Daniel Carrera wrote:
I've been studying more Haskell and I've improved a lot. But I just hit a small problem. I want to print all the elements of a linst (putStr). I'd like to write something like this:
print_list [] = do putStr ""
This looks as if you're confused. The keyword "do" is completely redundant. "do" does not mean "please ignore all rules and allow side effects", it rather means "please build a new action by sequencing what follows". So "do" with only one action after it is useless (and a sign of confusion). Have you ever heard about the "command" and "composite" design patterns? Well, in Haskell, you get them for free with monads.
print_list (x:xs) = (do putStr x) && print_list xs
print_list (x:xs) = do putStr x ; print_list xs
print_list xs = do putStr(join xs) where join [] = "" join (x:xs) = (show x) ++ "\n" ++ join xs
But the thing is, I want to write a lazy version of this function.
What's not lazy about it? If you think, join has to "complete" "before" putStr can be called, simply forget it. Those words don't even make sense in a lazy functional setting. Udo. -- Lost: gray and white female cat. Answers to electric can opener.