)"\ 6∧\ 5/a\ 6 \ 5a href="cic:/matita/tutorial/chapter4/conjunct.fix(0,1,4)"\ 6conjunct\ 5/a\ 6 ? lw l.
-interpretation "star lang" 'kstar l = (star_lang ? l).
-
-(* notation "| term 70 E| " non associative with precedence 75 for @{in_l ? $E}. *)
-
-let rec in_l (S : \ 5a href="cic:/matita/tutorial/chapter4/Alpha.ind(1,0,0)"\ 6Alpha\ 5/a\ 6) (r : \ 5a href="cic:/matita/tutorial/chapter4/re.ind(1,0,1)"\ 6re\ 5/a\ 6 S) on r : \ 5a href="cic:/matita/tutorial/chapter4/word.def(3)"\ 6word\ 5/a\ 6 S → Prop ≝
-match r with
- [ zero ⇒ \ 5a title="empty lang" href="cic:/fakeuri.def(1)"\ 6∅\ 5/a\ 6
- | epsilon ⇒ \ 5a title="sing lang" href="cic:/fakeuri.def(1)"\ 6{\ 5/a\ 6: \ 5a title="nil" href="cic:/fakeuri.def(1)"\ 6[\ 5/a\ 6] }
- | char x ⇒ \ 5a title="sing lang" href="cic:/fakeuri.def(1)"\ 6{\ 5/a\ 6: x\ 5a title="cons" href="cic:/fakeuri.def(1)"\ 6:\ 5/a\ 6:\ 5a title="nil" href="cic:/fakeuri.def(1)"\ 6[\ 5/a\ 6] }
- | concat r1 r2 ⇒ in_l ? r1 \ 5a title="cat lang" href="cic:/fakeuri.def(1)"\ 6·\ 5/a\ 6 in_l ? r2
- | or r1 r2 ⇒ in_l ? r1 \ 5a title="union lang" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 in_l ? r2
- | star r1 ⇒ (in_l ? r1)\ 5a title="star lang" href="cic:/fakeuri.def(1)"\ 6^\ 5/a\ 6*
- ].
-
-notation "\sem{E}" non associative with precedence 75 for @{'sem $E}.
-interpretation "in_l" 'sem E = (in_l ? E).
-interpretation "in_l mem" 'mem w l = (in_l ? l w).
-
-notation "a ∨ b" left associative with precedence 30 for @{'orb $a $b}.
-interpretation "orb" 'orb a b = (orb a b).
-
-(* ndefinition if_then_else ≝ λT:Type[0].λe,t,f.match e return λ_.T with [ true ⇒ t | false ⇒ f].
-notation > "'if' term 19 e 'then' term 19 t 'else' term 19 f" non associative with precedence 19 for @{ 'if_then_else $e $t $f }.
-notation < "'if' \nbsp term 19 e \nbsp 'then' \nbsp term 19 t \nbsp 'else' \nbsp term 90 f \nbsp" non associative with precedence 19 for @{ 'if_then_else $e $t $f }.
-interpretation "if_then_else" 'if_then_else e t f = (if_then_else ? e t f). *)
-
-inductive pitem (S: \ 5a href="cic:/matita/tutorial/chapter4/Alpha.ind(1,0,0)"\ 6Alpha\ 5/a\ 6) : Type[0] ≝
- | pzero: pitem S
- | pepsilon: pitem S
- | pchar: S → pitem S
- | ppoint: S → pitem S
- | pconcat: pitem S → pitem S → pitem S
- | por: pitem S → pitem S → pitem S
- | pstar: pitem S → pitem S.
+notation "\P H" non associative with precedence 90
+ for @{(proj1 … (eqb_true ???) $H)}.
+
+notation "\b H" non associative with precedence 90
+ for @{(proj2 … (eqb_true ???) $H)}.
+
+(* If H:eqb a b = true, then \P H: a = b, and conversely if h:a = b, then
+\b h: eqb a b = true. Let us see an example of their use: the following
+statement asserts that we can reflect a proof that eqb a b is false into
+a proof of the proposition a ≠ b. *)
+
+lemma eqb_false: ∀S:\ 5a href="cic:/matita/tutorial/chapter4/DeqSet.ind(1,0,0)"\ 6DeqSet\ 5/a\ 6.∀a,b:S.
+ (\ 5a href="cic:/matita/tutorial/chapter4/eqb.fix(0,0,3)"\ 6eqb\ 5/a\ 6 ? a b) \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 \ 5a href="cic:/matita/basics/bool/bool.con(0,2,0)"\ 6false\ 5/a\ 6 \ 5a title="iff" href="cic:/fakeuri.def(1)"\ 6↔\ 5/a\ 6 a \ 5a title="leibnitz's non-equality" href="cic:/fakeuri.def(1)"\ 6≠\ 5/a\ 6 b.
+
+(* We start the proof introducing the hypothesis, and then split the "if" and
+"only if" cases *)
-definition pre ≝ λS.\ 5a href="cic:/matita/tutorial/chapter4/pitem.ind(1,0,1)"\ 6pitem\ 5/a\ 6 S \ 5a title="Product" href="cic:/fakeuri.def(1)"\ 6×\ 5/a\ 6 \ 5a href="cic:/matita/basics/bool/bool.ind(1,0,0)" title="null"\ 6bool\ 5/a\ 6.
-
-interpretation "pstar" 'kstar a = (pstar ? a).
-interpretation "por" 'plus a b = (por ? a b).
-interpretation "pcat" 'concat a b = (pconcat ? a b).
-
-notation "• a" non associative with precedence 90 for @{ 'ppoint $a}.
-(* notation > "`. term 90 a" non associative with precedence 90 for @{ 'pp $a}. *)
-
-interpretation "ppatom" 'ppoint a = (ppoint ? a).
-(* to get rid of \middot
-ncoercion pc : ∀S.∀p:pitem S. pitem S → pitem S ≝ pc on _p : pitem ? to ∀_:?.?. *)
-interpretation "patom" 'pchar a = (pchar ? a).
-interpretation "pepsilon" 'epsilon = (pepsilon ?).
-interpretation "pempty" 'empty = (pzero ?).
-
-notation "| e |" non associative with precedence 65 for @{forget ? $e}.
-
-let rec forget (S: \ 5a href="cic:/matita/tutorial/chapter4/Alpha.ind(1,0,0)"\ 6Alpha\ 5/a\ 6) (l : \ 5a href="cic:/matita/tutorial/chapter4/pitem.ind(1,0,1)"\ 6pitem\ 5/a\ 6 S) on l: \ 5a href="cic:/matita/tutorial/chapter4/re.ind(1,0,1)"\ 6re\ 5/a\ 6 S ≝
- match l with
- [ pzero ⇒ \ 5a title="empty" href="cic:/fakeuri.def(1)"\ 6∅\ 5/a\ 6
- | pepsilon ⇒ \ 5a title="epsilon" href="cic:/fakeuri.def(1)"\ 6ϵ\ 5/a\ 6
- | pchar x ⇒ \ 5a href="cic:/matita/tutorial/chapter4/re.con(0,3,1)"\ 6char\ 5/a\ 6 ? x
- | ppoint x ⇒ \ 5a href="cic:/matita/tutorial/chapter4/re.con(0,3,1)"\ 6char\ 5/a\ 6 ? x
- | pconcat e1 e2 ⇒ |e1| \ 5a title="cat" href="cic:/fakeuri.def(1)"\ 6·\ 5/a\ 6 |e2|
- | por e1 e2 ⇒ |e1| \ 5a title="or" href="cic:/fakeuri.def(1)"\ 6+\ 5/a\ 6 |e2|
- | pstar e ⇒ |e|\ 5a title="star" href="cic:/fakeuri.def(1)"\ 6^\ 5/a\ 6*
- ].
-
-notation "| e |" non associative with precedence 65 for @{'fmap $e}.
-interpretation "forget" 'fmap a = (forget ? a).
-
-let rec in_pl (S : \ 5a href="cic:/matita/tutorial/chapter4/Alpha.ind(1,0,0)"\ 6Alpha\ 5/a\ 6) (r : \ 5a href="cic:/matita/tutorial/chapter4/pitem.ind(1,0,1)"\ 6pitem\ 5/a\ 6 S) on r : \ 5a href="cic:/matita/tutorial/chapter4/word.def(3)"\ 6word\ 5/a\ 6 S → Prop ≝
-match r with
- [ pzero ⇒ \ 5a title="empty lang" href="cic:/fakeuri.def(1)"\ 6∅\ 5/a\ 6
- | pepsilon ⇒ \ 5a title="empty lang" href="cic:/fakeuri.def(1)"\ 6∅\ 5/a\ 6
- | pchar _ ⇒ \ 5a title="empty lang" href="cic:/fakeuri.def(1)"\ 6∅\ 5/a\ 6
- | ppoint x ⇒ \ 5a title="sing lang" href="cic:/fakeuri.def(1)"\ 6{\ 5/a\ 6: x\ 5a title="cons" href="cic:/fakeuri.def(1)"\ 6:\ 5/a\ 6:\ 5a title="nil" href="cic:/fakeuri.def(1)"\ 6[\ 5/a\ 6] }
- | pconcat pe1 pe2 ⇒ in_pl ? pe1 \ 5a title="cat lang" href="cic:/fakeuri.def(1)"\ 6·\ 5/a\ 6 \ 5a title="in_l" href="cic:/fakeuri.def(1)"\ 6\sem\ 5/a\ 6{|pe2|} \ 5a title="union lang" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 in_pl ? pe2
- | por pe1 pe2 ⇒ in_pl ? pe1 \ 5a title="union lang" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 in_pl ? pe2
- | pstar pe ⇒ in_pl ? pe \ 5a title="cat lang" href="cic:/fakeuri.def(1)"\ 6·\ 5/a\ 6 \ 5a title="in_l" href="cic:/fakeuri.def(1)"\ 6\sem\ 5/a\ 6{|pe|}\ 5a title="star lang" href="cic:/fakeuri.def(1)"\ 6^\ 5/a\ 6*
- ].
-
-interpretation "in_pl" 'sem E = (in_pl ? E).
-interpretation "in_pl mem" 'mem w l = (in_pl ? l w).
-
-definition eps: ∀S:\ 5a href="cic:/matita/tutorial/chapter4/Alpha.ind(1,0,0)"\ 6Alpha\ 5/a\ 6.\ 5a href="cic:/matita/basics/bool/bool.ind(1,0,0)"\ 6bool\ 5/a\ 6 → \ 5a href="cic:/matita/tutorial/chapter4/word.def(3)"\ 6word\ 5/a\ 6 S → Prop
- ≝ λS,b. \ 5a href="cic:/matita/basics/bool/if_then_else.def(1)"\ 6if_then_else\ 5/a\ 6 ? b \ 5a title="sing lang" href="cic:/fakeuri.def(1)"\ 6{\ 5/a\ 6: \ 5a title="nil" href="cic:/fakeuri.def(1)"\ 6[\ 5/a\ 6] } \ 5a title="empty lang" href="cic:/fakeuri.def(1)"\ 6∅\ 5/a\ 6.
-
-notation "ϵ _ b" non associative with precedence 90 for @{'app_epsilon $b}.
-interpretation "epsilon lang" 'app_epsilon b = (eps ? b).
-
-definition in_prl ≝ λS : \ 5a href="cic:/matita/tutorial/chapter4/Alpha.ind(1,0,0)"\ 6Alpha\ 5/a\ 6.λp:\ 5a href="cic:/matita/tutorial/chapter4/pre.def(1)"\ 6pre\ 5/a\ 6 S. \ 5a title="in_pl" href="cic:/fakeuri.def(1)"\ 6\sem\ 5/a\ 6{\ 5a title="pair pi1" href="cic:/fakeuri.def(1)"\ 6\fst\ 5/a\ 6 p} \ 5a title="union lang" href="cic:/fakeuri.def(1)"\ 6∪\ 5/a\ 6 \ 5a title="epsilon lang" href="cic:/fakeuri.def(1)"\ 6ϵ\ 5/a\ 6_(\ 5a title="pair pi2" href="cic:/fakeuri.def(1)"\ 6\snd\ 5/a\ 6 p).
+#S #a #b % #H
+
+(* The latter is easily reduced to prove the goal true=false under the assumption
+H1: a = b *)
+ [@(\ 5a href="cic:/matita/basics/logic/not_to_not.def(3)"\ 6not_to_not\ 5/a\ 6 … \ 5a href="cic:/matita/basics/bool/not_eq_true_false.def(3)"\ 6not_eq_true_false\ 5/a\ 6) #H1
+
+(* since by assumption H false is equal to (a==b), by rewriting we obtain the goal
+true=(a==b) that is just the boolean version of H1 *)
+
+ <H @\ 5a href="cic:/matita/basics/logic/sym_eq.def(2)"\ 6sym_eq\ 5/a\ 6 @(\b H1)
+
+(* In the "if" case, we proceed by cases over the boolean equality (a==b); if
+(a==b) is false, the goal is trivial; the other case is absurd, since if (a==b) is
+true, then by reflection a=b, while by hypothesis a≠b *)
-interpretation "in_prl mem" 'mem w l = (in_prl ? l w).
-interpretation "in_prl" 'sem E = (in_prl ? E).
-
-lemma not_epsilon_lp :∀S.∀pi:\ 5a href="cic:/matita/tutorial/chapter4/pitem.ind(1,0,1)"\ 6pitem\ 5/a\ 6 S.\ 5a title="logical not" href="cic:/fakeuri.def(1)"\ 6\neg\ 5/a\ 6(\ 5a title="nil" href="cic:/fakeuri.def(1)"\ 6[\ 5/a\ 6] \ 5a title="in_pl mem" href="cic:/fakeuri.def(1)"\ 6∈\ 5/a\ 6 pi).
-#S #pi (elim pi) normalize / \ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/Not.con(0,1,1)"\ 6nmk\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/
- [#pi1 #pi2 #H1 #H2 % * /\ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/absurd.def(2)"\ 6absurd\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/ * #w1 * #w2 * * #appnil
- cases (\ 5a href="cic:/matita/tutorial/chapter3/nil_to_nil.def(5)"\ 6nil_to_nil\ 5/a\ 6 … appnil) /\ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/absurd.def(2)"\ 6absurd\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/
- |#p11 #p12 #H1 #H2 % * /\ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/absurd.def(2)"\ 6absurd\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/
- |#pi #H % * #w1 * #w2 * * #appnil (cases (\ 5a href="cic:/matita/tutorial/chapter3/nil_to_nil.def(5)"\ 6nil_to_nil\ 5/a\ 6 … appnil)) /\ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/absurd.def(2)"\ 6absurd\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/
+ |cases (\ 5a href="cic:/matita/basics/bool/true_or_false.def(1)"\ 6true_or_false\ 5/a\ 6 (\ 5a href="cic:/matita/tutorial/chapter4/eqb.fix(0,0,3)"\ 6eqb\ 5/a\ 6 ? a b)) // #H1 @\ 5a href="cic:/matita/basics/logic/False_ind.fix(0,1,1)"\ 6False_ind\ 5/a\ 6 @(\ 5a href="cic:/matita/basics/logic/absurd.def(2)"\ 6absurd\ 5/a\ 6 … (\P H1) H)
]
qed.
+
+(* We also introduce two operators "\Pf" and "\bf" to reflect a proof
+of (a==b)=false into a proof of a≠b, and vice-versa *)
+
+notation "\Pf H" non associative with precedence 90
+ for @{(proj1 … (eqb_false ???) $H)}.
-lemma if_true_epsilon: ∀S.∀e:\ 5a href="cic:/matita/tutorial/chapter4/pre.def(1)"\ 6pre\ 5/a\ 6 S. \ 5a title="pair pi2" href="cic:/fakeuri.def(1)"\ 6\snd\ 5/a\ 6 e \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 \ 5a href="cic:/matita/basics/bool/bool.con(0,1,0)"\ 6true\ 5/a\ 6 → (\ 5a title="nil" href="cic:/fakeuri.def(1)"\ 6[\ 5/a\ 6] \ 5a title="in_prl mem" href="cic:/fakeuri.def(1)"\ 6∈\ 5/a\ 6 e).
-#S #e #H %2 >H // qed.
+notation "\bf H" non associative with precedence 90
+ for @{(proj2 … (eqb_false ???) $H)}.
-lemma if_epsilon_true : ∀S.∀e:\ 5a href="cic:/matita/tutorial/chapter4/pre.def(1)"\ 6pre\ 5/a\ 6 S. \ 5a title="nil" href="cic:/fakeuri.def(1)"\ 6[\ 5/a\ 6 ] \ 5a title="in_prl mem" href="cic:/fakeuri.def(1)"\ 6∈\ 5/a\ 6 e → \ 5a title="pair pi2" href="cic:/fakeuri.def(1)"\ 6\snd\ 5/a\ 6 e \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 \ 5a href="cic:/matita/basics/bool/bool.con(0,1,0)"\ 6true\ 5/a\ 6.
-#S * #pi #b * [normalize #abs @\ 5a href="cic:/matita/basics/logic/False_ind.fix(0,1,1)"\ 6False_ind\ 5/a\ 6 /\ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/absurd.def(2)"\ 6absurd\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/] cases b normalize // @\ 5a href="cic:/matita/basics/logic/False_ind.fix(0,1,1)"\ 6False_ind\ 5/a\ 6
+(* The following statement proves that propositional equality in a
+DeqSet is decidable in the traditional sense, namely either a=b or a≠b *)
+
+ lemma dec_eq: ∀S:\ 5a href="cic:/matita/tutorial/chapter4/DeqSet.ind(1,0,0)"\ 6DeqSet\ 5/a\ 6.∀a,b:S. a \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 b \ 5a title="logical or" href="cic:/fakeuri.def(1)"\ 6∨\ 5/a\ 6 a \ 5a title="leibnitz's non-equality" href="cic:/fakeuri.def(1)"\ 6≠\ 5/a\ 6 b.
