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Thomas Baruchel 2023-01-12 18:18:17 +01:00
parent 6d85df3fbc
commit 6d0ee965ba

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@ -327,7 +327,6 @@ Proof.
Qed.
(**
New following lemmas and theorems are related to the size
of squares in the Thue-Morse sequence, namely lengths of
@ -605,6 +604,148 @@ Proof.
generalize H2. apply IHj. easy.
Qed.
(**
This section contains lemmas and theorems related to the length of the
prefix being odd or even in front of a squared pattern.
*)
Lemma tm_step_odd_prefix_square_1 : forall (n : nat) (hd a tl : list bool),
tm_step n = hd ++ a ++ a ++ tl
-> length a = 1 -> even (length hd) = false.
Proof.
intros n hd a tl. intros H I.
assert (J: Nat.even (length hd) || Nat.odd (length hd) = true).
apply Nat.orb_even_odd. apply orb_prop in J. destruct J.
- assert (K: count_occ Bool.bool_dec hd true
= count_occ Bool.bool_dec hd false).
generalize H0. generalize H. apply tm_step_count_occ.
assert (L: even (length (hd ++ a ++ a)) = true).
rewrite app_length. rewrite app_length. rewrite I.
rewrite Nat.even_add_even. assumption. rewrite Nat.add_1_r.
apply Nat.EvenT_Even. apply Nat.even_EvenT. easy.
assert (M: count_occ Bool.bool_dec (hd ++ a ++ a) true
= count_occ Bool.bool_dec (hd ++ a ++ a) false).
generalize L. generalize H.
replace (hd ++ a ++ a ++ tl) with ((hd ++ a ++ a) ++ tl).
apply tm_step_count_occ.
rewrite <- app_assoc. apply app_inv_head_iff.
rewrite <- app_assoc. reflexivity.
rewrite count_occ_app in M. symmetry in M.
rewrite count_occ_app in M. rewrite K in M.
rewrite Nat.add_cancel_l in M. destruct a.
+ inversion I.
+ destruct b; simpl in I; apply Nat.succ_inj in I;
rewrite length_zero_iff_nil in I; rewrite I in M;
simpl in M; inversion M.
- rewrite <- Nat.negb_odd. rewrite H0. reflexivity.
Qed.
Lemma tm_step_odd_prefix_square_3 : forall (n : nat) (hd a tl : list bool),
tm_step n = hd ++ a ++ a ++ tl
-> length a = 3 -> even (length hd) = false.
Proof.
intros n hd a tl. intros H I.
assert (J: Nat.even (length hd) || Nat.odd (length hd) = true).
apply Nat.orb_even_odd. apply orb_prop in J. destruct J.
assert (Z: a = [true;false;true] \/ a = [false;true;false]).
destruct a. inversion I. destruct a. inversion I.
destruct a. inversion I. destruct a.
- destruct b; destruct b0; destruct b1.
+ replace ([true;true;true] ++ [true;true;true] ++ tl)
with ([true;true] ++ [true] ++ [true;true] ++ [true] ++ tl) in H.
apply tm_step_consecutive_identical in H. inversion H.
reflexivity.
+ replace ([true;true;false] ++ [true;true;false] ++ tl)
with ([true;true] ++ [false] ++ [true;true] ++ [false] ++ tl) in H.
apply tm_step_consecutive_identical in H. inversion H.
reflexivity.
+ left. reflexivity.
+ replace (hd ++ [true;false;false] ++ [true;false;false] ++ tl)
with ((hd ++ [true]) ++ [false; false] ++ [true] ++ [false;false] ++ tl) in H.
apply tm_step_consecutive_identical in H. inversion H.
rewrite <- app_assoc. reflexivity.
+ replace (hd ++ [false;true;true] ++ [false;true;true] ++ tl)
with ((hd ++ [false]) ++ [true; true] ++ [false] ++ [true;true] ++ tl) in H.
apply tm_step_consecutive_identical in H. inversion H.
rewrite <- app_assoc. reflexivity.
