[Haskell-cafe] >>= definition for list monad in ghc

[Michael Vanier]

Usually in monad tutorials, the >>= operator for the list monad is 
defined as:

m >>= k = concat (map k m)  -- or concatMap k m

but in the GHC sources it's defined as:

m  >>=  k  =  foldr  ((++)  .  k)  []  m

As far as I can tell, this definition is equivalent to the previous one (correct me if I'm wrong), so I was wondering why this definition was chosen instead of the other one.  Does anybody know?

Thanks in advance,

Mike