Commit 239cb4cf authored by Jacques-Henri Jourdan's avatar Jacques-Henri Jourdan

A few lemmas about vec and fin.

parent aec7c174
......@@ -78,10 +78,12 @@ Qed.
Lemma fin_to_nat_lt {n} (i : fin n) : fin_to_nat i < n.
Proof. induction i; simpl; lia. Qed.
Lemma fin_to_of_nat n m (H : n < m) : fin_to_nat (Fin.of_nat_lt H) = n.
Lemma fin_to_of_nat n m (H : n < m) : fin_to_nat (fin_of_nat H) = n.
revert m H. induction n; intros [|?]; simpl; auto; intros; exfalso; lia.
Lemma fin_of_to_nat {n} (i : fin n) H : @fin_of_nat (fin_to_nat i) n H = i.
Proof. apply (inj fin_to_nat), fin_to_of_nat. Qed.
Fixpoint fin_plus_inv {n1 n2} : (P : fin (n1 + n2) Type)
(H1 : i1 : fin n1, P (Fin.L n2 i1))
......@@ -258,16 +260,28 @@ Lemma vec_to_list_take_drop_lookup {A n} (v : vec A n) (i : fin n) :
vec_to_list v = take i v ++ v !!! i :: drop (S i) v.
Proof. rewrite <-(take_drop i v) at 1. by rewrite vec_to_list_drop_lookup. Qed.
Lemma vlookup_lookup {A n} (v : vec A n) (i : fin n) x :
v !!! i = x (v : list A) !! (i : nat) = Some x.
induction v as [|? ? v IH]; inv_fin i. simpl; split; congruence. done.
Lemma vlookup_lookup' {A n} (v : vec A n) (i : nat) x :
( H : i < n, v !!! (fin_of_nat H) = x) (v : list A) !! i = Some x.
- intros [Hlt ?]. rewrite <-(fin_to_of_nat i n Hlt). by apply vlookup_lookup.
- intros Hvix. assert (Hlt:=lookup_lt_Some _ _ _ Hvix).
rewrite vec_to_list_length in Hlt. exists Hlt.
apply vlookup_lookup. by rewrite fin_to_of_nat.
Lemma elem_of_vlookup {A n} (v : vec A n) x :
x vec_to_list v i, v !!! i = x.
- induction v; simpl; [by rewrite elem_of_nil |].
inversion 1; subst; [by eexists 0%fin|].
destruct IHv as [i ?]; trivial. by exists (FS i).
- intros [i ?]; subst. induction v as [|??? IH]; inv_fin i; [by left|].
right; apply IH.
rewrite elem_of_list_lookup. setoid_rewrite <-vlookup_lookup'.
split; [by intros (?&?&?); eauto|]. intros [i Hx].
exists i, (fin_to_nat_lt _). by rewrite fin_of_to_nat.
Lemma Forall_vlookup {A} (P : A Prop) {n} (v : vec A n) :
Forall P (vec_to_list v) i, P (v !!! i).
Proof. rewrite Forall_forall. setoid_rewrite elem_of_vlookup. naive_solver. Qed.
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