filterEntries :: (Entry -> Bool) -> Entries -> Entries
filterEntries p =
  foldrEntries
    (\entry rest -> if p entry
                      then Next entry rest
                      else rest)
    Done Fail
filterEntries :: (Entry -> Bool) -> Entries -> Entries
filterEntries p =
  foldrEntries
    (\entry rest -> if p entry
                      then Next entry rest
                      else rest)
    Done Fail
filterEntries p =
  foldrEntries
    (\entry rest -> if p entry
                      then Next entry rest
                      else rest)
    Done Fail