checkEntries :: (Entry -> Maybe String) -> Entries -> Entries
checkEntries checkEntry =
  foldrEntries
    (\entry rest -> case checkEntry entry of
                      Nothing  -> Next entry rest
                      Just err -> Fail err)
    Done Fail
checkEntries :: (Entry -> Maybe String) -> Entries -> Entries
checkEntries checkEntry =
  foldrEntries
    (\entry rest -> case checkEntry entry of
                      Nothing  -> Next entry rest
                      Just err -> Fail err)
    Done Fail
checkEntries checkEntry =
  foldrEntries
    (\entry rest -> case checkEntry entry of
                      Nothing  -> Next entry rest
                      Just err -> Fail err)
    Done Fail