src/HOL/arith_data.ML

  [Simplifier.change_simpset_of (op addsimprocs) nat_cancel_sums] @
   init_lin_arith_data @
   [Simplifier.change_simpset_of (op addSolver)
    (mk_solver "lin. arith." Fast_Arith.cut_lin_arith_tac),
   Simplifier.change_simpset_of (op addsimprocs) [fast_nat_arith_simproc],
-  Method.add_methods [("arith", (arith_method o # 2) oo Method.syntax Args.bang_facts,
+  Method.add_methods [("arith", (arith_method o #2) oo Method.syntax Args.bang_facts,
     "decide linear arithmethic")],
   Attrib.add_attributes [("arith_split",
     (Attrib.no_args arith_split_add, Attrib.no_args Attrib.undef_local_attribute),
     "declaration of split rules for arithmetic procedure")]];