+#S #a #b cases (\ 5a href="cic:/matita/basics/bool/true_or_false.def(1)"\ 6true_or_false\ 5/a\ 6 (\ 5a href="cic:/matita/tutorial/chapter4/eqb.fix(0,0,3)"\ 6eqb\ 5/a\ 6 ? a b)) #H
+ [%1 @(\P H) | %2 @(\Pf H)]
qed.
-definition lor ≝ λS:\ 5a href="cic:/matita/tutorial/chapter4/Alpha.ind(1,0,0)"\ 6Alpha\ 5/a\ 6.λa,b:\ 5a href="cic:/matita/tutorial/chapter4/pre.def(1)"\ 6pre\ 5/a\ 6 S.\ 5a title="Pair construction" href="cic:/fakeuri.def(1)"\ 6〈\ 5/a\ 6\ 5a title="pair pi1" href="cic:/fakeuri.def(1)"\ 6\fst\ 5/a\ 6 a \ 5a title="por" href="cic:/fakeuri.def(1)"\ 6+\ 5/a\ 6 \ 5a title="pair pi1" href="cic:/fakeuri.def(1)"\ 6\fst\ 5/a\ 6 b,\ 5a title="pair pi2" href="cic:/fakeuri.def(1)"\ 6\snd\ 5/a\ 6 a \ 5a title="boolean or" href="cic:/fakeuri.def(1)"\ 6∨\ 5/a\ 6 \ 5a title="pair pi2" href="cic:/fakeuri.def(1)"\ 6\snd\ 5/a\ 6 b〉.
-
-notation "a ⊕ b" left associative with precedence 60 for @{'oplus $a $b}.
-interpretation "oplus" 'oplus a b = (lor ? a b).
-
-definition item_concat: ∀S:\ 5a href="cic:/matita/tutorial/chapter4/Alpha.ind(1,0,0)"\ 6Alpha\ 5/a\ 6.\ 5a href="cic:/matita/tutorial/chapter4/pitem.ind(1,0,1)"\ 6pitem\ 5/a\ 6 S → \ 5a href="cic:/matita/tutorial/chapter4/pre.def(1)"\ 6pre\ 5/a\ 6 S → \ 5a href="cic:/matita/tutorial/chapter4/pre.def(1)"\ 6pre\ 5/a\ 6 S ≝
- λS,i,e.\ 5a title="Pair construction" href="cic:/fakeuri.def(1)"\ 6〈\ 5/a\ 6i \ 5a title="pcat" href="cic:/fakeuri.def(1)"\ 6·\ 5/a\ 6 \ 5a title="pair pi1" href="cic:/fakeuri.def(1)"\ 6\fst\ 5/a\ 6 e, \ 5a title="pair pi2" href="cic:/fakeuri.def(1)"\ 6\snd\ 5/a\ 6 e〉.
-
-interpretation "item concat" 'concat i e = (item_concat ? i e).
+(*
+\ 5h2 class="section"\ 6Unification Hints\ 5/h2\ 6
+A simple example of a set with a decidable equality is bool. We first define
+the boolean equality beqb, that is just the xand function, then prove that
+beqb b1 b2 is true if and only if b1=b2, and finally build the type DeqBool by
+instantiating the DeqSet record with the previous information *)
+
+definition beqb ≝ λb1,b2.
+ match b1 with [ true ⇒ b2 | false ⇒ \ 5a href="cic:/matita/basics/bool/notb.def(1)"\ 6notb\ 5/a\ 6 b2].
+
+notation < "a == b" non associative with precedence 45 for @{beqb $a $b }.
+
+lemma beqb_true: ∀b1,b2. \ 5a href="cic:/matita/basics/logic/iff.def(1)"\ 6iff\ 5/a\ 6 (\ 5a href="cic:/matita/tutorial/chapter4/beqb.def(2)"\ 6beqb\ 5/a\ 6 b1 b2 \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 \ 5a href="cic:/matita/basics/bool/bool.con(0,1,0)"\ 6true\ 5/a\ 6) (b1 \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 b2).
+#b1 #b2 cases b1 cases b2 normalize /\ 5span class="autotactic"\ 62\ 5span class="autotrace"\ 6 trace \ 5a href="cic:/matita/basics/logic/And.con(0,1,2)"\ 6conj\ 5/a\ 6\ 5/span\ 6\ 5/span\ 6/
+qed.
+
+definition DeqBool ≝ \ 5a href="cic:/matita/tutorial/chapter4/DeqSet.con(0,1,0)"\ 6mk_DeqSet\ 5/a\ 6 \ 5a href="cic:/matita/basics/bool/bool.ind(1,0,0)"\ 6bool\ 5/a\ 6 \ 5a href="cic:/matita/tutorial/chapter4/beqb.def(2)"\ 6beqb\ 5/a\ 6 \ 5a href="cic:/matita/tutorial/chapter4/beqb_true.def(4)"\ 6beqb_true\ 5/a\ 6.
+
+(* At this point, we would expect to be able to prove things like the
+following: for any boolean b, if b==false is true then b=false.
+Unfortunately, this would not work, unless we declare b of type
+DeqBool (change the type in the following statement and see what
+happens). *)
-definition lcat: ∀S:\ 5a href="cic:/matita/tutorial/chapter4/Alpha.ind(1,0,0)"\ 6Alpha\ 5/a\ 6.∀bcast:(∀S:\ 5a href="cic:/matita/tutorial/chapter4/Alpha.ind(1,0,0)"\ 6Alpha\ 5/a\ 6.\ 5a href="cic:/matita/tutorial/chapter4/pre.def(1)"\ 6pre\ 5/a\ 6 S →\ 5a href="cic:/matita/tutorial/chapter4/pre.def(1)"\ 6pre\ 5/a\ 6 S).\ 5a href="cic:/matita/tutorial/chapter4/pre.def(1)"\ 6pre\ 5/a\ 6 S → \ 5a href="cic:/matita/tutorial/chapter4/pre.def(1)"\ 6pre\ 5/a\ 6 S → \ 5a href="cic:/matita/tutorial/chapter4/pre.def(1)"\ 6pre\ 5/a\ 6 S
- ≝ λS,bcast,e1,e2.
- match e1 with [ pair i1 b1 ⇒ if_then_else b1 (i1 \ 5a title="item concat" href="cic:/fakeuri.def(1)"\ 6·\ 5/a\ 6 e2) (i1 ·(bcast S e2)) ]
-].
-
-notation < "a ⊙ b" left associative with precedence 60 for @{'lc $op $a $b}.
-interpretation "lc" 'lc op a b = (lc ? op a b).
-notation > "a ⊙ b" left associative with precedence 60 for @{'lc eclose $a $b}.
-
-ndefinition lk ≝ λS:Alpha.λbcast:∀S:Alpha.∀E:pitem S.pre S.λa:pre S.
- match a with [ mk_pair e1 b1 ⇒
- match b1 with
- [ false ⇒ 〈e1^*, false〉
- | true ⇒ 〈(\fst (bcast ? e1))^*, true〉]].
-
-notation < "a \sup ⊛" non associative with precedence 90 for @{'lk $op $a}.
-interpretation "lk" 'lk op a = (lk ? op a).
-notation > "a^⊛" non associative with precedence 90 for @{'lk eclose $a}.
-
-notation > "•" non associative with precedence 60 for @{eclose ?}.
-nlet rec eclose (S: Alpha) (E: pitem S) on E : pre S ≝
- match E with
- [ pz ⇒ 〈 ∅, false 〉
- | pe ⇒ 〈 ϵ, true 〉
- | ps x ⇒ 〈 `.x, false 〉
- | pp x ⇒ 〈 `.x, false 〉
- | po E1 E2 ⇒ •E1 ⊕ •E2
- | pc E1 E2 ⇒ •E1 ⊙ 〈 E2, false 〉
- | pk E ⇒ 〈(\fst (•E))^*,true〉].
-notation < "• x" non associative with precedence 60 for @{'eclose $x}.
-interpretation "eclose" 'eclose x = (eclose ? x).
-notation > "• x" non associative with precedence 60 for @{'eclose $x}.
-
-ndefinition reclose ≝ λS:Alpha.λp:pre S.let p' ≝ •\fst p in 〈\fst p',\snd p || \snd p'〉.
-interpretation "reclose" 'eclose x = (reclose ? x).
-
-ndefinition eq_f1 ≝ λS.λa,b:word S → Prop.∀w.a w ↔ b w.
-notation > "A =1 B" non associative with precedence 45 for @{'eq_f1 $A $B}.
-notation "A =\sub 1 B" non associative with precedence 45 for @{'eq_f1 $A $B}.
-interpretation "eq f1" 'eq_f1 a b = (eq_f1 ? a b).
-
-naxiom extP : ∀S.∀p,q:word S → Prop.(p =1 q) → p = q.
-
-nlemma epsilon_or : ∀S:Alpha.∀b1,b2. ϵ(b1 || b2) = ϵ b1 ∪ ϵ b2. ##[##2: napply S]
-#S b1 b2; ncases b1; ncases b2; napply extP; #w; nnormalize; @; /2/; *; //; *;
-nqed.
-
-nlemma cupA : ∀S.∀a,b,c:word S → Prop.a ∪ b ∪ c = a ∪ (b ∪ c).
