object Gavno -implemented:using Mocha {}

extend box< Collection {
 fn |T: iso Any, E: iso Exception| map
 (using: fn (box< Self.Element) -throws: E -returns: T)
 -throws: some iso Exception
 -returns: some iso |Element: iso T| Collection {
  var `result collection`: box = !recover: {
   return |T|Collection.`create default empty collection`(`with initial capacity`: self.count);
  };
  self.forEach(do: fn {
   `result collection`.append(transformer($0));
  });
  return `result collection`;
 };
 fn |T: iso Any, E: iso Exception| `safely map`
 (using transformer: fn (Self.ELement) -sealed -throws: E -returns: T)
 -throws: some iso Exception
 -returns: some val |Element: box T| Collection {
  var `result collection`: box = !recover: {
   return |T|Collection.`create default empty collection`(`with initial capacity`: self.count);
  };
  self.forEach(do: fn {
   `result collection`.append(transformer($0));
  });
  return `result collection`;
 };
};