module ReaderPractice where

import Control.Applicative
import Data.Maybe

x :: [Integer]
x = [1, 2, 3]
y :: [Integer]
y = [4, 5, 6]
z :: [Integer]
z = [7, 8, 9]

xs :: Maybe Integer
xs = lookup 3 $ zip x y

ys :: Maybe Integer
ys = lookup 6 $ zip y z

zs :: Maybe Integer
zs = lookup 4 $ zip x y

z' :: Integer -> Maybe Integer
z' n = lookup n $ zip x z

x1 :: Maybe (Integer, Integer)
x1 = liftA2 (,) xs ys

x2 :: Maybe (Integer, Integer)
x2 = liftA2 (,) ys zs

x3 :: Integer -> (Maybe Integer, Maybe Integer)
x3 = liftA2 (,) z' z'

summed :: Num c => (c, c) -> c
summed = uncurry (+)

bolt :: Integer -> Bool
bolt = liftA2 (&&) (>3) (<8)

sequA :: Integral a => a -> [Bool]
sequA m = sequenceA [(>3), (<8), even] m

s' :: Maybe Integer
s' = summed <$> ((,) <$> xs <*> ys)

main :: IO ()
main = do
    -- print $ sequenceA [Just (3 :: Integer), Just 2, Just 1]
    -- print $ sequenceA [x, y]
    -- print $ sequenceA [xs, ys]
    -- print $ summed <$> ((,) <$> xs <*> ys)
    -- print $ fmap summed ((,) <$> xs <*> zs)
    -- print $ bolt 7
    -- print $ fmap bolt z
    print $ and $ sequA (7 :: Integer)
    print $ sequA $ fromMaybe 0 s'
    print $ bolt $ fromMaybe 0 ys