(* *)
(**************************************************************************)
-include "ground_2/notation/constructors/successor_1.ma".
-include "ground_2/notation/functions/predecessor_1.ma".
+include "ground_2/notation/functions/uparrow_1.ma".
+include "ground_2/notation/functions/downarrow_1.ma".
include "arithmetics/nat.ma".
include "ground_2/lib/relations.ma".
(* ARITHMETICAL PROPERTIES **************************************************)
-interpretation "nat successor" 'Successor m = (S m).
+interpretation "nat successor" 'UpArrow m = (S m).
-interpretation "nat predecessor" 'Predecessor m = (pred m).
+interpretation "nat predecessor" 'DownArrow m = (pred m).
interpretation "nat min" 'and x y = (min x y).
lemma pred_S: ∀m. pred (S m) = m.
// qed.
-lemma plus_S1: â\88\80x,y. ⫯(x+y) = (⫯x) + y.
+lemma plus_S1: â\88\80x,y. â\86\91(x+y) = (â\86\91x) + y.
// qed.
lemma max_O1: ∀n. n = (0 ∨ n).
lemma max_O2: ∀n. n = (n ∨ 0).
// qed.
-lemma max_SS: â\88\80n1,n2. ⫯(n1â\88¨n2) = (⫯n1 â\88¨ ⫯n2).
+lemma max_SS: â\88\80n1,n2. â\86\91(n1â\88¨n2) = (â\86\91n1 â\88¨ â\86\91n2).
#n1 #n2 elim (decidable_le n1 n2) #H normalize
[ >(le_to_leb_true … H) | >(not_le_to_leb_false … H) ] -H //
qed.
(* Equations ****************************************************************)
-lemma plus_SO: â\88\80n. n + 1 = ⫯n.
+lemma plus_SO: â\88\80n. n + 1 = â\86\91n.
// qed.
lemma minus_plus_m_m_commutative: ∀n,m:nat. n = m + n - m.
#x #z #y #Hzy #Hyx >plus_minus // >commutative_plus >plus_minus //
qed-.
+lemma lt_succ_pred: ∀m,n. n < m → m = ↑↓m.
+#m #n #Hm >S_pred /2 width=2 by ltn_to_ltO/
+qed-.
+
fact plus_minus_minus_be_aux: ∀i,x,y,z. y ≤ z → z ≤ x → i = z - y → x - z + i = x - y.
/2 width=1 by plus_minus_minus_be/ qed-.
@le_S_S_to_le >S_pred /2 width=3 by transitive_lt/
qed.
-lemma lt_S_S: â\88\80x,y. x < y â\86\92 ⫯x < ⫯y.
+lemma lt_S_S: â\88\80x,y. x < y â\86\92 â\86\91x < â\86\91y.
/2 width=1 by le_S_S/ qed.
-lemma lt_S: â\88\80n,m. n < m â\86\92 n < ⫯m.
+lemma lt_S: â\88\80n,m. n < m â\86\92 n < â\86\91m.
/2 width=1 by le_S/ qed.
-lemma max_S1_le_S: â\88\80n1,n2,n. (n1 â\88¨ n2) â\89¤ n â\86\92 (⫯n1 â\88¨ n2) â\89¤ ⫯n.
+lemma max_S1_le_S: â\88\80n1,n2,n. (n1 â\88¨ n2) â\89¤ n â\86\92 (â\86\91n1 â\88¨ n2) â\89¤ â\86\91n.
/4 width=2 by to_max, le_maxr, le_S_S, le_S/ qed-.
-lemma max_S2_le_S: â\88\80n1,n2,n. (n1 â\88¨ n2) â\89¤ n â\86\92 (n1 â\88¨ ⫯n2) â\89¤ ⫯n.
+lemma max_S2_le_S: â\88\80n1,n2,n. (n1 â\88¨ n2) â\89¤ n â\86\92 (n1 â\88¨ â\86\91n2) â\89¤ â\86\91n.
/2 width=1 by max_S1_le_S/ qed-.
lemma arith_j: ∀x,y,z. x-y-1 ≤ x-(y-z)-1.
lemma lt_le_false: ∀x,y. x < y → y ≤ x → ⊥.
/3 width=4 by lt_refl_false, lt_to_le_to_lt/ qed-.
-lemma succ_inv_refl_sn: â\88\80x. ⫯x = x → ⊥.
-#x #H @(lt_le_false x (⫯x)) //
+lemma succ_inv_refl_sn: â\88\80x. â\86\91x = x → ⊥.
