RosettaCodeData/Task/Queue-Definition/Elena/queue-definition.elena

import extensions;

class Queue<T>
{
    T[]  theArray;
    int  theTop;
    int  theTale;

    constructor()
    {
        theArray := new T[](8);
        theTop := 0;
        theTale := 0;
    }

    bool empty()
        = theTop == theTale;

    push(T object)
    {
        if (theTale > theArray.Length)
        {
            auto newArray := class Array<T>.allocate(theTale);
            class Array<T>.copy(newArray, theArray, 0, theArray.Length);

            theArray := newArray
        };

        theArray[theTale] := object;

        theTale += 1
    }

    T pop()
    {
        if (theTale == theTop)
            { InvalidOperationException.new("Queue is empty").raise() };

        T item := theArray[theTop];

        theTop += 1;

        ^ item
    }
}

public Program()
{
    Queue<int> q := new Queue<int>();
    q.push(1);
    q.push(2);
    q.push(3);
    Console.printLine(q.pop());
    Console.printLine(q.pop());
    Console.printLine(q.pop());
    Console.printLine("a queue is ", q.empty().iif("empty","not empty"));
    Console.print("Trying to pop:");
    try
    {
        q.pop()
    }
    catch(Exception e)
    {
        Console.printLine(e.Message)
    }
}