// -*- mode: c++; mode: visual-line; mode: flyspell; fill-column: 100000 -*-
/***************************************************************************
 *  doc/tutorial_deque.dox
 *
 *  Usage Tutorial for STXXL
 *
 *  Part of the STXXL. See http://stxxl.sourceforge.net
 *
 *  Copyright (C) 2013 Timo Bingmann <tb@panthema.net>
 *  Copyright (C) 2013 Daniel Feist <daniel.feist@student.kit.edu>
 *
 *  Distributed under the Boost Software License, Version 1.0.
 *  (See accompanying file LICENSE_1_0.txt or copy at
 *  http://www.boost.org/LICENSE_1_0.txt)
 **************************************************************************/

namespace stxxl {

/** \page tutorial_deque STXXL Deque

This page introduces into the stxxl::deque container (to learn more about the structure of stxxl::deque, see section \ref design_deque).

The acronym Deque stands for "double-ended-queue", that means elements can be accessed, inserted and deleted on both ends of the data structure - in contrast to the stxxl::queue (see \ref tutorial_queue),
where that's only possible on one of the two endings.


### Creating a STXXL deque

To create a stxxl::deque object, only the data value type must be specified:

\code
typedef stxxl::deque<int> deque;
deque my_deque;
\endcode

See \ref stxxl::deque for additional template parameter details.

### Insert elements

Inserting elements is possible at the start (by calling the push_front() function) as well as the end (by calling the push_back() function) of the deque.

\code
my_deque.push_front(2);
my_deque.push_front(11);

my_deque.push_back(5);
my_deque.push_back(8);

// deque now stores: |11|2|5|8|
\endcode


### Access elements

To return a reference to the element at the start of the deque, call front(), to return a reference to the elemtent at the end of the deque, call back() on a deque instance.

\code
std::cout << "return 'first' element: " << my_deque.front() << std::endl;  // prints 11
std::cout << "return 'last' element: " << my_deque.back() << std::endl;  // prints 8
\endcode

Accessing elements at random is supported by the STXXL deque with the []-operator like the following.

\code
std::cout << "random access: " << my_deque[2] << std::endl;  // prints 5
\endcode

The operations described in this sections are not I/O-efficient as they come with \f$\mathcal{O}(1)\f$ time per I/O-access. To achieve I/O-efficient scanning, the STXXL deque provides different iterators.
The simplest iterator can be used as follows:

\code
// create forward-iterator (which advances from start to end)
stxxl::deque_iterator<deque> deque_iterator = my_deque.begin();
// access item at current iterator position
std::cout << *deque_iterator << std::endl;
// move up one step by preincrement
++deque_iterator;
\endcode

### Delete elements

Deleting elements is possible at both endings of the deque by using pop_front() and pop_back():

\code
my_deque.pop_front();  // deque now stores: |2|5|8|
my_deque.pop_back();  // deque now stores: |2|5|
\endcode


### Determine size / Check whether the deque is empty

To determine the size (i.e. the number of elements) of an instance, call size():

\code
std::cout << "deque stores: " << my_deque.size() << " elements" << std::endl;
\endcode

To check if the deque is empty, call empty() which returns true if the deque is empty:

\code
std::cout << "empty deque? " << my_deque.empty() << std::endl;
\endcode

### A minimal example on STXXL's deque

(See \ref examples/containers/deque1.cpp for the sourcecode of the following example).

\snippet examples/containers/deque1.cpp example

See \ref examples/containers/deque2.cpp for the sourcecode of a more comprehensive example.

\example examples/containers/deque1.cpp
This example code is explained in the \ref tutorial_deque section.

\example examples/containers/deque2.cpp
This example code is explained in the \ref tutorial_deque section.

*/

} // namespace stxxl