Chapter 6 Exercises of Haskell Book

chapter-6.hs

import qualified Data.List (sort)

data Person = Person Bool
instance Show Person where
  show (Person b) = show b

printPerson :: Person -> IO ()
printPerson person = putStrLn (show person)

data Mood = Blah | Woot deriving (Show, Eq)
settleDown x = if x == Woot then Blah else x

type Subject = String
type Verb = String
type Object = String

data Sentence = Sentence Subject Verb Object deriving (Eq, Show)

s1 = Sentence "dogs" "drool" -- Will compile, but won't be shown since we haven't derived a way to Show Object->Sentence
s2 = Sentence "Julie" "loves" "dogs"

data Rocks = Rocks String deriving (Eq, Show)
data Yeah = Yeah Bool deriving (Eq, Show)
data Papu = Papu Rocks Yeah deriving (Eq, Show)

phew = Papu (Rocks "chases") (Yeah True)
truth = Papu (Rocks "chomskydoz") (Yeah True)

equalityForall :: Papu -> Papu -> Bool
equalityForall p p' = p == p'

-- comparePapus :: Papu -> Papu -> Bool
-- comparePapus p p' = p > p'

i :: Num a => a
i = 1

f :: RealFrac a => a
f = 1.0

freud :: Ord a => a -> a
freud x = x

freud' :: Int -> Int
freud' x = x

myX = 1 :: Int
sigmund :: Int -> Int
sigmund x = myX

sigmund' :: Int -> Int
sigmund' x = myX

jung :: [Int] -> Int
jung xs = head (Data.List.sort xs)

young :: Ord a => [a] -> a
young xs = head (Data.List.sort xs)

mySort :: [Char] -> [Char]
mySort = Data.List.sort

signifier :: [Char] -> Char
signifier xs = head (mySort xs)

chk :: Eq b => (a->b) -> a -> b -> Bool
chk f a b = f a == b

arith :: Num b => (a -> b) -> Integer -> a -> b
arith f i a = (+) (f a) (fromInteger i)