module Ejercicios where
import Data.Char

-- EJERCICIOS SOBRE TIPOS BASICOS

-- Ejercicio 1
siguienteLetra :: Char -> Char
siguienteLetra 'z' = 'a'
siguienteLetra 'Z' = 'A'
siguienteLetra a = chr ((ord a) + 1)

-- Ejercicio 2
sumatorio :: Int -> Int -> Int
sumatorio a b
    | a == b = a
    | otherwise = a + (sumatorio (a + 1) b)

-- Ejercicio 3
productorio :: Int -> Int -> Int
productorio a b
    | a == b = a
    | otherwise = a * (productorio (a + 1) b)

-- Ejercicio 4
maximo :: Int -> Int -> Int
maximo a b
    | signum (a - b) == 1 = a
    | otherwise = b

-- Ejercicio 5
fact :: Int -> Int
fact 0 = 1
fact n = n * fact (n - 1)

-- Ejercicio 6
sumaFacts :: Int -> Int
sumaFacts 0 = fact 0
sumaFacts n = fact n + sumaFacts (n - 1)

-- EJERCICIOS SOBRE TIPOS LISTAS

-- Ejercicio 1
sumaPares :: [(Int, Int)] -> [Int]
sumaPares [] = []
sumaPares (x:xs) = fst x + snd x : sumaPares xs
-- Alternativa sumaPares ((x, y):xs) = x+y : sumaPares xs

-- Ejercicio 2
cab :: [a] -> a
cab (x:xs) = x
cola :: [a] -> a
cola (x:xs)
    | xs == [] = x
    | otherwise = cola xs

-- Ejercicio 3
divisores :: Int -> [Int]
divisores n = [i | i <- [1..n], mod n i == 0]

-- Ejercicio 4
enLista :: Int -> [Int] -> Bool
enLista n [] = False
enLista n (x:xs)
    | n == x = True
    | otherwise = enLista n xs

-- Ejercicio 5
replace :: [Int] -> Int -> Int -> [Int]
replace [] n p = []
replace (x:xs) n p
    | x == n = p : replace xs n p
    | otherwise = x : replace xs n p

-- Ejercicio 6
count :: Int -> [Int] -> Int
count n [] = 0
count n (x:xs)
    | n == x = 1 + count n xs
    | otherwise = count n xs

-- Ejercicio 7
multiplosCinco :: [Int]
multiplosCinco = [x * 5 | x <- [1..]] -- Listas intensionales multiplicando
multiplosCinco4 :: [Int]
multiplosCinco4 = [x | x <- [1..], mod x 5 == 0] -- Listas intensionales comprobando
multiplosCinco2 :: [Int]
multiplosCinco2 = map (* 5) [1..] -- Orden superior (map)
multiplosCinco3 :: [Int]
multiplosCinco3 = filter (\x -> mod x 5 == 0) [1..] -- Orden superior (filter)

-- Ejercicio 8
cogeMayus :: [Char] -> [Char]
cogeMayus [] = []
cogeMayus (x:xs)
    | isUpper x = x : cogeMayus xs
    | otherwise = cogeMayus xs