ch2.hs

square x = x * x

double x = x + x

factorial n = if n == 1
              then 1
              else n * factorial (n - 1)

evaluate f x = f x

sumList l = if null l 
            then 0
            else (head l) + sumList (tail l)

lengthL l = if null l 
           then 0
           else 1 + lengthL (tail l) 

multiplyL l = if null l 
            then 1
            else (head l) * multiplyL (tail l)

increaseL l n = if null l
                then l
                else (head l) * n : increaseL (tail l) n

[x*2 | x <- [1..10]]

take 10 [x | x <- [1..], even x]
take 10 [x | x <- [1..], odd x]

boomBangs xs = [ if x < 10 then "BOOM!" else "BANG!" | x <- xs, odd x]
boomBangs [7..13]
[ x | x <- [10..20], x /= 13, x /= 15, x /= 19] 

combineLists xs ys = [x*y | x <- xs, y <- ys]

let nouns = ["hobo", "from", "pope"]
let adjectives = ["lazy", "grouchy", "scheming"]
[noun ++ " " ++ adjective | noun <- nouns , adjective <- adjectives]

length' xs = sum [1 | _ <- xs]
onlyEvens xs = [x | x <- xs, even x]

removeNonUppercase st = [ c | c <- st, c `elem` ['A'..'Z']]   

let xxs = [[1,3,5,2,3,1,2,4,5],[1,2,3,4,5,6,7,8,9],[1,2,4,2,1,6,3,1,3,2,3,6]]  
[ [ x | x <- xs, even x ] | xs <- xxs]  

-- Tuples
zip [1,2,3,4,5] [5,5,5,5,5]  

factorial n = product [1..n]