M: merged length
seqs>> [ [ length ] [ min ] map-reduce ] [ length ] bi * ; inline
-M: merged virtual@ ( n seq -- n' seq' )
+M: merged virtual@
seqs>> [ length /mod ] [ nth-unsafe ] bi ; inline
-M: merged virtual-exemplar ( merged -- seq )
+M: merged virtual-exemplar
seqs>> ?first ; inline
INSTANCE: merged virtual-sequence