タプル化の簡単な例

TuplingExample.hs

module TuplingExample where

import Prelude hiding (even, odd)

even :: Int -> Bool
even n = if n==0 then True else odd (n-1)

odd :: Int -> Bool
odd n = if n==0 then False else even (n-1)

-- タプル化したもの
even_and_odd :: Int -> (Bool, Bool)
even_and_odd n =
  if n==0
  then (True, False)
  else
    case even_and_odd (n-1) of
      (e, o) -> (o, e)