AulaP3 PLP

factors n = [i | i <-[1..n], n `mod` i ==0 ]

isPrime n = factors n == [1,n]
primes =[n| n<-[2,3..], isPrime n == True]

nPrimes n = take n primes

sum' [] =0
sum' (x:xs) = x + sum' xs

multiply  [] = 1
multiply (x:xs) = x * multiply xs

c 1 = 1
c n = 1+2* c (n-1)

listC = [c n | n<- [1..15]]

lisCN n =[c i | i <- [1..n]]

c1000 = takeWhile (<1000) [c n | n <- [1..]]

--Ex.4
firstFromList [] = error "Empty list :) Be carefull"
firstFromList (x:_) = x -- key not only characters, give the type of declaration ... not general~, for the Second from the list

secondFromList ::[a] -> a
secondFromList [] = error "Empty!!!!"
secondFromList [_] = error "Only one"
secondFromList (_:x:_) = x

lastFromList :: [a]-> a
lastFromList [] = error "Empty list!"
lastFromList [x] = x
lastFromList (x:xs) = lastFromList xs

{--
5 - Define a function

            mergeLists :: [[a]] -> [a]

which returns the combined list of lists of any elements.

For example:

mergeLists [[1,2,3],[4,8],[9]]

returns the list [1,2,3,4,8,9].

mergeLists :: [[a]] -> [a]
mergeLists x = concat x
above good!
megelist
 mergeLists xs ++ [] = xs
mergeList xs
--}