( ( even
  =
    . @( !arg
       :   ?
           [-2
           ( 0
           | 2
           | 4
           | 6
           | 8
           )
       )
  )
& (odd=.~(even$!arg))
& ( eventest
  =
    .   out
      $ (!arg is (even$!arg&|not) even)
  )
& ( oddtest
  =
    .   out
      $ (!arg is (odd$!arg&|not) odd)
  )
& eventest$5556
& oddtest$5556
& eventest$857234098750432987502398457089435
& oddtest$857234098750432987502398457089435
)