tst30000 =
    runST $
    do
    t <- list_dubst [1..30000]
    dubst_size t
tst30000 =
    runST $
    do
    t <- list_dubst [1..30000]
    dubst_size t
tst30000 =
    runST $
    do
    t <- list_dubst [1..30000]
    dubst_size t