src/HOL/Analysis/Binary_Product_Measure.thy

   "f \<in> measurable M (M1 \<Otimes>\<^sub>M M2) \<longleftrightarrow> (fst \<circ> f) \<in> measurable M M1 \<and> (snd \<circ> f) \<in> measurable M M2"
   by (auto intro: measurable_pair[of f M M1 M2])
 
 lemma measurable_split_conv:
   "(\<lambda>(x, y). f x y) \<in> measurable A B \<longleftrightarrow> (\<lambda>x. f (fst x) (snd x)) \<in> measurable A B"
-  by (intro arg_cong2[where f="op \<in>"]) auto
+  by (intro arg_cong2[where f="(\<in>)"]) auto
 
 lemma measurable_pair_swap': "(\<lambda>(x,y). (y, x)) \<in> measurable (M1 \<Otimes>\<^sub>M M2) (M2 \<Otimes>\<^sub>M M1)"
   by (auto intro!: measurable_Pair simp: measurable_split_conv)
 
 lemma measurable_pair_swap: