src/Pure/ROOT.scala

   val proper_string = Library.proper_string _
   def proper_list[A](list: List[A]): Option[List[A]] = Library.proper_list(list)
   def if_proper[A](x: Iterable[A], body: => String): String = Library.if_proper(x, body)
   def if_proper(b: Boolean, body: => String): String = Library.if_proper(b, body)
 }
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