Home Explore Help
Register Sign In
devn00b
/
EQ2EMu
9
3
Fork 0
Files Issues 69 Pull Requests 0 Wiki
Tree: 231c866c2c
Branches Tags
EQ2EMu
/
EQ2
/
source
/
depends
/
boost_1_72_0
/
libs
/
hana
/
doc
/
html
/
structboost_1_1hana_1_1map.html

structboost_1_1hana_1_1map.html 97 KB
History Raw

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400401402403404405406407408409410411412413414415416417418419420421422423424425426427428429430431432433434435436437438439440441442443444445446447448449450451452453454455456457458459460461462463464465466467468469470471472473474475476477478479480481482483484485486487488489490491492493494495496497498499500501502503504505506507508509510511512513514515516517518519520521522523524525526527528529530531532533534535536537538539540541542543544545546547548549550551552553554555556557558559560561562563564565566567568569570571572573574575576577578579580581582583584585586587588589590591592593594595596597598599600601602603604605 
  1. <!--
    2. 

  2. Copyright Louis Dionne 2013-2017
    3. 

  3. Distributed under the Boost Software License, Version 1.0.
    4. 

  4. (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
    5. 

  5. -->
    6. 

  6. <!-- boost-no-inspect -->
    7. 

  7. <!-- HTML header for doxygen 1.8.9.1-->
    8. 

  8. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    9. 

  9. <html xmlns="http://www.w3.org/1999/xhtml">
    10. 

  10. <head>
    11. 

  11. <meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/>
    12. 

  12. <meta http-equiv="X-UA-Compatible" content="IE=9"/>
    13. 

  13. <meta name="generator" content="Doxygen 1.8.15"/>
    14. 

  14. <title>Boost.Hana: boost::hana::map&lt; Pairs &gt; Struct Template Reference</title>
    15. 

  15. <link href="tabs.css" rel="stylesheet" type="text/css"/>
    16. 

  16. <script type="text/javascript" src="jquery.js"></script>
    17. 

  17. <script type="text/javascript" src="dynsections.js"></script>
    18. 

  18. <link href="navtree.css" rel="stylesheet" type="text/css"/>
    19. 

  19. <script type="text/javascript" src="resize.js"></script>
    20. 

  20. <script type="text/javascript" src="navtreedata.js"></script>
    21. 

  21. <script type="text/javascript" src="navtree.js"></script>
    22. 

  22. <script type="text/javascript">
    23. 

  23. /* @license magnet:?xt=urn:btih:cf05388f2679ee054f2beb29a391d25f4e673ac3&amp;dn=gpl-2.0.txt GPL-v2 */
    24. 

  24.   $(document).ready(initResizable);
    25. 

  25. /* @license-end */</script>
    26. 

  26. <link href="search/search.css" rel="stylesheet" type="text/css"/>
    27. 

  27. <script type="text/javascript" src="search/searchdata.js"></script>
    28. 

  28. <script type="text/javascript" src="search/search.js"></script>
    29. 

  29. <script type="text/javascript">
    30. 

  30. /* @license magnet:?xt=urn:btih:cf05388f2679ee054f2beb29a391d25f4e673ac3&amp;dn=gpl-2.0.txt GPL-v2 */
    31. 

  31.   $(document).ready(function() { init_search(); });
    32. 

  32. /* @license-end */
    33. 

  33. </script>
    34. 

  34. <script type="text/x-mathjax-config">
    35. 

  35.   MathJax.Hub.Config({
    36. 

  36.     extensions: ["tex2jax.js"],
    37. 

  37.     jax: ["input/TeX","output/HTML-CSS"],
    38. 

  38. });
    39. 

  39. // Copyright Louis Dionne 2013-2017
    40. 

  40. // Distributed under the Boost Software License, Version 1.0.
    41. 

  41. // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
    42. 

  42. MathJax.Hub.Config({
    43. 

  43.     "HTML-CSS": {
    44. 

  44.         linebreaks: {
    45. 

  45.             automatic: true,
    46. 

  46.             width: "75% container"
    47. 

  47.         }
    48. 

  48.     }
    49. 

  49. });
    50. 

  50. </script><script type="text/javascript" async="async" src="https://cdn.mathjax.org/mathjax/latest/MathJax.js"></script>
    51. 

  51. <link href="doxygen.css" rel="stylesheet" type="text/css" />
    52. 

  52. <!-- Additional javascript for drawing charts. -->
    53. 

