[Haskell-beginners] mind your head, was: Parsing a file with data divided into sections

[Christian Maeder]

Magnus Therning wrote:
>>         isSection line = not . isSpace . head $ line

I'ld be more careful with "head"! Imagine your binary fails with:

Prelude.head: empty list

> countDays [] = []
> countDays ls = let
>         day = head ls
>         count = length $ takeWhile (isSpace . head) $ tail ls
>     in (day, count) : countDays (drop (1 + count) ls)

here too, and better use a pattern like: ls@(hd, tl)

Cheers Christian