Programming Language Design Assignment #4

陳錕詮 107502570

Implement your own tail function

myTail' :: [a] -> [a]
myTail' [] = error "empty list"
myTail' [x] = []
myTail' (_:xs) = xs ++ myTail' xs

Implement your own last function

myLast' :: [a] -> a
myLast' [] = error "empty list"
myLast' [x] = x
myLast' (x:xs) = myLast' xs

Implement your own reverse function

myReverse' :: [a] -> [a]
myReverse' [] = []
myReverse' (x:[]) = [x]
myReverse' (x:xs) = myReverse' xs ++ [x]

Implement isPalindrome which checks a list is palindrome or not

isPalindrome :: Eq a => [a] -> Bool
isPalindrome xs = xs == (myReverse' xs)

Implement isPalindrome' again but without using reverse this time

isPalindrome' []  = True
isPalindrome' [_] = True
isPalindrome' xs  = (head xs) == (last xs) && (isPalindrome' $ init $ tail xs)

Programming Language Design Assignment #4 - HackMD