import Char  -- for intToDigit

gen :: Int -> Int -> [String]
gen 0 _ = []
gen len max = do
  d  <- map intToDigit [0 .. max-1]
  ds <- [] : gen (len-1) max
  return (d:ds)

##</code><code>##

gen :: Int -> Int -> [String]
gen 0 _ = []
gen len max =
  concat (
    map (
          \digit -> [digit] : (
                                map ( digit : )
                                    ( gen (len - 1) max )
                              )
        )
        ( map intToDigit [0 .. max-1] )
  )