[codygman]

example:

    nWords = liftM (train . lowerWords . B.unpack) (B.readFile "big.txt")

There was recently a very good article[0] about practically using monads that mentioned using liftM.

However whenever using a functor instance is possible it's probably better, since functors can't do as much as monads. I'm not quite sure how much this would help/apply to this small example though.

0: http://softwaresimply.blogspot.com/2014/12/ltmt-part-3-monad...