|multSM d m = [[(b*a)| b<-[d], a<-(head m)]]
Well, let's see what do we have here. We have []'s around something. "Something" is [(b*a)| b<-[d], a<-(head m)], which is just a legal Haskell value, so our "mutlSM d m" has to be a one-element list, with the only element being equal to what we put inside the brackets. It's like [1] or ["Hello"], just with more complex expression inside. This unique value is, as we've seen, [(b*a)| b<-[d], a<-(head m)]. Here we also have []'s around something, but this new "something" is NOT a legal Haskell value; it's a list comprehension. That means that we have something like this: multSM d m = [concatMap (\b -> concatMap (\a -> b*a) (head m)) [d]] Now, concatMap f [d] = f d, so multSM d m = [concatMap (\a -> d*a) (head m)] and if m = [m1:ms], then multSM d m = [concatMap (\a -> d*a) m1] So, you take first row ("head" only takes the first element of the list, you know), multiply it by "d", and make a one-element list of it.