+#x #H @(lt_le_false x (â\86\91x)) //
qed-.
lemma le_plus_xSy_O_false: ∀x,y. x + S y ≤ 0 → ⊥.
/2 width=2 by le_plus_to_le/
qed-.
-lemma lt_S_S_to_lt: â\88\80x,y. ⫯x < ⫯y → x < y.
+lemma lt_S_S_to_lt: â\88\80x,y. â\86\91x < â\86\91y → x < y.
/2 width=1 by le_S_S_to_le/ qed-.
(* Note this should go in nat.ma *)
#H destruct
qed-.
-lemma lt_inv_O1: â\88\80n. 0 < n â\86\92 â\88\83m. ⫯m = n.
+lemma lt_inv_O1: â\88\80n. 0 < n â\86\92 â\88\83m. â\86\91m = n.
* /2 width=2 by ex_intro/
#H cases (lt_le_false … H) -H //
qed-.
-lemma lt_inv_S1: â\88\80m,n. ⫯m < n â\86\92 â\88\83â\88\83p. m < p & ⫯p = n.
+lemma lt_inv_S1: â\88\80m,n. â\86\91m < n â\86\92 â\88\83â\88\83p. m < p & â\86\91p = n.
#m * /3 width=3 by lt_S_S_to_lt, ex2_intro/
#H cases (lt_le_false … H) -H //
qed-.
-lemma lt_inv_gen: â\88\80y,x. x < y â\86\92 â\88\83â\88\83z. x â\89¤ z & ⫯z = y.
+lemma lt_inv_gen: â\88\80y,x. x < y â\86\92 â\88\83â\88\83z. x â\89¤ z & â\86\91z = y.
* /3 width=3 by le_S_S_to_le, ex2_intro/
#x #H elim (lt_le_false … H) -H //
qed-.
lemma plus_inv_O3: ∀x,y. x + y = 0 → x = 0 ∧ y = 0.
/2 width=1 by plus_le_0/ qed-.
+lemma plus_inv_S3_sn: ∀x1,x2,x3. x1+x2 = ↑x3 →
+ ∨∨ ∧∧ x1 = 0 & x2 = ↑x3
+ | ∃∃y1. x1 = ↑y1 & y1 + x2 = x3.
+* /3 width=1 by or_introl, conj/
+#x1 #x2 #x3 <plus_S1 #H destruct
+/3 width=3 by ex2_intro, or_intror/
+qed-.
+
+lemma plus_inv_S3_dx: ∀x2,x1,x3. x1+x2 = ↑x3 →
+ ∨∨ ∧∧ x2 = 0 & x1 = ↑x3
+ | ∃∃y2. x2 = ↑y2 & x1 + y2 = x3.
+* /3 width=1 by or_introl, conj/
+#x2 #x1 #x3 <plus_n_Sm #H destruct
+/3 width=3 by ex2_intro, or_intror/
+qed-.
+
lemma max_inv_O3: ∀x,y. (x ∨ y) = 0 → 0 = x ∧ 0 = y.
/4 width=2 by le_maxr, le_maxl, le_n_O_to_eq, conj/
qed-.
* /2 width=1 by conj/ #x #y normalize #H destruct
qed-.
-lemma nat_split: â\88\80x. x = 0 â\88¨ â\88\83y. ⫯y = x.
+lemma nat_split: â\88\80x. x = 0 â\88¨ â\88\83y. â\86\91y = x.
* /3 width=2 by ex_intro, or_introl, or_intror/
qed-.
lemma lt_elim: ∀R:relation nat.
- (â\88\80n2. R O (⫯n2)) →
- (â\88\80n1,n2. R n1 n2 â\86\92 R (⫯n1) (⫯n2)) →
+ (â\88\80n2. R O (â\86\91n2)) →
+ (â\88\80n1,n2. R n1 n2 â\86\92 R (â\86\91n1) (â\86\91n2)) →
∀n2,n1. n1 < n2 → R n1 n2.
#R #IH1 #IH2 #n2 elim n2 -n2
[ #n1 #H elim (lt_le_false … H) -H //
lemma le_elim: ∀R:relation nat.
(∀n2. R O (n2)) →
- (â\88\80n1,n2. R n1 n2 â\86\92 R (⫯n1) (⫯n2)) →
+ (â\88\80n1,n2. R n1 n2 â\86\92 R (â\86\91n1) (â\86\91n2)) →
∀n1,n2. n1 ≤ n2 → R n1 n2.
#R #IH1 #IH2 #n1 #n2 @(nat_elim2 … n1 n2) -n1 -n2
/4 width=1 by monotonic_pred/ -IH1 -IH2