-#S a b c; napply extP; #w; nnormalize; @; *; /3/; *; /3/; nqed.
-
-nlemma cupC : ∀S. ∀a,b:word S → Prop.a ∪ b = b ∪ a.
-#S a b; napply extP; #w; @; *; nnormalize; /2/; nqed.
-
-(* theorem 16: 2 *)
-nlemma oplus_cup : ∀S:Alpha.∀e1,e2:pre S.𝐋\p (e1 ⊕ e2) = 𝐋\p e1 ∪ 𝐋\p e2.
-#S r1; ncases r1; #e1 b1 r2; ncases r2; #e2 b2;
-nwhd in ⊢ (??(??%)?);
-nchange in ⊢(??%?) with (𝐋\p (e1 + e2) ∪ ϵ (b1 || b2));
-nchange in ⊢(??(??%?)?) with (𝐋\p (e1) ∪ 𝐋\p (e2));
-nrewrite > (epsilon_or S …); nrewrite > (cupA S (𝐋\p e1) …);
-nrewrite > (cupC ? (ϵ b1) …); nrewrite < (cupA S (𝐋\p e2) …);
-nrewrite > (cupC ? ? (ϵ b1) …); nrewrite < (cupA …); //;
-nqed.
-
-nlemma odotEt :
- ∀S.∀e1,e2:pitem S.∀b2. 〈e1,true〉 ⊙ 〈e2,b2〉 = 〈e1 · \fst (•e2),b2 || \snd (•e2)〉.
-#S e1 e2 b2; nnormalize; ncases (•e2); //; nqed.
-
-nlemma LcatE : ∀S.∀e1,e2:pitem S.𝐋\p (e1 · e2) = 𝐋\p e1 · 𝐋 |e2| ∪ 𝐋\p e2. //; nqed.
-
-nlemma cup_dotD : ∀S.∀p,q,r:word S → Prop.(p ∪ q) · r = (p · r) ∪ (q · r).
-#S p q r; napply extP; #w; nnormalize; @;
-##[ *; #x; *; #y; *; *; #defw; *; /7/ by or_introl, or_intror, ex_intro, conj;
-##| *; *; #x; *; #y; *; *; /7/ by or_introl, or_intror, ex_intro, conj; ##]
-nqed.
-
-nlemma cup0 :∀S.∀p:word S → Prop.p ∪ {} = p.
-#S p; napply extP; #w; nnormalize; @; /2/; *; //; *; nqed.
-
-nlemma erase_dot : ∀S.∀e1,e2:pitem S.𝐋 |e1 · e2| = 𝐋 |e1| · 𝐋 |e2|.
-#S e1 e2; napply extP; nnormalize; #w; @; *; #w1; *; #w2; *; *; /7/ by ex_intro, conj;
-nqed.
-
-nlemma erase_plus : ∀S.∀e1,e2:pitem S.𝐋 |e1 + e2| = 𝐋 |e1| ∪ 𝐋 |e2|.
-#S e1 e2; napply extP; nnormalize; #w; @; *; /4/ by or_introl, or_intror; nqed.
-
-nlemma erase_star : ∀S.∀e1:pitem S.𝐋 |e1|^* = 𝐋 |e1^*|. //; nqed.
-
-ndefinition substract := λS.λp,q:word S → Prop.λw.p w ∧ ¬ q w.
-interpretation "substract" 'minus a b = (substract ? a b).
-
-nlemma cup_sub: ∀S.∀a,b:word S → Prop. ¬ (a []) → a ∪ (b - {[]}) = (a ∪ b) - {[]}.
-#S a b c; napply extP; #w; nnormalize; @; *; /4/; *; /4/; nqed.
-
-nlemma sub0 : ∀S.∀a:word S → Prop. a - {} = a.
-#S a; napply extP; #w; nnormalize; @; /3/; *; //; nqed.
-
-nlemma subK : ∀S.∀a:word S → Prop. a - a = {}.
-#S a; napply extP; #w; nnormalize; @; *; /2/; nqed.
-
-nlemma subW : ∀S.∀a,b:word S → Prop.∀w.(a - b) w → a w.
-#S a b w; nnormalize; *; //; nqed.
-
-nlemma erase_bull : ∀S.∀a:pitem S. |\fst (•a)| = |a|.
-#S a; nelim a; // by {};
-##[ #e1 e2 IH1 IH2; nchange in ⊢ (???%) with (|e1| · |e2|);
- nrewrite < IH1; nrewrite < IH2;
- nchange in ⊢ (??(??%)?) with (\fst (•e1 ⊙ 〈e2,false〉));
- ncases (•e1); #e3 b; ncases b; nnormalize;
- ##[ ncases (•e2); //; ##| nrewrite > IH2; //]
-##| #e1 e2 IH1 IH2; nchange in ⊢ (???%) with (|e1| + |e2|);
- nrewrite < IH2; nrewrite < IH1;
- nchange in ⊢ (??(??%)?) with (\fst (•e1 ⊕ •e2));
- ncases (•e1); ncases (•e2); //;
-##| #e IH; nchange in ⊢ (???%) with (|e|^* ); nrewrite < IH;
- nchange in ⊢ (??(??%)?) with (\fst (•e))^*; //; ##]
-nqed.
-
-nlemma eta_lp : ∀S.∀p:pre S.𝐋\p p = 𝐋\p 〈\fst p, \snd p〉.
-#S p; ncases p; //; nqed.
-
-nlemma epsilon_dot: ∀S.∀p:word S → Prop. {[]} · p = p.
-#S e; napply extP; #w; nnormalize; @; ##[##2: #Hw; @[]; @w; /3/; ##]
-*; #w1; *; #w2; *; *; #defw defw1 Hw2; nrewrite < defw; nrewrite < defw1;
-napply Hw2; nqed.
-
-(* theorem 16: 1 → 3 *)
-nlemma odot_dot_aux : ∀S.∀e1,e2: pre S.
- 𝐋\p (•(\fst e2)) = 𝐋\p (\fst e2) ∪ 𝐋 |\fst e2| →
- 𝐋\p (e1 ⊙ e2) = 𝐋\p e1 · 𝐋 |\fst e2| ∪ 𝐋\p e2.
-#S e1 e2 th1; ncases e1; #e1' b1'; ncases b1';
-##[ nwhd in ⊢ (??(??%)?); nletin e2' ≝ (\fst e2); nletin b2' ≝ (\snd e2);
- nletin e2'' ≝ (\fst (•(\fst e2))); nletin b2'' ≝ (\snd (•(\fst e2)));
- nchange in ⊢ (??%?) with (?∪?);
- nchange in ⊢ (??(??%?)?) with (?∪?);
- nchange in match (𝐋\p 〈?,?〉) with (?∪?);
- nrewrite > (epsilon_or …); nrewrite > (cupC ? (ϵ ?)…);
- nrewrite > (cupA …);nrewrite < (cupA ?? (ϵ?)…);
- nrewrite > (?: 𝐋\p e2'' ∪ ϵ b2'' = 𝐋\p e2' ∪ 𝐋 |e2'|); ##[##2:
- nchange with (𝐋\p 〈e2'',b2''〉 = 𝐋\p e2' ∪ 𝐋 |e2'|);
- ngeneralize in match th1;
- nrewrite > (eta_lp…); #th1; nrewrite > th1; //;##]
- nrewrite > (eta_lp ? e2);
- nchange in match (𝐋\p 〈\fst e2,?〉) with (𝐋\p e2'∪ ϵ b2');
- nrewrite > (cup_dotD …); nrewrite > (epsilon_dot…);
- nrewrite > (cupC ? (𝐋\p e2')…); nrewrite > (cupA…);nrewrite > (cupA…);
- nrewrite < (erase_bull S e2') in ⊢ (???(??%?)); //;
-##| ncases e2; #e2' b2'; nchange in match (〈e1',false〉⊙?) with 〈?,?〉;
- nchange in match (𝐋\p ?) with (?∪?);
- nchange in match (𝐋\p (e1'·?)) with (?∪?);
- nchange in match (𝐋\p 〈e1',?〉) with (?∪?);
- nrewrite > (cup0…);
- nrewrite > (cupA…); //;##]
-nqed.
-
-nlemma sub_dot_star :
- ∀S.∀X:word S → Prop.∀b. (X - ϵ b) · X^* ∪ {[]} = X^*.