  53. <script type="text/javascript" src="highcharts.js"></script>
    54. 

  54. <script type="text/javascript" src="highcharts-data.js"></script>
    55. 

  55. <script type="text/javascript" src="highcharts-exporting.js"></script>
    56. 

  56. <script type="text/javascript" src="chart.js"></script>
    57. 

  57. <script type="text/javascript" src="hana.js"></script>
    58. 

  58. </head>
    59. 

  59. <body>
    60. 

  60. <div id="top"><!-- do not remove this div, it is closed by doxygen! -->
    61. 

  61. <div id="titlearea">
    62. 

  62. <table cellspacing="0" cellpadding="0">
    63. 

  63.  <tbody>
    64. 

  64.  <tr style="height: 56px;">
    65. 

  65.   <td id="projectlogo"><img alt="Logo" src="Boost.png"/></td>
    66. 

  66.   <td style="padding-left: 0.5em;">
    67. 

  67.    <div id="projectname">Boost.Hana
    68. 

  68.    &#160;<span id="projectnumber">1.6.0</span>
    69. 

  69.    </div>
    70. 

  70.    <div id="projectbrief">Your standard library for metaprogramming</div>
    71. 

  71.   </td>
    72. 

  72.    <td>        <div id="MSearchBox" class="MSearchBoxInactive">
    73. 

  73.         <span class="left">
    74. 

  74.           <img id="MSearchSelect" src="search/mag_sel.png"
    75. 

  75.                onmouseover="return searchBox.OnSearchSelectShow()"
    76. 

  76.                onmouseout="return searchBox.OnSearchSelectHide()"
    77. 

  77.                alt=""/>
    78. 

  78.           <input type="text" id="MSearchField" value="Search" accesskey="S"
    79. 

  79.                onfocus="searchBox.OnSearchFieldFocus(true)" 
    80. 

  80.                onblur="searchBox.OnSearchFieldFocus(false)" 
    81. 

  81.                onkeyup="searchBox.OnSearchFieldChange(event)"/>
    82. 

  82.           </span><span class="right">
    83. 

  83.             <a id="MSearchClose" href="javascript:searchBox.CloseResultsWindow()"><img id="MSearchCloseImg" border="0" src="search/close.png" alt=""/></a>
    84. 

  84.           </span>
    85. 

  85.         </div>
    86. 

  86. </td>
    87. 

  87.  </tr>
    88. 

  88.  </tbody>
    89. 

  89. </table>
    90. 

  90. </div>
    91. 

  91. <!-- end header part -->
    92. 

  92. <!-- Generated by Doxygen 1.8.15 -->
    93. 

  93. <script type="text/javascript">
    94. 

  94. /* @license magnet:?xt=urn:btih:cf05388f2679ee054f2beb29a391d25f4e673ac3&amp;dn=gpl-2.0.txt GPL-v2 */
    95. 

  95. var searchBox = new SearchBox("searchBox", "search",false,'Search');
    96. 

  96. /* @license-end */
    97. 

  97. </script>
    98. 

  98. </div><!-- top -->
    99. 

  99. <div id="side-nav" class="ui-resizable side-nav-resizable">
    100. 

  100.   <div id="nav-tree">
    101. 

  101.     <div id="nav-tree-contents">
    102. 

  102.       <div id="nav-sync" class="sync"></div>
    103. 

  103.     </div>
    104. 

  104.   </div>
    105. 

  105.   <div id="splitbar" style="-moz-user-select:none;" 
    106. 

  106.        class="ui-resizable-handle">
    107. 

  107.   </div>
    108. 

  108. </div>
    109. 

  109. <script type="text/javascript">
    110. 

  110. /* @license magnet:?xt=urn:btih:cf05388f2679ee054f2beb29a391d25f4e673ac3&amp;dn=gpl-2.0.txt GPL-v2 */
    111. 

  111. $(document).ready(function(){initNavTree('structboost_1_1hana_1_1map.html','');});
    112. 

  112. /* @license-end */
    113. 

  113. </script>
    114. 

  114. <div id="doc-content">
    115. 

  115. <!-- window showing the filter options -->
    116. 

  116. <div id="MSearchSelectWindow"
    117. 

  117.      onmouseover="return searchBox.OnSearchSelectShow()"
    118. 

  118.      onmouseout="return searchBox.OnSearchSelectHide()"
    119. 

  119.      onkeydown="return searchBox.OnSearchSelectKey(event)">
    120. 

