-- Collected Haskell code of Section 11.6 from
-- Kenneth C. Louden, Programming Languages
-- Principles and Practice 2nd Edition
-- Copyright (C) Brooks-Cole/ITP, 2003

-- page 513

fact 0 = 1
fact n = n * fact (n - 1)
square x = x * x
gcd1 u v = if v == 0 then u else gcd1 v (mod u v)
reverse1 [] = []
reverse1 (h:t) = reverse1 t ++ [h]

plus2 = (2 +)

times3 = (* 3)

-- page 514

square_list = map (\ x -> x * x)

type ListFn a = [a] -> [a]
type Salary = Float
type Pair a b = (a,b)
data BST a = Nil | Node a (BST a) (BST a) 

flatten:: BST a -> [a]
flatten Nil = []
flatten (Node val left right) = 
          (flatten left) ++ [val] ++ (flatten right)

-- page 515

square_list2 lis = [ x * x | x <- lis]

square_list_positive lis = [ x * x | x <- lis, x > 0]

qsort [] = []
qsort (h:t) = qsort [x | x <- t, x <= h] ++
                    [h] ++ qsort [x | x <- t, x > h]

f x = 2

my_if x y z = if x then y else z

ones = 1 : ones

-- page 516

sieve (p : lis) = p : sieve [n | n <- lis , mod n p /= 0]
primes = sieve [2..]

-- pages 519-520 (modified to avoid clash with previous definition)

data BST2 a = Nil2 | Node2 a (BST2 a) (BST2 a) 
              deriving (Show,Eq)

tree = Node2 "horse" 
            (Node2 "cow" Nil2 (Node2 "dog" Nil2 Nil2))
            (Node2 "zebra" (Node2 "yak" Nil2 Nil2) Nil2)