Haskell : Project Euler 1-9

0001.hs

module Main where
import Data.List.Ordered (union)

main :: IO ()
main = print . sum . takeWhile (1000 >) $ union [3,6..] [5,10..]

0002.hs

module Main where
import Data.Numbers.Fibonacci

main :: IO ()
main = print . sum . filter even . takeWhile (4000000 >) . map fib $ [1..]

0003.hs

module Main where
import Data.Numbers.Primes(primeFactors)

main :: IO ()
main = print . maximum . primeFactors $ 600851475143

0004.hs

module Main where
import Control.Applicative
import Data.Ord
import Data.List.Ordered (mergeAllBy)

isPalindrome :: Show a => a -> Bool
isPalindrome = (==) <*> reverse <$> show

main :: IO ()
main = print $ solve [(x *) <$> xs | x <- xs] where
    solve = head . filter isPalindrome . mergeAllBy (comparing negate)
    xs = [999,998..100] :: [Integer]

0005.hs

module Main where

main :: IO ()
main = print . foldl1 lcm $ [1..20]

0006.hs

module Main where
import Control.Applicative

main :: IO ()
main = print . f $ [1..100] where
    f = (-) <$> (^ 2) . sum <*> sum . map (^ 2)

0007.hs

module Main where
import Data.Numbers.Primes(primes)

main :: IO ()
main = print $ primes !! 10000

0008.hs

module Main where
import List
import Char

main :: IO ()
main = print . maximum . map (product . take 5) . tails $ data008

data008 :: [Int]
data008 = map digitToInt . foldl1 (++) $ [
    "73167176531330624919225119674426574742355349194934",
    "96983520312774506326239578318016984801869478851843",
    "85861560789112949495459501737958331952853208805511",
    "12540698747158523863050715693290963295227443043557",
    "66896648950445244523161731856403098711121722383113",
    "62229893423380308135336276614282806444486645238749",
    "30358907296290491560440772390713810515859307960866",
    "70172427121883998797908792274921901699720888093776",
    "65727333001053367881220235421809751254540594752243",
    "52584907711670556013604839586446706324415722155397",
    "53697817977846174064955149290862569321978468622482",
    "83972241375657056057490261407972968652414535100474",
    "82166370484403199890008895243450658541227588666881",
    "16427171479924442928230863465674813919123162824586",
    "17866458359124566529476545682848912883142607690042",
    "24219022671055626321111109370544217506941658960408",
    "07198403850962455444362981230987879927244284909188",
    "84580156166097919133875499200524063689912560717606",
    "05886116467109405077541002256983155200055935729725",
    "71636269561882670428252483600823257530420752963450"]

0009.hs

module Main where
main :: IO ()
main = print . head $ [a*b*c
    | a <- [1..div 1000 3]
    , b <- [a..div (1000-a) 2]
    , c <- [1000-a-b]
    , a^2 + b^2 == c^2
    ]