CircularQueue 1.0

Module Module1
    Structure CircularQueue
        Dim Rear As Integer
        Dim Front As Integer
        Dim Elements As String()
        Dim MaxLength As Integer
    End Structure

    Function IsEmpty(MyQueue As CircularQueue) As Boolean
        If MyQueue.Rear = -1 And MyQueue.Front = -1 Then
            Return True
        Else : Return False
        End If
    End Function

    Function IsFull(MyQueue As CircularQueue) As Boolean
        If MyQueue.Front = (MyQueue.Rear + 1) Mod MyQueue.MaxLength Then
            Return True
        Else : Return False
        End If
    End Function

    Function Peek(MyQueue As CircularQueue) As String
        If Not IsEmpty(MyQueue) Then
            Return MyQueue.Elements(MyQueue.Front Mod MyQueue.MaxLength)
        End If
        Return ""
    End Function

    Function Dequeue(ByRef MyQueue As CircularQueue) As String
        Dim RemovedElement As String = Peek(MyQueue)
        If IsEmpty(MyQueue) Then
            Console.WriteLine("Stack Underflow")
        ElseIf MyQueue.Rear = MyQueue.Front Then
            MyQueue.Rear = -1
            MyQueue.Front = -1
        Else : MyQueue.Front = (MyQueue.Front + 1) Mod MyQueue.MaxLength
        End If
        Return RemovedElement
    End Function

    Sub Main()
        Dim DocumentsToPrint As CircularQueue
        InitialiseQueue(DocumentsToPrint, 5)

        'manipulate the print queue with any of
        'these functions and procedures

        Console.ReadLine()
    End Sub

    Sub InitialiseQueue(ByRef MyQueue As CircularQueue, QueueSize As Integer)
        MyQueue.Rear = -1
        MyQueue.Front = -1
        ReDim MyQueue.Elements(QueueSize - 1)
        MyQueue.MaxLength = QueueSize
    End Sub

    Sub Enqueue(ByRef MyQueue As CircularQueue, NewElement As String)
        If IsFull(MyQueue) Then
            Console.WriteLine("Stack Overflow")
            Exit Sub
        ElseIf IsEmpty(MyQueue) Then
            MyQueue.Rear = 0
            MyQueue.Front = 0
        Else
            MyQueue.Rear = (MyQueue.Rear + 1) Mod MyQueue.MaxLength
        End If
        MyQueue.Elements(MyQueue.Rear) = NewElement
    End Sub

    Sub PrintCQueue(MyQueue As CircularQueue)
        If Not IsEmpty(MyQueue) Then
            Dim i As Integer = MyQueue.Front
            Do
                Console.WriteLine(MyQueue.Elements(i))
                If i = MyQueue.Rear Then
                    Exit Sub
                End If
                i = (i + 1) Mod MyQueue.MaxLength
            Loop Until i = MyQueue.Front
        End If
    End Sub

End Module