-#S X b; napply extP; #w; @;
-##[ *; ##[##2: nnormalize; #defw; nrewrite < defw; @[]; @; //]
- *; #w1; *; #w2; *; *; #defw sube; *; #lw; *; #flx cj;
- @ (w1 :: lw); nrewrite < defw; nrewrite < flx; @; //;
- @; //; napply (subW … sube);
-##| *; #wl; *; #defw Pwl; nrewrite < defw; nelim wl in Pwl; ##[ #_; @2; //]
- #w' wl' IH; *; #Pw' IHp; nlapply (IH IHp); *;
- ##[ *; #w1; *; #w2; *; *; #defwl' H1 H2;
- @; ncases b in H1; #H1;
- ##[##2: nrewrite > (sub0…); @w'; @(w1@w2);
- nrewrite > (associative_append ? w' w1 w2);
- nrewrite > defwl'; @; ##[@;//] @(wl'); @; //;
- ##| ncases w' in Pw';
- ##[ #ne; @w1; @w2; nrewrite > defwl'; @; //; @; //;
- ##| #x xs Px; @(x::xs); @(w1@w2);
- nrewrite > (defwl'); @; ##[@; //; @; //; @; nnormalize; #; ndestruct]
- @wl'; @; //; ##] ##]
- ##| #wlnil; nchange in match (flatten ? (w'::wl')) with (w' @ flatten ? wl');
- nrewrite < (wlnil); nrewrite > (append_nil…); ncases b;
- ##[ ncases w' in Pw'; /2/; #x xs Pxs; @; @(x::xs); @([]);
- nrewrite > (append_nil…); @; ##[ @; //;@; //; nnormalize; @; #; ndestruct]
- @[]; @; //;
- ##| @; @w'; @[]; nrewrite > (append_nil…); @; ##[##2: @[]; @; //]
- @; //; @; //; @; *;##]##]##]
-nqed.
-
-(* theorem 16: 1 *)
-alias symbol "pc" (instance 13) = "cat lang".
-alias symbol "in_pl" (instance 23) = "in_pl".
-alias symbol "in_pl" (instance 5) = "in_pl".
-alias symbol "eclose" (instance 21) = "eclose".
-ntheorem bull_cup : ∀S:Alpha. ∀e:pitem S. 𝐋\p (•e) = 𝐋\p e ∪ 𝐋 |e|.
-#S e; nelim e; //;
- ##[ #a; napply extP; #w; nnormalize; @; *; /3/ by or_introl, or_intror;
- ##| #a; napply extP; #w; nnormalize; @; *; /3/ by or_introl; *;
- ##| #e1 e2 IH1 IH2;
- nchange in ⊢ (??(??(%))?) with (•e1 ⊙ 〈e2,false〉);
- nrewrite > (odot_dot_aux S (•e1) 〈e2,false〉 IH2);
- nrewrite > (IH1 …); nrewrite > (cup_dotD …);
- nrewrite > (cupA …); nrewrite > (cupC ?? (𝐋\p ?) …);
- nchange in match (𝐋\p 〈?,?〉) with (𝐋\p e2 ∪ {}); nrewrite > (cup0 …);
- nrewrite < (erase_dot …); nrewrite < (cupA …); //;
- ##| #e1 e2 IH1 IH2;
- nchange in match (•(?+?)) with (•e1 ⊕ •e2); nrewrite > (oplus_cup …);
- nrewrite > (IH1 …); nrewrite > (IH2 …); nrewrite > (cupA …);
- nrewrite > (cupC ? (𝐋\p e2)…);nrewrite < (cupA ??? (𝐋\p e2)…);
- nrewrite > (cupC ?? (𝐋\p e2)…); nrewrite < (cupA …);
- nrewrite < (erase_plus …); //.
- ##| #e; nletin e' ≝ (\fst (•e)); nletin b' ≝ (\snd (•e)); #IH;
- nchange in match (𝐋\p ?) with (𝐋\p 〈e'^*,true〉);
- nchange in match (𝐋\p ?) with (𝐋\p (e'^* ) ∪ {[ ]});
- nchange in ⊢ (??(??%?)?) with (𝐋\p e' · 𝐋 |e'|^* );
- nrewrite > (erase_bull…e);
- nrewrite > (erase_star …);
- nrewrite > (?: 𝐋\p e' = 𝐋\p e ∪ (𝐋 |e| - ϵ b')); ##[##2:
- nchange in IH : (??%?) with (𝐋\p e' ∪ ϵ b'); ncases b' in IH;
- ##[ #IH; nrewrite > (cup_sub…); //; nrewrite < IH;
- nrewrite < (cup_sub…); //; nrewrite > (subK…); nrewrite > (cup0…);//;
- ##| nrewrite > (sub0 …); #IH; nrewrite < IH; nrewrite > (cup0 …);//; ##]##]
- nrewrite > (cup_dotD…); nrewrite > (cupA…);
- nrewrite > (?: ((?·?)∪{[]} = 𝐋 |e^*|)); //;
- nchange in match (𝐋 |e^*|) with ((𝐋 |e|)^* ); napply sub_dot_star;##]
- nqed.
-
-(* theorem 16: 3 *)
-nlemma odot_dot:
- ∀S.∀e1,e2: pre S. 𝐋\p (e1 ⊙ e2) = 𝐋\p e1 · 𝐋 |\fst e2| ∪ 𝐋\p e2.
-#S e1 e2; napply odot_dot_aux; napply (bull_cup S (\fst e2)); nqed.
-
-nlemma dot_star_epsilon : ∀S.∀e:re S.𝐋 e · 𝐋 e^* ∪ {[]} = 𝐋 e^*.
-#S e; napply extP; #w; nnormalize; @;
-##[ *; ##[##2: #H; nrewrite < H; @[]; /3/] *; #w1; *; #w2;
- *; *; #defw Hw1; *; #wl; *; #defw2 Hwl; @(w1 :: wl);
- nrewrite < defw; nrewrite < defw2; @; //; @;//;
-##| *; #wl; *; #defw Hwl; ncases wl in defw Hwl; ##[#defw; #; @2; nrewrite < defw; //]
- #x xs defw; *; #Hx Hxs; @; @x; @(flatten ? xs); nrewrite < defw;
- @; /2/; @xs; /2/;##]
- nqed.
-
-nlemma nil_star : ∀S.∀e:re S. [ ] ∈ e^*.
-#S e; @[]; /2/; nqed.
-
-nlemma cupID : ∀S.∀l:word S → Prop.l ∪ l = l.
-#S l; napply extP; #w; @; ##[*]//; #; @; //; nqed.
-
-nlemma cup_star_nil : ∀S.∀l:word S → Prop. l^* ∪ {[]} = l^*.
-#S a; napply extP; #w; @; ##[*; //; #H; nrewrite < H; @[]; @; //] #;@; //;nqed.
-
-nlemma rcanc_sing : ∀S.∀A,C:word S → Prop.∀b:word S .
- ¬ (A b) → A ∪ { (b) } = C → A = C - { (b) }.
-#S A C b nbA defC; nrewrite < defC; napply extP; #w; @;
-##[ #Aw; /3/| *; *; //; #H nH; ncases nH; #abs; nlapply (abs H); *]
-nqed.
-
-(* theorem 16: 4 *)
-nlemma star_dot: ∀S.∀e:pre S. 𝐋\p (e^⊛) = 𝐋\p e · (𝐋 |\fst e|)^*.
-#S p; ncases p; #e b; ncases b;
-##[ nchange in match (〈e,true〉^⊛) with 〈?,?〉;
- nletin e' ≝ (\fst (•e)); nletin b' ≝ (\snd (•e));
- nchange in ⊢ (??%?) with (?∪?);
- nchange in ⊢ (??(??%?)?) with (𝐋\p e' · 𝐋 |e'|^* );
- nrewrite > (?: 𝐋\p e' = 𝐋\p e ∪ (𝐋 |e| - ϵ b' )); ##[##2:
- nlapply (bull_cup ? e); #bc;
- nchange in match (𝐋\p (•e)) in bc with (?∪?);
- nchange in match b' in bc with b';
- ncases b' in bc; ##[##2: nrewrite > (cup0…); nrewrite > (sub0…); //]
- nrewrite > (cup_sub…); ##[napply rcanc_sing] //;##]
- nrewrite > (cup_dotD…); nrewrite > (cupA…);nrewrite > (erase_bull…);
- nrewrite > (sub_dot_star…);
- nchange in match (𝐋\p 〈?,?〉) with (?∪?);
- nrewrite > (cup_dotD…); nrewrite > (epsilon_dot…); //;
-##| nwhd in match (〈e,false〉^⊛); nchange in match (𝐋\p 〈?,?〉) with (?∪?);
- nrewrite > (cup0…);
- nchange in ⊢ (??%?) with (𝐋\p e · 𝐋 |e|^* );
- nrewrite < (cup0 ? (𝐋\p e)); //;##]
-nqed.
-
-nlet rec pre_of_re (S : Alpha) (e : re S) on e : pitem S ≝
- match e with
- [ z ⇒ pz ?
- | e ⇒ pe ?
- | s x ⇒ ps ? x
- | c e1 e2 ⇒ pc ? (pre_of_re ? e1) (pre_of_re ? e2)
- | o e1 e2 ⇒ po ? (pre_of_re ? e1) (pre_of_re ? e2)
- | k e1 ⇒ pk ? (pre_of_re ? e1)].
-
-nlemma notFalse : ¬False. @; //; nqed.
-
-nlemma dot0 : ∀S.∀A:word S → Prop. {} · A = {}.
-#S A; nnormalize; napply extP; #w; @; ##[##2: *]
-*; #w1; *; #w2; *; *; //; nqed.
-
-nlemma Lp_pre_of_re : ∀S.∀e:re S. 𝐋\p (pre_of_re ? e) = {}.
