Jeff, Thank you for your reply.
>> After fn is lifted, where is "bind" used in allCombinations? >The bind happens inside the liftM2 function, which can be defined as >(taken from http://www.haskell.org/onlinereport/monad.html): >liftM2 f = \a b -> do { a' <- a; b' <- b; return (f a' b') } Using the above, I think that allCombinations can be rewritten: allCombinations fn (l:ls) = foldl (\a b -> do { a' <- a; b' <- b; return (fn a' b') }) l ls I'm not sure how "allCombinations (+) [[1,2][2,3]]" gets to the final result, since the above would seem to yield: allCombinations (+) [1,2]:[[2,3]] = foldl (\a b -> do { a' <- a; b' <- b; return (fn a' b') }) [1,2] [[2,3]] allCombinations (+) [1,2]:[[2,3]] = return ((+) [1,2] [2,3]) You mentioned on your site that the operation of the List monad is key to comprehending this function, but I still wasn't able to grok it. Any pointers would be appreciated. - Alson _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
