eval (QEmptiest tq) c wo =
  -- TODO is the built-in sortBy stable?
  map snd
  $ sortBy (\a b -> compare (fst a) (fst b))
  $ map (\(tr, h) -> (size $ wTiles wo ! tr, (tr, h)))
  $ eval tq c wo
eval (QEmptiest tq) c wo =
  -- TODO is the built-in sortBy stable?
  map snd
  $ sortBy (\a b -> compare (fst a) (fst b))
  $ map (\(tr, h) -> (size $ wTiles wo ! tr, (tr, h)))
  $ eval tq c wo
eval (QEmptiest tq) c wo =
  -- TODO is the built-in sortBy stable?
  map snd
  $ sortBy (\a b -> compare (fst a) (fst b))
  $ map (\(tr, h) -> (size $ wTiles wo ! tr, (tr, h)))
  $ eval tq c wo