  120. </div>
    121. 

  121. 

  122. <!-- iframe showing the search results (closed by default) -->
    123. 

  123. <div id="MSearchResultsWindow">
    124. 

  124. <iframe src="javascript:void(0)" frameborder="0" 
    125. 

  125.         name="MSearchResults" id="MSearchResults">
    126. 

  126. </iframe>
    127. 

  127. </div>
    128. 

  128. 

  129. <div class="header">
    130. 

  130.   <div class="summary">
    131. 

  131. <a href="#related">Synopsis of associated functions</a> &#124;
    132. 

  132. <a href="#friends">Friends</a> &#124;
    133. 

  133. <a href="#pub-methods">Public Member Functions</a> &#124;
    134. 

  134. <a href="structboost_1_1hana_1_1map-members.html">List of all members</a>  </div>
    135. 

  135.   <div class="headertitle">
    136. 

  136. <div class="title">boost::hana::map&lt; Pairs &gt; Struct Template Reference<div class="ingroups"><a class="el" href="group__group-datatypes.html">Data types</a></div></div>  </div>
    137. 

  137. </div><!--header-->
    138. 

  138. <div class="contents">
    139. 

  139. <a name="details" id="details"></a><h2 class="groupheader">Description</h2>
    140. 

  140. <div class="textblock"><h3>template&lt;typename ... Pairs&gt;<br />
    141. 

  141. struct boost::hana::map&lt; Pairs &gt;</h3>
    142. 

  142. 

  143. <p>Basic associative container requiring unique, <code>Comparable</code> and <code>Hashable</code> keys. </p>
    144. 

  144. <p>The order of the elements of the map is unspecified. Also, all the keys must be <code>Hashable</code>, and any two keys with equal hashes must be <code>Comparable</code> with each other at compile-time.</p>
    145. 

  145. <dl class="section note"><dt>Note</dt><dd>The actual representation of a <code><a class="el" href="structboost_1_1hana_1_1map.html" title="Basic associative container requiring unique, Comparable and Hashable keys.">hana::map</a></code> is an implementation detail. As such, one should not assume anything more than what is explicitly documented as being part of the interface of a map, such as:<ul>
    146. 

  146. <li>the presence of additional constructors</li>
    147. 

  147. <li>the presence of additional assignment operators</li>
    148. 

  148. <li>the fact that <code><a class="el" href="structboost_1_1hana_1_1map.html" title="Basic associative container requiring unique, Comparable and Hashable keys.">hana::map</a>&lt;Pairs...&gt;</code> is, or is not, a dependent type</li>
    149. 

  149. </ul>
    150. 

  150. In particular, the last point is very important; <code><a class="el" href="structboost_1_1hana_1_1map.html" title="Basic associative container requiring unique, Comparable and Hashable keys.">hana::map</a>&lt;Pairs...&gt;</code> is basically equivalent to <div class="fragment"><div class="line">decltype(hana::make_pair(std::declval&lt;Pairs&gt;()...))</div></div><!-- fragment --> which is not something that can be pattern-matched on during template argument deduction, for example. More details <a class="el" href="index.html#tutorial-containers-types">in the tutorial</a>.</dd></dl>
    151. 

  151. <h2>Modeled concepts </h2>
    152. 

  152. <ol type="1">
    153. 

  153. <li><code>Comparable</code><br />
    154. 

  154. Two maps are equal iff all their keys are equal and are associated to equal values. <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>&gt;</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;string&gt;</span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"><span class="keyword">using namespace </span>std::literals;</div><div class="line"></div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() {</div><div class="line">    <a class="code" href="group__group-assertions.html#ga4796ae107d58b67e0bbccd5ae6f70101">BOOST_HANA_RUNTIME_CHECK</a>(</div><div class="line">        hana::make_map(</div><div class="line">            hana::make_pair(hana::char_c&lt;&#39;a&#39;&gt;, <span class="stringliteral">&quot;foobar&quot;</span>s),</div><div class="line">            hana::make_pair(hana::type_c&lt;int&amp;&amp;&gt;, <span class="keyword">nullptr</span>)</div><div class="line">        )</div><div class="line">        ==</div><div class="line">        hana::make_map(</div><div class="line">            hana::make_pair(hana::type_c&lt;int&amp;&amp;&gt;, (<span class="keywordtype">void</span>*)0),</div><div class="line">            hana::make_pair(hana::char_c&lt;&#39;a&#39;&gt;, <span class="stringliteral">&quot;foobar&quot;</span>s)</div><div class="line">        )</div><div class="line">    );</div><div class="line">}</div></div><!-- fragment --></li>
    155. 

