embedly challenge

embedly

import Data.List

fact :: Integer -> Integer
fact x = foldl' (*) 1 [1..x]

sumdigits :: Integer -> Integer
sumdigits x
    | x < 10    = x
    | otherwise = let (a,b) = x `divMod` 10 in b + sumdigits a

-- convert text to list of number of spaces indented
indentsizes :: [String] -> [Int]
indentsizes [] = []
indentsizes (x:xs) = (length $ takeWhile (==' ') x) : (indentsizes xs)
-- convert list of numbers to increasing or decreasing depth measures
depth :: [Int] -> (Int,Int) -> [Int]
depth [] _ = []
depth (x:xs) (previndent,prevdepth) = thisdepth : (depth xs (x,thisdepth))
    where
        thisdepth = case compare x previndent of
            LT -> pred prevdepth
            EQ -> prevdepth
            GT -> succ prevdepth

ptags :: [String] -> [Bool]
ptags [] = []
ptags (x:xs) = (isPrefixOf "<p>" (dropWhile (==' ') x)) : (ptags xs)