Project euler problem 3 in haskell
- by shk
I'm new in Haskell and try to solve 3 problem from http://projecteuler.net/.
The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?
My solution:
import Data.List
getD :: Int -> Int
getD x =
-- find deviders
let deriveList = filter (\y -> (x `mod` y) == 0) [1 .. x]
filteredList = filter isSimpleNumber deriveList
in maximum filteredList
-- Check is nmber simple
isSimpleNumber :: Int -> Bool
isSimpleNumber x = let deriveList = map (\y -> (x `mod` y)) [1 .. x]
filterLength = length ( filter (\z -> z == 0) deriveList)
in
case filterLength of
2 -> True
_ -> False
I try to run for example:
getD 13195
> 29
But when i try:
getD 600851475143
I get error Exception: Prelude.maximum: empty list Why?
Thank you @Barry Brown, I think i must use:
getD :: Integer -> Integer
But i get error:
Couldn't match expected type `Int' with actual type `Integer'
Expected type: [Int]
Actual type: [Integer]
In the second argument of `filter', namely `deriveList'
In the expression: filter isSimpleNumber deriveList
Thank you.