-#S e; nelim e; ##[##1,2,3: //]
-##[ #e1 e2 H1 H2; nchange in match (𝐋\p (pre_of_re S (e1 e2))) with (?∪?);
- nrewrite > H1; nrewrite > H2; nrewrite > (dot0…); nrewrite > (cupID…);//
-##| #e1 e2 H1 H2; nchange in match (𝐋\p (pre_of_re S (e1+e2))) with (?∪?);
- nrewrite > H1; nrewrite > H2; nrewrite > (cupID…); //
-##| #e1 H1; nchange in match (𝐋\p (pre_of_re S (e1^* ))) with (𝐋\p (pre_of_re ??) · ?);
- nrewrite > H1; napply dot0; ##]
-nqed.
-
-nlemma erase_pre_of_reK : ∀S.∀e. 𝐋 |pre_of_re S e| = 𝐋 e.
-#S A; nelim A; //;
-##[ #e1 e2 H1 H2; nchange in match (𝐋 (e1 · e2)) with (𝐋 e1·?);
- nrewrite < H1; nrewrite < H2; //
-##| #e1 e2 H1 H2; nchange in match (𝐋 (e1 + e2)) with (𝐋 e1 ∪ ?);
- nrewrite < H1; nrewrite < H2; //
-##| #e1 H1; nchange in match (𝐋 (e1^* )) with ((𝐋 e1)^* );
- nrewrite < H1; //]
-nqed.
-
-(* corollary 17 *)
-nlemma L_Lp_bull : ∀S.∀e:re S.𝐋 e = 𝐋\p (•pre_of_re ? e).
-#S e; nrewrite > (bull_cup…); nrewrite > (Lp_pre_of_re…);
-nrewrite > (cupC…); nrewrite > (cup0…); nrewrite > (erase_pre_of_reK…); //;
-nqed.
-
-nlemma Pext : ∀S.∀f,g:word S → Prop. f = g → ∀w.f w → g w.
-#S f g H; nrewrite > H; //; nqed.
+example exhint: ∀b:\ 5a href="cic:/matita/tutorial/chapter4/DeqBool.def(5)"\ 6DeqBool\ 5/a\ 6. (b\ 5a title="eqb" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6=\ 5a href="cic:/matita/basics/bool/bool.con(0,2,0)"\ 6false\ 5/a\ 6) \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 \ 5a href="cic:/matita/basics/bool/bool.con(0,1,0)"\ 6true\ 5/a\ 6 → b\ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6\ 5a href="cic:/matita/basics/bool/bool.con(0,2,0)"\ 6false\ 5/a\ 6.
+#b #H @(\P H)
+qed.
+
+(* The point is that == expects in input a pair of objects whose type must be the
+carrier of a DeqSet; bool is indeed the carrier of DeqBool, but the type inference
+system has no knowledge of it (it is an information that has been supplied by the
+user, and stored somewhere in the library). More explicitly, the type inference
+inference system, would face an unification problem consisting to unify bool
+against the carrier of something (a metavaribale) and it has no way to synthetize
+the answer. To solve this kind of situations, matita provides a mechanism to hint
+the system the expected solution. A unification hint is a kind of rule, whose rhd
+is the unification problem, containing some metavariables X1, ..., Xn, and whose
+left hand side is the solution suggested to the system, in the form of equations
+Xi=Mi. The hint is accepted by the system if and only the solution is correct, that
+is, if it is a unifier for the given problem.
+To make an example, in the previous case, the unification problem is bool = carr X,
+and the hint is to take X= mk_DeqSet bool beqb true. The hint is correct, since
+bool is convertible with (carr (mk_DeqSet bool beb true)). *)
+
+unification hint 0 \ 5a href="cic:/fakeuri.def(1)" title="hint_decl_Type1"\ 6≔\ 5/a\ 6 ;
+ X ≟ \ 5a href="cic:/matita/tutorial/chapter4/DeqSet.con(0,1,0)"\ 6mk_DeqSet\ 5/a\ 6 \ 5a href="cic:/matita/basics/bool/bool.ind(1,0,0)"\ 6bool\ 5/a\ 6 \ 5a href="cic:/matita/tutorial/chapter4/beqb.def(2)"\ 6beqb\ 5/a\ 6 \ 5a href="cic:/matita/tutorial/chapter4/beqb_true.def(4)"\ 6beqb_true\ 5/a\ 6
+(* ---------------------------------------- *) ⊢
+ \ 5a href="cic:/matita/basics/bool/bool.ind(1,0,0)"\ 6bool\ 5/a\ 6 ≡ \ 5a href="cic:/matita/tutorial/chapter4/carr.fix(0,0,2)"\ 6carr\ 5/a\ 6 X.
+
+unification hint 0 \ 5a href="cic:/fakeuri.def(1)" title="hint_decl_Type0"\ 6≔\ 5/a\ 6 b1,b2:\ 5a href="cic:/matita/basics/bool/bool.ind(1,0,0)"\ 6bool\ 5/a\ 6;
+ X ≟ \ 5a href="cic:/matita/tutorial/chapter4/DeqSet.con(0,1,0)"\ 6mk_DeqSet\ 5/a\ 6 \ 5a href="cic:/matita/basics/bool/bool.ind(1,0,0)"\ 6bool\ 5/a\ 6 \ 5a href="cic:/matita/tutorial/chapter4/beqb.def(2)"\ 6beqb\ 5/a\ 6 \ 5a href="cic:/matita/tutorial/chapter4/beqb_true.def(4)"\ 6beqb_true\ 5/a\ 6
+(* ---------------------------------------- *) ⊢
+ \ 5a href="cic:/matita/tutorial/chapter4/beqb.def(2)"\ 6beqb\ 5/a\ 6 b1 b2 ≡ \ 5a href="cic:/matita/tutorial/chapter4/eqb.fix(0,0,3)"\ 6eqb\ 5/a\ 6 X b1 b2.
+
+(* After having provided the previous hints, we may rewrite example exhint
+declaring b of type bool. *)
-(* corollary 18 *)
-ntheorem bull_true_epsilon : ∀S.∀e:pitem S. \snd (•e) = true ↔ [ ] ∈ |e|.
-#S e; @;
-##[ #defsnde; nlapply (bull_cup ? e); nchange in match (𝐋\p (•e)) with (?∪?);
- nrewrite > defsnde; #H;
- nlapply (Pext ??? H [ ] ?); ##[ @2; //] *; //;
-
-STOP
-
-notation > "\move term 90 x term 90 E"
-non associative with precedence 60 for @{move ? $x $E}.
-nlet rec move (S: Alpha) (x:S) (E: pitem S) on E : pre S ≝
- match E with
- [ pz ⇒ 〈 ∅, false 〉
- | pe ⇒ 〈 ϵ, false 〉
- | ps y ⇒ 〈 `y, false 〉
- | pp y ⇒ 〈 `y, x == y 〉
- | po e1 e2 ⇒ \move x e1 ⊕ \move x e2
- | pc e1 e2 ⇒ \move x e1 ⊙ \move x e2
- | pk e ⇒ (\move x e)^⊛ ].
-notation < "\move\shy x\shy E" non associative with precedence 60 for @{'move $x $E}.
-notation > "\move term 90 x term 90 E" non associative with precedence 60 for @{'move $x $E}.
-interpretation "move" 'move x E = (move ? x E).
-
-ndefinition rmove ≝ λS:Alpha.λx:S.λe:pre S. \move x (\fst e).
-interpretation "rmove" 'move x E = (rmove ? x E).
-
-nlemma XXz : ∀S:Alpha.∀w:word S. w ∈ ∅ → False.
-#S w abs; ninversion abs; #; ndestruct;
-nqed.
-
-
-nlemma XXe : ∀S:Alpha.∀w:word S. w .∈ ϵ → False.
-#S w abs; ninversion abs; #; ndestruct;
-nqed.
-
-nlemma XXze : ∀S:Alpha.∀w:word S. w .∈ (∅ · ϵ) → False.
-#S w abs; ninversion abs; #; ndestruct; /2/ by XXz,XXe;
-nqed.
-
-
-naxiom in_move_cat:
- ∀S.∀w:word S.∀x.∀E1,E2:pitem S. w .∈ \move x (E1 · E2) →
- (∃w1.∃w2. w = w1@w2 ∧ w1 .∈ \move x E1 ∧ w2 ∈ .|E2|) ∨ w .∈ \move x E2.
-#S w x e1 e2 H; nchange in H with (w .∈ \move x e1 ⊙ \move x e2);
-ncases e1 in H; ncases e2;
-##[##1: *; ##[*; nnormalize; #; ndestruct]
- #H; ninversion H; ##[##1,4,5,6: nnormalize; #; ndestruct]
- nnormalize; #; ndestruct; ncases (?:False); /2/ by XXz,XXze;
-##|##2: *; ##[*; nnormalize; #; ndestruct]
- #H; ninversion H; ##[##1,4,5,6: nnormalize; #; ndestruct]
- nnormalize; #; ndestruct; ncases (?:False); /2/ by XXz,XXze;
-##| #r; *; ##[ *; nnormalize; #; ndestruct]
- #H; ninversion H; ##[##1,4,5,6: nnormalize; #; ndestruct]
- ##[##2: nnormalize; #; ndestruct; @2; @2; //.##]
- nnormalize; #; ndestruct; ncases (?:False); /2/ by XXz;
-##| #y; *; ##[ *; nnormalize; #defw defx; ndestruct; @2; @1; /2/ by conj;##]
- #H; ninversion H; nnormalize; #; ndestruct;
- ##[ncases (?:False); /2/ by XXz] /3/ by or_intror;
-##| #r1 r2; *; ##[ *; #defw]
- ...
