# HG changeset patch
# User desharna
# Date 1741100875 -3600
# Node ID 96cca71aa2125bb823c1981af268b20ddf5b15e5
# Parent  d60c3f1ba86f64b83a238564b668847ea588548e
added lemma filter_mset_eq_mempty_iff (thanks to Manuel Eberl)

diff -r d60c3f1ba86f -r 96cca71aa212 NEWS
--- a/NEWS	Tue Mar 04 15:19:08 2025 +0100
+++ b/NEWS	Tue Mar 04 16:07:55 2025 +0100
@@ -18,6 +18,7 @@
   - Renamed lemmas. Minor INCOMPATIBILITY.
       filter_image_mset ~> filter_mset_image_mset
   - Added lemmas.
+      filter_mset_eq_mempty_iff
       filter_mset_mono_strong
       filter_mset_sum_list
       set_mset_sum_list[simp]
diff -r d60c3f1ba86f -r 96cca71aa212 src/HOL/Library/Multiset.thy
--- a/src/HOL/Library/Multiset.thy	Tue Mar 04 15:19:08 2025 +0100
+++ b/src/HOL/Library/Multiset.thy	Tue Mar 04 16:07:55 2025 +0100
@@ -1337,6 +1337,9 @@
   qed
 qed
 
+lemma filter_mset_eq_mempty_iff: "filter_mset P A = {#} \<longleftrightarrow> (\<forall>x. x \<in># A \<longrightarrow> \<not>P x)"
+  by (auto simp: multiset_eq_iff count_eq_zero_iff)
+
 lemma filter_filter_mset: "filter_mset P (filter_mset Q M) = {#x \<in># M. Q x \<and> P x#}"
   by (auto simp: multiset_eq_iff)