+ right. reflexivity.
+ replace ([false;false;true] ++ [false;false;true] ++ tl)
with ([false;false] ++ [true] ++ [false;false] ++ [true] ++ tl) in H.
apply tm_step_consecutive_identical in H. inversion H.
reflexivity.
+ replace ([false;false;false] ++ [false;false;false] ++ tl)
with ([false;false] ++ [false] ++ [false;false] ++ [false] ++ tl) in H.
apply tm_step_consecutive_identical in H. inversion H.
reflexivity.
- inversion I.
- assert (K: count_occ Bool.bool_dec hd true
= count_occ Bool.bool_dec hd false).
generalize H0. generalize H. apply tm_step_count_occ.
destruct Z; rewrite H1 in H.
replace (hd ++ [true;false;true] ++ [true;false;true] ++ tl)
with ((hd ++ [true;false;true;true]) ++ [false;true] ++ tl) in H.
assert (even (length (hd ++ [true;false;true;true])) = true).
rewrite app_length. rewrite Nat.even_add. rewrite H0. reflexivity.
assert (M: count_occ Bool.bool_dec (hd ++ [true;false;true;true]) true
= count_occ Bool.bool_dec (hd ++ [true;false;true;true]) false).
generalize H2. generalize H. apply tm_step_count_occ.
rewrite count_occ_app in M. symmetry in M. rewrite count_occ_app in M.
rewrite K in M. rewrite Nat.add_cancel_l in M. inversion M.
rewrite <- app_assoc. reflexivity.
replace (hd ++ [false;true;false] ++ [false;true;false] ++ tl)
with ((hd ++ [false;true;false;false]) ++ [true;false] ++ tl) in H.
assert (even (length (hd ++ [false;true;false;false])) = true).
rewrite app_length. rewrite Nat.even_add. rewrite H0. reflexivity.
assert (M: count_occ Bool.bool_dec (hd ++ [false;true;false;false]) true
= count_occ Bool.bool_dec (hd ++ [false;true;false;false]) false).
generalize H2. generalize H. apply tm_step_count_occ.
rewrite count_occ_app in M. symmetry in M. rewrite count_occ_app in M.
rewrite K in M. rewrite Nat.add_cancel_l in M. inversion M.
rewrite <- app_assoc. reflexivity.
- rewrite <- Nat.negb_odd. rewrite H0. reflexivity.
Qed.
Lemma tm_step_odd_prefix_square : forall (n : nat) (hd a tl : list bool),
tm_step n = hd ++ a ++ a ++ tl
-> odd (length a) = true -> even (length hd) = false.
Proof.
intros n hd a tl. intros H I.
assert (length a < 4).
generalize I. generalize H. apply tm_step_odd_square.
destruct a. inversion I.
destruct a.
apply tm_step_odd_prefix_square_1 with (n := n) (a := [b]) (tl := tl).
assumption. reflexivity.
destruct a. inversion I.
destruct a.
apply tm_step_odd_prefix_square_3 with (n := n) (a := [b;b0;b1]) (tl := tl).
assumption. reflexivity.
simpl in H0.
rewrite <- Nat.succ_lt_mono in H0.
rewrite <- Nat.succ_lt_mono in H0.
rewrite <- Nat.succ_lt_mono in H0.
rewrite <- Nat.succ_lt_mono in H0.
apply Nat.nlt_0_r in H0. contradiction H0.
Qed.
Theorem tm_step_square_pos_even : forall (n : nat) (hd a tl : list bool),
tm_step n = hd ++ a ++ a ++ tl
-> 0 < length a -> even (length (hd ++ a)) = true.
Proof.
intros n hd a tl. intros H I.
rewrite app_length. rewrite Nat.even_add.
assert (J: Nat.even (length a) || Nat.odd (length a) = true).
apply Nat.orb_even_odd. apply orb_prop in J. destruct J.
- rewrite H0.