-nqed.
-
-ntheorem move_ok:
- ∀S:Alpha.∀E:pre S.∀a,w.w .∈ \move a E ↔ (a :: w) .∈ E.
-#S E; ncases E; #r b; nelim r;
-##[##1,2: #a w; @;
- ##[##1,3: nnormalize; *; ##[##1,3: *; #; ndestruct; ##| #abs; ncases (XXz … abs); ##]
- #H; ninversion H; #; ndestruct;
- ##|##*:nnormalize; *; ##[##1,3: *; #; ndestruct; ##| #H1; ncases (XXz … H1); ##]
- #H; ninversion H; #; ndestruct;##]
-##|#a c w; @; nnormalize; ##[*; ##[*; #; ndestruct; ##] #abs; ninversion abs; #; ndestruct;##]
- *; ##[##2: #abs; ninversion abs; #; ndestruct; ##] *; #; ndestruct;
-##|#a c w; @; nnormalize;
- ##[ *; ##[ *; #defw; nrewrite > defw; #ca; @2; nrewrite > (eqb_t … ca); @; ##]
- #H; ninversion H; #; ndestruct;
- ##| *; ##[ *; #; ndestruct; ##] #H; ninversion H; ##[##2,3,4,5,6: #; ndestruct]
- #d defw defa; ndestruct; @1; @; //; nrewrite > (eqb_true S d d); //. ##]
-##|#r1 r2 H1 H2 a w; @;
- ##[ #H; ncases (in_move_cat … H);
- ##[ *; #w1; *; #w2; *; *; #defw w1m w2m;
- ncases (H1 a w1); #H1w1; #_; nlapply (H1w1 w1m); #good;
- nrewrite > defw; @2; @2 (a::w1); //; ncases good; ##[ *; #; ndestruct] //.
- ##|
- ...
-##|
-##|
-##]
-nqed.
-
-
-notation > "x ↦* E" non associative with precedence 60 for @{move_star ? $x $E}.
-nlet rec move_star (S : decidable) w E on w : bool × (pre S) ≝
- match w with
- [ nil ⇒ E
- | cons x w' ⇒ w' ↦* (x ↦ \snd E)].
-
-ndefinition in_moves ≝ λS:decidable.λw.λE:bool × (pre S). \fst(w ↦* E).
-
-ncoinductive equiv (S:decidable) : bool × (pre S) → bool × (pre S) → Prop ≝
- mk_equiv:
- ∀E1,E2: bool × (pre S).
- \fst E1 = \fst E2 →
- (∀x. equiv S (x ↦ \snd E1) (x ↦ \snd E2)) →
- equiv S E1 E2.
-
-ndefinition NAT: decidable.
- @ nat eqb; /2/.
-nqed.
-
-include "hints_declaration.ma".
-
-alias symbol "hint_decl" (instance 1) = "hint_decl_Type1".
-unification hint 0 ≔ ; X ≟ NAT ⊢ carr X ≡ nat.
-
-ninductive unit: Type[0] ≝ I: unit.
-
-nlet corec foo_nop (b: bool):
- equiv ?
- 〈 b, pc ? (ps ? 0) (pk ? (pc ? (ps ? 1) (ps ? 0))) 〉
- 〈 b, pc ? (pk ? (pc ? (ps ? 0) (ps ? 1))) (ps ? 0) 〉 ≝ ?.
- @; //; #x; ncases x
- [ nnormalize in ⊢ (??%%); napply (foo_nop false)
- | #y; ncases y
- [ nnormalize in ⊢ (??%%); napply (foo_nop false)
- | #w; nnormalize in ⊢ (??%%); napply (foo_nop false) ]##]
-nqed.
-
-(*
-nlet corec foo (a: unit):
- equiv NAT
- (eclose NAT (pc ? (ps ? 0) (pk ? (pc ? (ps ? 1) (ps ? 0)))))
- (eclose NAT (pc ? (pk ? (pc ? (ps ? 0) (ps ? 1))) (ps ? 0)))
-≝ ?.
- @;
- ##[ nnormalize; //
- ##| #x; ncases x
- [ nnormalize in ⊢ (??%%);
- nnormalize in foo: (? → ??%%);
- @; //; #y; ncases y
- [ nnormalize in ⊢ (??%%); napply foo_nop
- | #y; ncases y
- [ nnormalize in ⊢ (??%%);
-
- ##| #z; nnormalize in ⊢ (??%%); napply foo_nop ]##]
- ##| #y; nnormalize in ⊢ (??%%); napply foo_nop
- ##]
-nqed.
-*)
+example exhint1: ∀b:\ 5a href="cic:/matita/basics/bool/bool.ind(1,0,0)"\ 6bool\ 5/a\ 6. (b \ 5a title="eqb" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6= \ 5a href="cic:/matita/basics/bool/bool.con(0,2,0)"\ 6false\ 5/a\ 6) \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 \ 5a href="cic:/matita/basics/bool/bool.con(0,1,0)"\ 6true\ 5/a\ 6 → b \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 \ 5a href="cic:/matita/basics/bool/bool.con(0,2,0)"\ 6false\ 5/a\ 6.
+#b #H @(\P H)
+qed.
-ndefinition test1 : pre ? ≝ ❨ `0 | `1 ❩^* `0.
-ndefinition test2 : pre ? ≝ ❨ (`0`1)^* `0 | (`0`1)^* `1 ❩.
-ndefinition test3 : pre ? ≝ (`0 (`0`1)^* `1)^*.
-
-
-nlemma foo: in_moves ? [0;0;1;0;1;1] (ɛ test3) = true.
- nnormalize in match test3;
- nnormalize;
-//;
-nqed.
-
-(**********************************************************)
-
-ninductive der (S: Type[0]) (a: S) : re S → re S → CProp[0] ≝
- der_z: der S a (z S) (z S)
- | der_e: der S a (e S) (z S)
- | der_s1: der S a (s S a) (e ?)
- | der_s2: ∀b. a ≠ b → der S a (s S b) (z S)
- | der_c1: ∀e1,e2,e1',e2'. in_l S [] e1 → der S a e1 e1' → der S a e2 e2' →
- der S a (c ? e1 e2) (o ? (c ? e1' e2) e2')
- | der_c2: ∀e1,e2,e1'. Not (in_l S [] e1) → der S a e1 e1' →
- der S a (c ? e1 e2) (c ? e1' e2)
- | der_o: ∀e1,e2,e1',e2'. der S a e1 e1' → der S a e2 e2' →
- der S a (o ? e1 e2) (o ? e1' e2').
-
-nlemma eq_rect_CProp0_r:
- ∀A.∀a,x.∀p:eq ? x a.∀P: ∀x:A. eq ? x a → CProp[0]. P a (refl A a) → P x p.
- #A; #a; #x; #p; ncases p; #P; #H; nassumption.
-nqed.
-
-nlemma append1: ∀A.∀a:A.∀l. [a] @ l = a::l. //. nqed.
-
-naxiom in_l1: ∀S,r1,r2,w. in_l S [ ] r1 → in_l S w r2 → in_l S w (c S r1 r2).
-(* #S; #r1; #r2; #w; nelim r1
- [ #K; ninversion K
- | #H1; #H2; napply (in_c ? []); //
- | (* tutti casi assurdi *) *)
-
-ninductive in_l' (S: Type[0]) : word S → re S → CProp[0] ≝
- in_l_empty1: ∀E.in_l S [] E → in_l' S [] E
- | in_l_cons: ∀a,w,e,e'. in_l' S w e' → der S a e e' → in_l' S (a::w) e.
-
-ncoinductive eq_re (S: Type[0]) : re S → re S → CProp[0] ≝
- mk_eq_re: ∀E1,E2.
- (in_l S [] E1 → in_l S [] E2) →
- (in_l S [] E2 → in_l S [] E1) →
- (∀a,E1',E2'. der S a E1 E1' → der S a E2 E2' → eq_re S E1' E2') →
- eq_re S E1 E2.
-
-(* serve il lemma dopo? *)
-ntheorem eq_re_is_eq: ∀S.∀E1,E2. eq_re S E1 E2 → ∀w. in_l ? w E1 → in_l ? w E2.
- #S; #E1; #E2; #H1; #w; #H2; nelim H2 in E2 H1 ⊢ %
- [ #r; #K (* ok *)
- | #a; #w; #R1; #R2; #K1; #K2; #K3; #R3; #K4; @2 R2; //; ncases K4;
-
-(* IL VICEVERSA NON VALE *)
-naxiom in_l_to_in_l: ∀S,w,E. in_l' S w E → in_l S w E.
