Cfrtjryk

I'm a member of a discord channel and sometimes people post simple coding exercises for fun. This time the exercise was:

Implement the following operations of a queue using stacks.

• push(x) -- Push element x to the back of queue.


• pop() -- Removes the element from in front of queue.


• peek() -- Get the front element.


• empty() -- Return whether the queue is empty

Example:

MyQueue queue = new MyQueue();



queue.push(1);

queue.push(2);

queue.peek(); // returns 1

queue.pop(); // returns 1

queue.empty(); // returns false

I didn't implement it using stacks because I don't know of any that are in the standard Haskell library but

I came up with this Solution:

data Queue a = Empty | Value a (Queue a) deriving (Show, Eq, Read)



push :: a -> Queue a -> Queue a

push x Empty             = Value x Empty

push x (Value a pointer) = Value a (push x pointer)



pop :: Queue a -> Maybe (a, Queue a)

pop Empty             = Nothing

pop (Value a pointer) = Just (a, pointer)



peek :: Queue a -> Maybe a

peek Empty       = Nothing

peek (Value a _) = Just a 



empty :: Queue a -> Bool

empty Empty = True

empty _     = False

I'm currently trying to understand Haskell better and was wondering if there was a more idiomatic Solution.