-- 1) 

data Temp = C Float | F Float

deCaF x = 9/5 * x + 32

instance Eq Temp where
	C x == C y = x == y
	F x == F y = x == y
	C x == F y = deCaF x == y
	F x == C y = C y == F x

instance Show Temp where
	show (C x) = (show x)++"ºC"
	show (F x) = (show x)++"ºF"

--2)

union p lis1 lis2 = [(x,y,u,v) | (x,y) <-lis1, (u,v)<-lis2, p x u]

--3)

sumaAlt lis = foldr (+) 0  (zipWith (*) lis aux)
              where aux = 1: aux'
                    aux'= (-1):aux


-- 4) 

f :: Int -> [a] -> [[a]]
f n = takeWhile (not . null) . map (take n) . iterate (drop n)

-- Main> f 3 ”apabepacepa!”
-- [”apa”,”bep”,”ace”,”pa!”]
-- Main> f 2 [1,2,3,4,5]
-- [[1,2],[3,4],[5]] 


-- 5)

zs = [(1,1)]:(map f1 zs) 
     where  f1 ((x,y):[]) = [(x+1,y),(x,y+1)]
            f1 ((x,y):ps) = (x+1,y): f1 ps

-- Los sucesivos elementos son:
-- [(1, 1)]
-- [(2, 1), (1, 2)]
-- [(3, 1), (2, 2), (1, 3)]
-- [(4, 1), (3, 2), (2, 3), (1, 4)] . . .