--1.- 
plural :: [String] -> [String]
plural xs = map (ponerEse) xs

ponerEse:: String -> String
ponerEse pal
 | elem (last pal) "aeiou" = pal ++ "s"
 | otherwise     = pal

-- Main> plural ["casa", "árbol", "barco", "tren"]
-- ["casas","\225rbol","barcos","tren"]  

--2.-
-- f :: a -> (b,a)
-- g :: b -> a -> c
-- h = (uncurry g).f

-- 
-- h x = ((uncurry g).f) x
-- h x = (uncurry g) (f x)  =>   x :: a  =>  (f x):: (b,a)
-- h x = (uncurry g) (f x) :: c
-- 
--  h :: a -> c 


--3.-
paresAdy [] = []
paresAdy [x] = []
paresAdy xs = zip xs (tail xs)

-- Otra solución 
paresAdy' xs
	| length xs < 1 = []
	| otherwise = zip xs (tail xs)

--4.-
--f = reverse . dropWhile (== 0) . reverse
f xs
 | last xs == 0 = (f.init) xs
 | otherwise    = xs


--5.-

data DigBin = Cero | Uno deriving (Eq, Show)

sumDig :: DigBin -> DigBin -> (DigBin,DigBin)
sumDig Cero Cero = (Cero,Cero) 
sumDig Uno Uno = (Cero,Uno)
sumDig _ _ = (Uno,Cero)

-- data DigBin = Cero | Uno deriving (Enum, Eq, Show)
-- Usando que fromEnum Cero = 0 y fromEnum Uno = 1 
-- sumDig :: DigBin -> DigBin -> (DigBin,DigBin)
-- sumDig x y =  (toEnum ((fromEnum x + fromEnum y) `div` 2), toEnum ((fromEnum x + fromEnum y) `mod` 2))

type NumBin = [DigBin]

sumNum :: NumBin -> NumBin -> NumBin
sumNum n1 n2 
	| dif == 0 = reverse (sumNumR Cero (reverse n1) (reverse n2))
	| dif < 0  = reverse (sumNumR Cero (compCeros (negate dif) (reverse n1)) (reverse n2))
	| otherwise = reverse (sumNumR Cero (reverse n1) (compCeros dif (reverse n2)))
	  where dif = length n1 - length n2 
		compCeros m xs = xs ++ [Cero | i<-[1..m]] 

sumNumR :: DigBin -> NumBin -> NumBin -> NumBin
sumNumR r [] [] = [r]
sumNumR r (x:xs) (y:ys) = d2 :(sumNumR r3 xs ys)
			  where (d1,r1) = sumDig x y
				(d2,r2) = sumDig d1 r
				(r3,r4) = sumDig r1 r2
-}
-- Main> sumNum [Uno,Uno,Cero,Uno] [Uno,Cero,Uno,Uno,Uno]
-- [Uno,Cero,Cero,Uno,Cero,Cero]  
-- Main> sumNum [Uno,Cero,Uno,Uno,Uno] [Uno,Uno,Cero,Uno]
-- [Uno,Cero,Cero,Uno,Cero,Cero]  
-- Main> sumNum [Uno,Cero,Uno,Uno,Uno] [Cero,Uno,Uno,Cero,Uno]
-- [Uno,Cero,Cero,Uno,Cero,Cero]     

--6.-
-- a) con listas intensionales
listaEjer2 = [(x,x+2) | x <-[1,5..]]
-- b) sin ellas
listaEjer2' = ps 
              where ps = (1,3): map  (\(x,y)->(x+4,y+4)) ps

-- Main> take 10 listaEjer2
-- [(1,3),(5,7),(9,11),(13,15),(17,19),(21,23),(25,27),(29,31),(33,35),(37,39)] 
-- Main> take 10 listaEjer2'
-- [(1,3),(5,7),(9,11),(13,15),(17,19),(21,23),(25,27),(29,31),(33,35),(37,39)]