From 0a5ee4f43e91fe8e36586a3fddd0279402c7d430 Mon Sep 17 00:00:00 2001
From: Robbert Krebbers <mail@robbertkrebbers.nl>
Date: Sat, 23 Jul 2016 01:22:12 +0200
Subject: [PATCH] Version of fresh using an existential.

---
 theories/collections.v | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/theories/collections.v b/theories/collections.v
index 88daad82..db4d470e 100644
--- a/theories/collections.v
+++ b/theories/collections.v
@@ -807,6 +807,8 @@ Section fresh.
     apply IH. by rewrite E.
   Qed.
 
+  Lemma exist_fresh X : ∃ x, x ∉ X.
+  Proof. exists (fresh X). apply is_fresh. Qed.
   Lemma Forall_fresh_NoDup X xs : Forall_fresh X xs → NoDup xs.
   Proof. induction 1; by constructor. Qed.
   Lemma Forall_fresh_elem_of X xs x : Forall_fresh X xs → x ∈ xs → x ∉ X.
-- 
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