-(* #S; #w; #E; #H; nelim H
- [ //
- | #a; #w'; #r; #r'; #H1; (* e si cade qua sotto! *)
+(* The cartesian product of two DeqSets is still a DeqSet. To prove
+this, we must as usual define the boolen equality function, and prove
+it correctly reflects propositional equality. *)
+
+definition eq_pairs ≝
+ λA,B:\ 5a href="cic:/matita/tutorial/chapter4/DeqSet.ind(1,0,0)"\ 6DeqSet\ 5/a\ 6.λp1,p2:A\ 5a title="Product" href="cic:/fakeuri.def(1)"\ 6×\ 5/a\ 6B.(\ 5a title="pair pi1" href="cic:/fakeuri.def(1)"\ 6\fst\ 5/a\ 6 p1 \ 5a title="eqb" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6= \ 5a title="pair pi1" href="cic:/fakeuri.def(1)"\ 6\fst\ 5/a\ 6 p2) \ 5a title="boolean and" href="cic:/fakeuri.def(1)"\ 6∧\ 5/a\ 6 (\ 5a title="pair pi2" href="cic:/fakeuri.def(1)"\ 6\snd\ 5/a\ 6 p1 \ 5a title="eqb" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6= \ 5a title="pair pi2" href="cic:/fakeuri.def(1)"\ 6\snd\ 5/a\ 6 p2).
+
+lemma eq_pairs_true: ∀A,B:\ 5a href="cic:/matita/tutorial/chapter4/DeqSet.ind(1,0,0)"\ 6DeqSet\ 5/a\ 6.∀p1,p2:A\ 5a title="Product" href="cic:/fakeuri.def(1)"\ 6×\ 5/a\ 6B.
+ \ 5a href="cic:/matita/tutorial/chapter4/eq_pairs.def(4)"\ 6eq_pairs\ 5/a\ 6 A B p1 p2 \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 \ 5a href="cic:/matita/basics/bool/bool.con(0,1,0)"\ 6true\ 5/a\ 6 \ 5a title="iff" href="cic:/fakeuri.def(1)"\ 6↔\ 5/a\ 6 p1 \ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6 p2.
+#A #B * #a1 #b1 * #a2 #b2 %
+ [#H cases (\ 5a href="cic:/matita/basics/bool/andb_true.def(5)"\ 6andb_true\ 5/a\ 6 …H) normalize #eqa #eqb >(\P eqa) >(\P eqb) //
+ |#H destruct normalize >(\b (\ 5a href="cic:/matita/basics/logic/eq.con(0,1,2)"\ 6refl\ 5/a\ 6 … a2)) >(\b (\ 5a href="cic:/matita/basics/logic/eq.con(0,1,2)"\ 6refl\ 5/a\ 6 … b2)) //
]
-nqed. *)
-
-ntheorem der1: ∀S,a,e,e',w. der S a e e' → in_l S w e' → in_l S (a::w) e.
- #S; #a; #E; #E'; #w; #H; nelim H
- [##1,2: #H1; ninversion H1
- [##1,8: #_; #K; (* non va ndestruct K; *) ncases (?:False); (* perche' due goal?*) /2/
- |##2,9: #X; #Y; #K; ncases (?:False); /2/
- |##3,10: #x; #y; #z; #w; #a; #b; #c; #d; #e; #K; ncases (?:False); /2/
- |##4,11: #x; #y; #z; #w; #a; #b; #K; ncases (?:False); /2/
- |##5,12: #x; #y; #z; #w; #a; #b; #K; ncases (?:False); /2/
- |##6,13: #x; #y; #K; ncases (?:False); /2/
- |##7,14: #x; #y; #z; #w; #a; #b; #c; #d; #K; ncases (?:False); /2/]
-##| #H1; ninversion H1
- [ //
- | #X; #Y; #K; ncases (?:False); /2/
- | #x; #y; #z; #w; #a; #b; #c; #d; #e; #K; ncases (?:False); /2/
- | #x; #y; #z; #w; #a; #b; #K; ncases (?:False); /2/
- | #x; #y; #z; #w; #a; #b; #K; ncases (?:False); /2/
- | #x; #y; #K; ncases (?:False); /2/
- | #x; #y; #z; #w; #a; #b; #c; #d; #K; ncases (?:False); /2/ ]
-##| #H1; #H2; #H3; ninversion H3
- [ #_; #K; ncases (?:False); /2/
- | #X; #Y; #K; ncases (?:False); /2/
- | #x; #y; #z; #w; #a; #b; #c; #d; #e; #K; ncases (?:False); /2/
- | #x; #y; #z; #w; #a; #b; #K; ncases (?:False); /2/
- | #x; #y; #z; #w; #a; #b; #K; ncases (?:False); /2/
- | #x; #y; #K; ncases (?:False); /2/
- | #x; #y; #z; #w; #a; #b; #c; #d; #K; ncases (?:False); /2/ ]
-##| #r1; #r2; #r1'; #r2'; #H1; #H2; #H3; #H4; #H5; #H6;
\ No newline at end of file
+qed.
+
+definition DeqProd ≝ λA,B:\ 5a href="cic:/matita/tutorial/chapter4/DeqSet.ind(1,0,0)"\ 6DeqSet\ 5/a\ 6.
+ \ 5a href="cic:/matita/tutorial/chapter4/DeqSet.con(0,1,0)"\ 6mk_DeqSet\ 5/a\ 6 (A\ 5a title="Product" href="cic:/fakeuri.def(1)"\ 6×\ 5/a\ 6B) (\ 5a href="cic:/matita/tutorial/chapter4/eq_pairs.def(4)"\ 6eq_pairs\ 5/a\ 6 A B) (\ 5a href="cic:/matita/tutorial/chapter4/eq_pairs_true.def(6)"\ 6eq_pairs_true\ 5/a\ 6 A B).
+
+(* Having an unification problem of the kind T1×T2 = carr X, what kind
+of hint can we give to the system? We expect T1 to be the carrier of a
+DeqSet C1, T2 to be the carrier of a DeqSet C2, and X to be DeqProd C1 C2.
+This is expressed by the following hint: *)
+
+unification hint 0 \ 5a href="cic:/fakeuri.def(1)" title="hint_decl_Type1"\ 6≔\ 5/a\ 6 C1,C2;
+ T1 ≟ \ 5a href="cic:/matita/tutorial/chapter4/carr.fix(0,0,2)"\ 6carr\ 5/a\ 6 C1,
+ T2 ≟ \ 5a href="cic:/matita/tutorial/chapter4/carr.fix(0,0,2)"\ 6carr\ 5/a\ 6 C2,
+ X ≟ \ 5a href="cic:/matita/tutorial/chapter4/DeqProd.def(7)"\ 6DeqProd\ 5/a\ 6 C1 C2
+(* ---------------------------------------- *) ⊢
+ T1\ 5a title="Product" href="cic:/fakeuri.def(1)"\ 6×\ 5/a\ 6T2 ≡ \ 5a href="cic:/matita/tutorial/chapter4/carr.fix(0,0,2)"\ 6carr\ 5/a\ 6 X.
+
+unification hint 0 \ 5a href="cic:/fakeuri.def(1)" title="hint_decl_Type0"\ 6≔\ 5/a\ 6 T1,T2,p1,p2;
+ X ≟ \ 5a href="cic:/matita/tutorial/chapter4/DeqProd.def(7)"\ 6DeqProd\ 5/a\ 6 T1 T2
+(* ---------------------------------------- *) ⊢
+ \ 5a href="cic:/matita/tutorial/chapter4/eq_pairs.def(4)"\ 6eq_pairs\ 5/a\ 6 T1 T2 p1 p2 ≡ \ 5a href="cic:/matita/tutorial/chapter4/eqb.fix(0,0,3)"\ 6eqb\ 5/a\ 6 X p1 p2.
+
+example hint2: ∀b1,b2.
+ \ 5a title="Pair construction" href="cic:/fakeuri.def(1)"\ 6〈\ 5/a\ 6b1,\ 5a href="cic:/matita/basics/bool/bool.con(0,1,0)"\ 6true\ 5/a\ 6〉\ 5a title="eqb" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6=\ 5a title="Pair construction" href="cic:/fakeuri.def(1)"\ 6〈\ 5/a\ 6\ 5a href="cic:/matita/basics/bool/bool.con(0,2,0)"\ 6false\ 5/a\ 6,b2〉\ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6\ 5a href="cic:/matita/basics/bool/bool.con(0,1,0)"\ 6true\ 5/a\ 6 → \ 5a title="Pair construction" href="cic:/fakeuri.def(1)"\ 6〈\ 5/a\ 6b1,\ 5a href="cic:/matita/basics/bool/bool.con(0,1,0)"\ 6true\ 5/a\ 6〉\ 5a title="leibnitz's equality" href="cic:/fakeuri.def(1)"\ 6=\ 5/a\ 6\ 5a title="Pair construction" href="cic:/fakeuri.def(1)"\ 6〈\ 5/a\ 6\ 5a href="cic:/matita/basics/bool/bool.con(0,2,0)"\ 6false\ 5/a\ 6,b2〉.
+#b1 #b2 #H @(\P H).
\ No newline at end of file
projects / helm.git / blobdiff