Generic Stack Implementation using protocol approach

Stack.swift

import CoreFoundation

//Generic Type Protocol
public protocol Stackable {
    //Generic Type
    associatedtype E

    // Push - add new element to stack array
    mutating func push(_ element: E)

    // Pop - remove and return last element of array
    mutating func pop() -> E?

    // Peek - return last element of array
    func peek() -> E?

    //count the number of element in stack
    var count : Int { get }

    //check for empty stack list
    var isEmpty: Bool { get }
}

//Stack Implementation
public struct Stack<T> : Stackable {
    var items = [T]()

    //init with array items
    init(_ elements : [T]) {
        items = elements
    }
    // Push - add new element to stack array
    mutating public func push(_ element: T) {
        items.append(element)
    }

    // Pop - remove and return last element of array
    mutating public func pop() -> T? {
        items.popLast()
    }

    // Peek - return last element of array
    public func peek() -> T? {
        items.last
    }

    //count the number of element in stack
    public var count : Int {
        items.count
    }

    //check for empty stack list
    public var isEmpty: Bool { items.isEmpty }
}

//create stack using array literal
extension Stack : ExpressibleByArrayLiteral {
    public init(arrayLiteral elements: T...) {
        items = elements
    }
}

//customize stack description by implement CustomStringConvertible protocol
extension Stack : CustomStringConvertible {
    public var description: String {
        return items.map {"\($0)" }.joined(separator: " ")
    }
}
//create stack (string type) object using standard init method
var stringStackWithInit  = Stack<String>()
stringStackWithInit.push("swift")
stringStackWithInit.push("5")

//create stack (string type) object using init with array
var stringStackWithInitArray  = Stack<String>(["swift","5"])

//create stack (string type) object expressible by array literal
var stringStackArray : Stack  = ["swift","5"]

print(stringStackWithInit.description)
print(stringStackWithInitArray.description)
print(stringStackArray.description)