(defined problem_generator() ? (generator => problem_generator) : ()),
(defined problem_runner() ? (runner => problem_runner) : ()),
(defined problem_judge() ? (judge => problem_judge) : ()),
(defined problem_generator() ? (generator => problem_generator) : ()),
(defined problem_runner() ? (runner => problem_runner) : ()),
(defined problem_judge() ? (judge => problem_judge) : ()),