Mastering Delphi Programming: A Complete Reference Guide

Implementing a queue with a list

For a more meaningful example, we can see how we can adapt code that expects to operate on a double-ended queue when we don't have an implementation of such a structure ready.

A double-ended queue, or deque, is a queue that allows you to add and remove elements both at the front and at the back of the queue.

The AdapterMain unit implements two methods, RotateLeft and RotateRight, as follows:

procedure TfrmAdapter.RotateLeft(const deque: IDeque<integer>);begin  deque.PushBack(deque.PopFront);end;procedure TfrmAdapter.RotateRight(const deque: IDeque<integer>);begin  deque.PushFront(deque.PopBack);end;

Both are using the following double-ended queue interface from Deque.Intf:

type  IDeque<T> = interface function ...