src/HOL/Library/Tree.thy
changeset 62650 7e6bb43e7217
parent 62202 e5bc7cbb0bcc
child 63036 1ba3aacfa4d3
--- a/src/HOL/Library/Tree.thy	Fri Mar 18 08:32:37 2016 +0100
+++ b/src/HOL/Library/Tree.thy	Fri Mar 18 10:14:56 2016 +0100
@@ -24,6 +24,9 @@
   "size1 \<langle>l, x, r\<rangle> = size1 l + size1 r"
 by (simp_all add: size1_def)
 
+lemma size1_ge0[simp]: "0 < size1 t"
+by (simp add: size1_def)
+
 lemma size_0_iff_Leaf: "size t = 0 \<longleftrightarrow> t = Leaf"
 by(cases t) auto