| <html> |
| <head> |
| <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> |
| <title>Additional Features</title> |
| <link rel="stylesheet" href="../../boostbook.css" type="text/css"> |
| <meta name="generator" content="DocBook XSL Stylesheets V1.75.2"> |
| <link rel="home" href="../../index.html" title="Chapter 1. Boost.Bimap"> |
| <link rel="up" href="../rationale.html" title="Rationale"> |
| <link rel="prev" href="../rationale.html" title="Rationale"> |
| <link rel="next" href="code.html" title="Code"> |
| </head> |
| <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> |
| <table cellpadding="2" width="100%"><tr> |
| <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td> |
| <td align="center"><a href="../../../../../../index.html">Home</a></td> |
| <td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td> |
| <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> |
| <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> |
| <td align="center"><a href="../../../../../../more/index.htm">More</a></td> |
| </tr></table> |
| <hr> |
| <div class="spirit-nav"> |
| <a accesskey="p" href="../rationale.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../rationale.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="code.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_bimap.rationale.additional_features"></a><a class="link" href="additional_features.html" title="Additional Features">Additional |
| Features</a> |
| </h3></div></div></div> |
| <a name="boost_bimap.rationale.additional_features.n_1__n_n__hashed_maps"></a><h5> |
| <a name="id875074"></a> |
| <a class="link" href="additional_features.html#boost_bimap.rationale.additional_features.n_1__n_n__hashed_maps">N-1, |
| N-N, hashed maps</a> |
| </h5> |
| <p> |
| This is a very interesting point of the design. The framework introduced |
| in <span class="emphasis"><em>std::set theory</em></span> permits the management of the different |
| constraints with a very simple and conceptual approach. It is easy both to |
| remember and to learn. The idea here is to allow the user to specify the |
| collection type of each key directly. In order to implement this feature, |
| we have to solve two problems: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| The index types of the <code class="computeroutput"><span class="identifier">multi_index_container</span></code> |
| core now depends on the collection type used for each key. |
| </li> |
| <li class="listitem"> |
| The map views now change their semantics according to the collection |
| type chosen. |
| </li> |
| </ul></div> |
| <p> |
| Boost.Bimap relies heavily on Boost.MPL to implement all of the metaprogramming |
| necessary to make this framework work. By default, if the user does not specify |
| the kind of the set, a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">set</span></code> type |
| is used. |
| </p> |
| <p> |
| <span class="inlinemediaobject"><img src="../../images/bimap/bimap.structures.png" alt="bimap.structures"></span> |
| </p> |
| <a name="boost_bimap.rationale.additional_features.collection_type_of_relation_constraints"></a><h5> |
| <a name="id875189"></a> |
| <a class="link" href="additional_features.html#boost_bimap.rationale.additional_features.collection_type_of_relation_constraints">Collection |
| type of relation constraints</a> |
| </h5> |
| <p> |
| The constraints of the bimap set view are another very important feature. |
| In general, Boost.Bimap users will base the set view type on one of the two |
| collection types of their keys. It may be useful however to give this set |
| other constraints or simply to order it differently. By default, Boost.Bimap |
| bases the collection type of relations on the left collection type, but the |
| user may choose between: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| left_based |
| </li> |
| <li class="listitem"> |
| right_based |
| </li> |
| <li class="listitem"> |
| set_of_relation<> |
| </li> |
| <li class="listitem"> |
| multiset_of_relation<> |
| </li> |
| <li class="listitem"> |
| unordered_set_of_relation<> |
| </li> |
| <li class="listitem"> |
| unordered_multiset_of_relation<> |
| </li> |
| <li class="listitem"> |
| list_of |
| </li> |
| <li class="listitem"> |
| vector_of |
| </li> |
| </ul></div> |
| <p> |
| In the first two cases, there are only two indices in the <code class="computeroutput"><span class="identifier">multi_index_core</span></code>, |
| and for this reason, these are the preferred options. The implementation |
| uses further metaprogramming to define a new index if necessary. |
| </p> |
| <a name="boost_bimap.rationale.additional_features.tagged"></a><h5> |
| <a name="id875302"></a> |
| <a class="link" href="additional_features.html#boost_bimap.rationale.additional_features.tagged">Tagged</a> |
| </h5> |
| <p> |
| The idea of using tags instead of the <code class="literal">member_at::side</code> |
| idiom is very appealing since code that uses it is more readable. The only |
| cost is compile time. <span class="emphasis"><em>boost/bimap/tagged</em></span> is the implementation |
| of a non-invasive tagged idiom. The <code class="literal">relation</code> class is |
| built in such a way that even when the user uses tags, the <code class="literal">member_at::side</code> |
| idiom continues to work. This is good since an user can start tagging even |
| before completing the coding of the algorithm, and the untagged code continues |
| to work. The development becomes a little more complicated when user-defined |
| tags are included, but there are many handy metafunctions defined in the |
| <code class="literal">tagged</code> idiom that help to keep things simple enough. |
| </p> |
| <p> |
| <span class="inlinemediaobject"><img src="../../images/bimap/tagged.png" alt="tagged"></span> |
| </p> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2006 -2007 Matias Capeletto<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) |
| </p> |
| </div></td> |
| </tr></table> |
| <hr> |
| <div class="spirit-nav"> |
| <a accesskey="p" href="../rationale.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../rationale.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="code.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> |
| </div> |
| </body> |
| </html> |
