Implementation of few haskell builtins

gistfile1.hs

-- https://questhub.io/realm/haskell/quest/537bb4e2bbd0bed61d00007d

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

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

zip :: [a] -> [b] -> [(a,b)]
zip [] _ = []
zip _ [] = []
zip (x:xs) (y:ys) = (x,y) : zip xs ys

map :: (a -> b) -> [a] -> [b]
map _ [] = []
map f (x:xs) = f x : map f xs