orclev

import Data.Maybe
import Control.Monad (liftM)
import Data.List (isPrefixOf)
import qualified Data.Map as M
import qualified Data.Foldable as F

-- | Trie container data type
data Trie a = Trie { value    :: Maybe a
                   , children :: M.Map Char (Trie a) }
              deriving (Show)

orclev

import Data.List

collatz :: Int -> Int
collatz 1 = 0
collatz n
  | odd n  = force $ (collatz $! 3*n+1) + 1
  | even n = force $ (collatz $! div n 2) + 1

force x = x `seq` x