50 Haskell Function

module Main where

-- Exercicio 1
enumFromTo' :: Int -> Int -> [Int]
enumFromTo' m n = if m > n then [] else m : enumFromTo' (m+1) n

enumFromTo'' :: Int -> Int -> [Int]
enumFromTo'' m n
    | m > n = []
    | otherwise = m : enumFromTo'' (m+1) n

-- Exercicio 2
enumFromThenTo' :: Int -> Int -> Int -> [Int]
enumFromThenTo' x y z
    | x > z = []
    | otherwise = x : enumFromThenTo' y (y + (y-x)) z

-- Exercicio 3
-- contact
concatLista :: [a] -> [a] -> [a]
concatLista [] ys = ys
concatLista (xs:xss) l = xs : concatLista xss l

-- Exercicio 4
last' :: [a] -> a
last' [] = error "Lista vazia"
last' [x] = x
last' (x:xs) = last' xs


-- Exercicio 5
init' :: [a] -> [a]
init' [a] = []
init' (xs:xss) = xs : init' xss

-- Exercicio 6
-- Devolve elemento x de uma lista
devolveElemento :: [a] -> Int -> a
devolveElemento (x:xs) i
    | i == 0 = x
    | otherwise = devolveElemento (xs) (i-1)

-- Exercicio 7
-- inverter a ordem de uma lista
inverte :: [a] -> [a]
inverte [] = []
inverte (x:xs) = (inverte xs) ++ [x]

-- Exercicio 8
-- Obtem uma lista com o x primeiros elementos
take' :: Int -> [a] -> [a]
take' _ [] = []
take' i (x:xs)
    | i == 0 = xs
    | otherwise = x : take' (i-1) xs

-- Exercicio 9
-- drop
drop' :: Int -> [a] -> [a]
drop' _ [] = []
drop' n (x:xs)
    | n <= 0 = x:xs
    | otherwise = drop' (n-1) xs

-- Exercicio 10
-- constroi uma lista de pares a partir de duas listas
zip' :: [a] -> [b] -> [(a, b)]
zip' [] _ = []
zip' _ [] = []
zip' (x:xs) (y:ys) = (x,y): zip' xs ys

-- Exercicio 11
-- Testa se um elemento esta na lista
-- definicao recursiva de elem
elem' :: Eq a => a -> [a] -> Bool
elem' n [] = False
elem' n (x:xs)
    | n == x = True
    | otherwise = elem' n xs

-- Exercicio 12
-- Dado um elemento n e um inteiro x constroi constriu uma lista com n
-- elementos todos iguais a x
-- definicao recursiva de replicate
replicate' :: Int -> a -> [a]
replicate' n x
    | n == 0 = []
    | otherwise = x : replicate' (n-1) x

-- Exercicio 13
-- intersperse
intersperse' :: a -> [a] -> [a]
intersperse' n [x] = [x]
intersperse' n (x:xs) = x:n:(intersperse' n xs)

-- Exercicio 14
group' :: Eq a => [a] -> [[a]]
group' [] = []
group' (x:xs) = (takeWhile (==x) xs) : group' (dropWhile (==x) xs)

group'' :: Eq a => [a] -> [[a]]
group'' [] = []
group'' (x:xs) = prefix : group'' suffix
    where
        head' = x
        prefix = [ n | n <- (x:xs), n == head' ]
        suffix = [ n | n <- (x:xs), n /= head' ]

-- Exercicio 15
-- contact
concat' :: [[a]] -> [a]
concat' [] = []
concat' (x:xs) = x ++ (concat' xs)

-- Exercicio 16
-- inits
inits' :: [a] -> [[a]]
inits' [] = [[]]
inits' (xs:xss) = inits' (init (xs:xss)) ++ [ xs:xss ]

-- Exercicio 17
-- tails
tails' :: [a] -> [[a]]
tails' [] = [[]]
tails' (xs:xss) = [(xs:xss)] ++ tails' (tail (xs:xss))