Day3

sumL :: [Int] -> Int
sumL [] = 0
sumL (x:xs) = x + sumL xs

po10 :: Int -> Int
po10 x = 10 * x

mapMy :: (Int->Int) -> [Int] -> [Int]
mapMy f [] = []
mapMy f (x:xs) = (f x) : mapMy f xs

isLast0 :: Int -> Bool
isLast0 x
    | mod x 10 == 0 = True
    | otherwise     = False

filterMy :: (Int->Bool) -> [Int] -> [Int]
filterMy p [] = []
filterMy p (x:xs)
    | p x == True = x : filterMy p xs
    | otherwise   = filterMy p xs

filterMy2 :: (Int->Bool) -> [Int] -> [Int]
filterMy2 p list = [n | n <- list, p n]

reverseMy :: [a] -> [a]
reverseMy [] = []
reverseMy (x:xs) = reverseMy xs ++ [x]

insert :: Int -> [Int] -> [Int]
insert x [] = [x]
insert x (y:ys)
    | x <= y    = x:(y:ys)
    | otherwise = y : insert x ys

insertSort :: [Int] -> [Int]
insertSort [] = []
insertSort (x:xs) = insert x (insertSort xs)

qSort :: [Int] -> [Int]
qSort [] = []
qSort (x:xs) = qSort (filter (<x) xs) ++ [x] ++ qSort (filter (>=x) xs)

repeated :: (a->a) -> Int -> (a->a)
repeated f 1 = f
repeated f n = \x -> f (repeated f (n - 1) x)

derive :: (Float->Float) -> (Float->Float)
derive f = \x -> (f (x + dx) - f x) / dx
    where dx = 0.01