obsoleted "metisFT", and added "no_types" version of Metis as fallback to Sledgehammer after noticing how useful it can be
/* Title: Pure/General/exn.scala
Author: Makarius
Extra support for exceptions (arbitrary throwables).
*/
package isabelle
object Exn
{
/* runtime exceptions as values */
sealed abstract class Result[A]
case class Res[A](val result: A) extends Result[A]
case class Exn[A](val exn: Throwable) extends Result[A]
def capture[A](e: => A): Result[A] =
try { Res(e) }
catch { case exn: Throwable => Exn[A](exn) }
def release[A](result: Result[A]): A =
result match {
case Res(x) => x
case Exn(exn) => throw exn
}
}