  155. <li><code>Searchable</code><br />
    156. 

  156. A map can be searched by its keys with a predicate yielding a compile-time <code>Logical</code>. Also note that <code>operator[]</code> can be used instead of <code>at_key</code>. <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="at__key_8hpp.html">boost/hana/at_key.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="equal_8hpp.html">boost/hana/equal.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="find_8hpp.html">boost/hana/find.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="optional_8hpp.html">boost/hana/optional.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>&gt;</span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"></div><div class="line"></div><div class="line">constexpr <span class="keyword">auto</span> m = hana::make_map(</div><div class="line">    hana::make_pair(hana::type_c&lt;int&gt;, <span class="charliteral">&#39;i&#39;</span>),</div><div class="line">    hana::make_pair(hana::type_c&lt;float&gt;, <span class="charliteral">&#39;f&#39;</span>)</div><div class="line">);</div><div class="line">static_assert(<a class="code" href="group__group-Searchable.html#ga6b6cdd69942b0fe3bf5254247f9c861e">hana::find</a>(m, hana::type_c&lt;int&gt;) == hana::just(<span class="charliteral">&#39;i&#39;</span>), <span class="stringliteral">&quot;&quot;</span>);</div><div class="line">static_assert(<a class="code" href="group__group-Searchable.html#ga6b6cdd69942b0fe3bf5254247f9c861e">hana::find</a>(m, hana::type_c&lt;float&gt;) == hana::just(<span class="charliteral">&#39;f&#39;</span>), <span class="stringliteral">&quot;&quot;</span>);</div><div class="line"><a class="code" href="group__group-assertions.html#ga2c5006540936d9f8880e3a39f4fcc035">BOOST_HANA_CONSTANT_CHECK</a>(<a class="code" href="group__group-Searchable.html#ga6b6cdd69942b0fe3bf5254247f9c861e">hana::find</a>(m, hana::type_c&lt;void&gt;) == hana::nothing);</div><div class="line"><a class="code" href="group__group-assertions.html#ga2c5006540936d9f8880e3a39f4fcc035">BOOST_HANA_CONSTANT_CHECK</a>(<a class="code" href="group__group-Searchable.html#ga6b6cdd69942b0fe3bf5254247f9c861e">hana::find</a>(m, hana::int_c&lt;3&gt;) == hana::nothing);</div><div class="line"></div><div class="line"><span class="comment">// operator[] is equivalent to at_key</span></div><div class="line">static_assert(m[hana::type_c&lt;int&gt;] == <span class="charliteral">&#39;i&#39;</span>, <span class="stringliteral">&quot;&quot;</span>);</div><div class="line">static_assert(m[hana::type_c&lt;float&gt;] == <span class="charliteral">&#39;f&#39;</span>, <span class="stringliteral">&quot;&quot;</span>);</div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() { }</div></div><!-- fragment --></li>
    157. 

  157. <li><code>Foldable</code><br />
    158. 

