Nice program, especially your use of function composition is good style.
Thanks, I must admit I put alot of time into refactoring it. There's so many different ways of doing stuff (and then simplifying them) in Haskell!
I think that you've pretty much used accumulators in the way they most often are used. In many cases you don't _have_ to keep count though. Here's one way to get the same result, but without keeping count:
countDays [] = [] countDays ls = let day = head ls count = length $ takeWhile (isSpace . head) $ tail ls in (day, count) : countDays (drop (1 + count) ls)
main = interact (unlines . map show . countDays . lines)
Here's a version using span from the Prelude:
main = interact $ unlines . map show . countDays . lines
countDays [] = [] countDays (day:xs) = (day, length people) : countDays xs' where (people, xs') = span (isSpace . head) xs
Both of these examples are great and exactly what I was looking for: a different approach to the problem. I guess the step that was missing in my "thought process" is that recursion doesn't have to imply processing the list elements 1 by 1 (1 recursive call for each element). Of course it makes perfect sense once you see it.... Thanks a lot to everyone, as usual the people on this list are always very kind and helpful. Patrick
Note that this file format is very simple and it's ok to use lines and isSpace to parse it. But the tool of choice are parser combinators like Text.Parsec or Text.ParserCombinators.ReadP .
-- http://apfelmus.nfshost.com
_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners
-- ===================== Patrick LeBoutillier Rosemère, Québec, Canada