gistfile1.hs

-- problem 1
myLast :: [a] -> a
myLast (x:[]) = x
myLast (x:xs) = myLast xs
myLast [] = error "Empty list"

myOneLineLast :: [a] -> a
myOneLineLast x = x !! (length x - 1)

-- problem 2
myButLast :: [a] -> a
myButLast (x:[]) = error "One element list"
myButLast (x:xs) = if length xs == 1 then x else myButLast xs
myButLast [] = error "Empty list"

myOneLineButLast :: [a] -> a
myOneLineButLast x = x !! (length x - 2)


-- problem 3
elementAt :: [a] -> Int -> a
elementAt (x:xs) 1 = x
elementAt (x:xs) v = elementAt xs (v-1)
elementAt _ _ = error "Index out of bounds"

myOneLineElementAt :: [a] -> Int -> a
myOneLineElementAt l v = l !! (v-1)


-- problem 4
myLength :: [a] -> Int
myLength l = foldl (\x o-> x+1) 0 l

myLength' :: [a] -> Int
myLength' = sum . map (\_ -> 1)  

-- problem 5
myReverse :: [a] -> [a]
myReverse l = foldl (\acc x  -> x:acc) [] l

myReverse' :: [a] -> [a]
myReverse' l = foldr (\x acc  -> acc ++ [x]) l []

gistfile2.hs

-- problem 6
isPalindrome :: Eq a => [a] -> Bool
isPalindrome l = (reverse l) == l

isPalindrome' :: Eq a => [a] -> Bool
isPalindrome' [] = True
isPalindrome' (x:[]) = True
isPalindrome' l = (head l == last l) && isPalindrome (init $ tail l)