Rob Hoelz wrote:
item <- linked_list_getdata listPtr next <- linked_list_next listPtr cStr <- peek item hStr <- peekCString cStr t <- linkedListToStringList next return (hStr : t)
item <- linked_list_getdata listPtr next <- linked_list_next listPtr cStr <- peek item hStr <- peekCString cStr fmap (hStr :) linkedListToStringList next
This is just ugly...making the recursive call first, THEN consing the value on? However, this is the only way I could think of doing it. I figure there are three possibilities from here:
I think you're over-valuing tail recursion. It's not an exciting thing in a lazy language the way it is in a pure language. The change I made above may not result in particularly better code, although it is more concise.
And as long as I'm asking, is there some kind of monadic function composition operator? I'd like to clean up the above with something like peekCString . peek . linked_list_getdata...
Yes, that's what >>= and =<< are. hStr <- peekCString =<< peek =<< linked_list_getdata listPtr fmap (hStr :) linkedListToStringList =<< linked_list_next listPtr ...or even... liftM2 (:) (peekCString =<< peek =<< linked_list_getdata listPtr) (linkedListToStringList =<< linked_list_next listPtr) It's really a matter of taste.... you could turn the arrows round, too. Jules