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

I wrote:

Magnus Therning wrote:

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isSection line = not . isSpace . head $ line

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

Prelude.head: empty list

see also http://haskell.org/haskellwiki/Haskell_programming_tips#Partial_functions_li...

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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)

oops, the pattern should be: ls@(hd : tl) Cheers again Christian