shitennou.egi

(filter (match-lambda (list something)
          {[(& <snoc ,D _>
               <join _ <cons ,B <join _ <cons ,C _>>>>
               <snoc _ <snoc _ <nioj _ <snoc ,B _>>>>
               <join _ <cons ,C <join _ <cons ,A _>>>>)
            #t]
           [_ #f]})
	(match-all {A B C D} (multiset something)
          [<cons $a <cons $b <cons $c <cons $d <nil>>>>> {a b c d}]))