One Solution To Euler 12

Nothing special but play haskell for fun.

Priming is a simple module which can be found at ¹

  module Main where

  import Data.List
  import Primeing (primeFactors)

  main :: IO ()
  main = print $ p12 500

  p12 :: Int -> Int
  p12 n = head $ filter (factorLimit n) [ smartGaus x | x <- [1..]]

  smartGaus :: Int -> Int
  smartGaus n = (1+n)*n `div` 2

  {-- |
    Is factor count under the limit
  --}
  factorLimit :: Int -> Int -> Bool
  factorLimit l n
    | 2 * sqrtInt n < l    = False
    | otherwise            = length (factors  n) >= l


  factors :: Int -> [Int]
  factors n = concat [ [x, n `div` x] | x <- [1..sqrtInt n], n `mod` x == 0 ]

  sqrtInt :: Int -> Int
  sqrtInt = truncate . sqrt . fromIntegral

Footnotes:

Priming module