Commit 24c28e2c authored by Robbert Krebbers's avatar Robbert Krebbers

Relate subseteq on collections to the extension order.

parent a0348d7c
......@@ -645,6 +645,11 @@ Section collection.
intros ? x; split; rewrite !elem_of_union, elem_of_difference; [|intuition].
destruct (decide (x X)); intuition.
Qed.
Lemma subseteq_disjoint_union X Y : X Y Z, Y X Z X Z.
Proof.
split; [|set_solver].
exists (Y X); split; [auto using union_difference|set_solver].
Qed.
Lemma non_empty_difference X Y : X Y Y X .
Proof. intros [HXY1 HXY2] Hdiff. destruct HXY2. set_solver. Qed.
Lemma empty_difference_subseteq X Y : X Y X Y.
......@@ -657,6 +662,8 @@ Section collection.
Proof. unfold_leibniz. apply non_empty_difference. Qed.
Lemma empty_difference_subseteq_L X Y : X Y = X Y.
Proof. unfold_leibniz. apply empty_difference_subseteq. Qed.
Lemma subseteq_disjoint_union_L X Y : X Y Z, Y = X Z X Z.
Proof. unfold_leibniz. apply subseteq_disjoint_union. Qed.
End dec.
End collection.
......
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