#!/usr/bin/runghc

module Recursion04EvenOdd where

import Data.Bits

isEven :: Int -> Bool
isEven 0 = True
isEven n = isOdd (n - 1)

isOdd :: Int -> Bool
isOdd 0 = False
isOdd n = isEven (n - 1)

main :: IO ()
main = do
  putStrLn "Slowest:"
  print (isEven 10)
  print (isEven 5)
  print (isOdd 10)
  print (isOdd 5)

  putStrLn "\nLess slow:"
  print (mod 10 2 == 0)
  print (mod 5 2 == 0)
  print (mod 10 2 /= 0)
  print (mod 5 2 /= 0)

  putStrLn "\nFastest:"
  print ((10 :: Int) .&. 1 == 0)
  print ((5 :: Int) .&. 1 == 0)
  print ((10 :: Int) .&. 1 /= 0)
  print ((5 :: Int) .&. 1 /= 0)

  putStrLn "\nBuilt in:"
  print (even 10)
  print (even 5)
  print (odd 10)
  print (odd 5)