src/HOL/Tools/ATP/atp_satallax.ML

       ((id, [id]), Axiom, AAtom (ATerm((id, []), [])), "", [])
     fun transform_one_step already_transformed (Satallax_Step {id, theorem, used_assumptions, role,
         rule, ...}) =
       let
         val role' = role_of_tptp_string role
-        val new_transformed = List.filter
+        val new_transformed = filter
           (fn s => size s >=4 andalso not (is_special_satallax_rule s) andalso not
           (member (op =) already_transformed s)) used_assumptions
       in
         (map create_fact_step new_transformed
         @ [((id, []), if role' = Unknown then Plain else role', theorem, rule,