----------------------------- 1.9 ---------------------------------

f2p :: (a -> (b,c)) -> (a -> b, a -> c)
f2p f  = (fst . f, snd . f)

testF :: Double -> (Integer, String)
testF d = (round d, show d)

p2f :: (a -> b, a -> c) -> (a -> (b,c))
p2f (f,g) = (\x -> (f x, g x))


---------------------------- 1.10 --------------------------------

s2p :: (Either b c -> a) -> (b -> a, c -> a)
s2p f = (f . Left, f . Right)


p2s :: (b -> a, c -> a) -> (Either b c -> a)
p2s (f,g) = (\x -> either f g x)

--------------------------- 1.11 ---------------------------------

-- a : Card A
-- b : Card B
-- c : Card C


-- Either a b   : A + B
-- (a,b)        : A * B
-- a -> b       :

--------------------------- 1.12 ---------------------------------

isoR :: (Bool -> t) -> (t,t)
isoR f = (f False, f True)

isoL :: (t,t) -> (Bool -> t)
isoL (x,y) = (\b -> if b then y else x)

--------------------------- 1.13 --------------------------------