src/HOL/Quickcheck_Examples/Quickcheck_Narrowing_Examples.thy

   "is_ord (MKT n l r h) = ((\<forall>n' \<in> set (set_of' l). n' < n) \<and> (\<forall>n' \<in> set (set_of' r). n < n') \<and> is_ord l \<and> is_ord r)"
 by (simp add: set_of')
 
 declare is_ord.simps(1)[code] is_ord_mkt[code]
 
-subsubsection \<open>Invalid Lemma due to typo in @{const l_bal}\<close>
+subsubsection \<open>Invalid Lemma due to typo in \<^const>\<open>l_bal\<close>\<close>
 
 lemma is_ord_l_bal:
  "\<lbrakk> is_ord(MKT (x :: nat) l r h); height l = height r + 2 \<rbrakk> \<Longrightarrow> is_ord(l_bal(x,l,r))"
 quickcheck[tester = narrowing, finite_types = false, default_type = nat, size = 6, expect = counterexample]
 oops