project_euler.hs

-- q1
sum [ n |  n <- [1..1000-1], n `mod` 3 == 0 ||  n `mod` 5 == 0 ]

-- q2
let fib = 1 : 1 : zipWith (+) fib (tail fib)
in sum (takeWhile (< 4000000) [ n | n <- fib, n `mod` 2 == 0 ])

-- q3 (not working)
let n = 600851475143
let factors n = [ (n `div` x) | x <- [2..(n `div` 2)], n `mod` (n `div` x) == 0 ]
let prime = null.nub.factors
take 1 [x | x <- (nub (factors n)), prime x ]