set "baseuri" "cic:/matita/nat/compare".
-include "nat/orders.ma".
include "datatypes/bool.ma".
include "datatypes/compare.ma".
+include "nat/orders.ma".
let rec eqb n m \def
match n with
theorem eqb_to_Prop: \forall n,m:nat.
match (eqb n m) with
[ true \Rightarrow n = m
-| false \Rightarrow \lnot (n = m)].
+| false \Rightarrow n \neq m].
intros.
apply nat_elim2
(\lambda n,m:nat.match (eqb n m) with
[ true \Rightarrow n = m
-| false \Rightarrow \lnot (n = m)]).
+| false \Rightarrow n \neq m]).
intro.elim n1.
simplify.reflexivity.
simplify.apply not_eq_O_S.
intro.
simplify.
-intro. apply not_eq_O_S n1 ?.apply sym_eq.assumption.
+intro. apply not_eq_O_S n1.apply sym_eq.assumption.
intros.simplify.
generalize in match H.
elim (eqb n1 m1).
qed.
theorem eqb_elim : \forall n,m:nat.\forall P:bool \to Prop.
-(n=m \to (P true)) \to (\lnot n=m \to (P false)) \to (P (eqb n m)).
+(n=m \to (P true)) \to (n \neq m \to (P false)) \to (P (eqb n m)).
intros.
cut
match (eqb n m) with
[ true \Rightarrow n = m
-| false \Rightarrow \lnot (n = m)] \to (P (eqb n m)).
+| false \Rightarrow n \neq m] \to (P (eqb n m)).
apply Hcut.apply eqb_to_Prop.
elim eqb n m.
apply (H H2).
apply (H1 H2).
qed.
+theorem eqb_n_n: \forall n. eqb n n = true.
+intro.elim n.simplify.reflexivity.
+simplify.assumption.
+qed.
+
+theorem eq_to_eqb_true: \forall n,m:nat.
+n = m \to eqb n m = true.
+intros.apply eqb_elim n m.
+intros. reflexivity.
+intros.apply False_ind.apply H1 H.
+qed.
+
+theorem not_eq_to_eqb_false: \forall n,m:nat.
+\lnot (n = m) \to eqb n m = false.
+intros.apply eqb_elim n m.
+intros. apply False_ind.apply H H1.
+intros.reflexivity.
+qed.
+
let rec leb n m \def
match n with
[ O \Rightarrow true
theorem leb_to_Prop: \forall n,m:nat.
match (leb n m) with
[ true \Rightarrow n \leq m
-| false \Rightarrow \lnot (n \leq m)].
+| false \Rightarrow n \nleq m].
intros.
apply nat_elim2
(\lambda n,m:nat.match (leb n m) with
[ true \Rightarrow n \leq m
-| false \Rightarrow \lnot (n \leq m)]).
+| false \Rightarrow n \nleq m]).
simplify.exact le_O_n.
simplify.exact not_le_Sn_O.
intros 2.simplify.elim (leb n1 m1).
qed.
theorem leb_elim: \forall n,m:nat. \forall P:bool \to Prop.
-(n \leq m \to (P true)) \to (\not (n \leq m) \to (P false)) \to
+(n \leq m \to (P true)) \to (n \nleq m \to (P false)) \to
P (leb n m).
intros.
cut
match (leb n m) with
[ true \Rightarrow n \leq m
-| false \Rightarrow \lnot (n \leq m)] \to (P (leb n m)).
+| false \Rightarrow n \nleq m] \to (P (leb n m)).
apply Hcut.apply leb_to_Prop.
elim leb n m.
apply (H H2).
intro.simplify.apply le_S_S. apply le_O_n.
intros 2.simplify.elim (nat_compare n1 m1).
simplify. apply le_S_S.apply H.
-simplify. apply le_S_S.apply H.
simplify. apply eq_f. apply H.
+simplify. apply le_S_S.apply H.
qed.
theorem nat_compare_n_m_m_n: \forall n,m:nat.
apply Hcut.apply nat_compare_to_Prop.
elim (nat_compare n m).
apply (H H3).
-apply (H2 H3).
apply (H1 H3).
+apply (H2 H3).
qed.