  158. Folding a map is equivalent to folding a list of the key/value pairs it contains. In particular, since that list is not guaranteed to be in any specific order, folding a map with an operation that is not both commutative and associative will yield non-deterministic behavior. <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="first_8hpp.html">boost/hana/first.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="fold__left_8hpp.html">boost/hana/fold_left.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="insert_8hpp.html">boost/hana/insert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="second_8hpp.html">boost/hana/second.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>&gt;</span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"></div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() {</div><div class="line">    <span class="comment">// Given a map of (key, value) pairs, returns a map of (value, key) pairs.</span></div><div class="line">    <span class="comment">// This requires both the keys and the values to be compile-time Comparable.</span></div><div class="line">    <span class="keyword">auto</span> invert = [](<span class="keyword">auto</span> <a class="code" href="structboost_1_1hana_1_1map.html#a1ee432be0bd10f08a637a437e311e4e2">map</a>) {</div><div class="line">        <span class="keywordflow">return</span> <a class="code" href="group__group-Foldable.html#ga38c6b3f6b1cbadb9b8432a05ff16b7d2">hana::fold_left</a>(<a class="code" href="structboost_1_1hana_1_1map.html#a1ee432be0bd10f08a637a437e311e4e2">map</a>, hana::make_map(), [](<span class="keyword">auto</span> <a class="code" href="structboost_1_1hana_1_1map.html#a1ee432be0bd10f08a637a437e311e4e2">map</a>, <span class="keyword">auto</span> pair) {</div><div class="line">            <span class="keywordflow">return</span> <a class="code" href="group__group-Sequence.html#gae22a1a184b1b2dd550fa4fa619bed2e9">hana::insert</a>(<a class="code" href="structboost_1_1hana_1_1map.html#a1ee432be0bd10f08a637a437e311e4e2">map</a>, hana::make_pair(<a class="code" href="group__group-Product.html#ga7bb979d59ffc3ab862cb7d9dc7730077">hana::second</a>(pair), <a class="code" href="group__group-Product.html#ga34bbf4281de06dc3540441e8b2bd24f4">hana::first</a>(pair)));</div><div class="line">        });</div><div class="line">    };</div><div class="line"></div><div class="line">    <span class="keyword">auto</span> m = hana::make_map(</div><div class="line">        hana::make_pair(hana::type_c&lt;int&gt;, hana::int_c&lt;1&gt;),</div><div class="line">        hana::make_pair(hana::type_c&lt;float&gt;, hana::int_c&lt;2&gt;),</div><div class="line">        hana::make_pair(hana::int_c&lt;3&gt;, hana::type_c&lt;void&gt;)</div><div class="line">    );</div><div class="line"></div><div class="line">    <a class="code" href="group__group-assertions.html#ga2c5006540936d9f8880e3a39f4fcc035">BOOST_HANA_CONSTANT_CHECK</a>(invert(m) ==</div><div class="line">        hana::make_map(</div><div class="line">            hana::make_pair(hana::int_c&lt;1&gt;, hana::type_c&lt;int&gt;),</div><div class="line">            hana::make_pair(hana::int_c&lt;2&gt;, hana::type_c&lt;float&gt;),</div><div class="line">            hana::make_pair(hana::type_c&lt;void&gt;, hana::int_c&lt;3&gt;)</div><div class="line">        )</div><div class="line">    );</div><div class="line">}</div></div><!-- fragment --></li>
    159. 

  159. </ol>
    160. 

  160. <h2>Conversion from any <code>Foldable</code> </h2>
    161. 

  161. <p>Any <code>Foldable</code> of <code>Product</code>s can be converted to a <code><a class="el" href="structboost_1_1hana_1_1map.html" title="Basic associative container requiring unique, Comparable and Hashable keys.">hana::map</a></code> with <code><a class="el" href="group__group-core.html#gadc70755c1d059139297814fb3bfeb91e" title="Converts an object from one data type to another.">hana::to</a>&lt;<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps.">hana::map_tag</a>&gt;</code> or, equivalently, <code>hana::to_map</code>. If the <code>Foldable</code> contains duplicate keys, only the value associated to the first occurence of each key is kept. </p><div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="core_2to_8hpp.html">boost/hana/core/to.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="tuple_8hpp.html">boost/hana/tuple.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>&gt;</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;string&gt;</span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"><span class="keyword">using namespace </span>std::literals;</div><div class="line"></div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() {</div><div class="line">    <span class="keyword">auto</span> xs = hana::make_tuple(</div><div class="line">        hana::make_pair(hana::type_c&lt;int&gt;, <span class="stringliteral">&quot;abcd&quot;</span>s),</div><div class="line">        hana::make_pair(hana::type_c&lt;void&gt;, 1234),</div><div class="line">        hana::make_pair(hana::type_c&lt;int&gt;, <span class="keyword">nullptr</span>)</div><div class="line">    );</div><div class="line"></div><div class="line">    <a class="code" href="group__group-assertions.html#ga4796ae107d58b67e0bbccd5ae6f70101">BOOST_HANA_RUNTIME_CHECK</a>(</div><div class="line">        hana::to&lt;hana::map_tag&gt;(xs) == hana::make_map(</div><div class="line">            hana::make_pair(hana::type_c&lt;int&gt;, <span class="stringliteral">&quot;abcd&quot;</span>s),</div><div class="line">            hana::make_pair(hana::type_c&lt;void&gt;, 1234)</div><div class="line">        )</div><div class="line">    );</div><div class="line">}</div></div><!-- fragment --><h2>Example </h2>
    162. 

  162. <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="at__key_8hpp.html">boost/hana/at_key.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="contains_8hpp.html">boost/hana/contains.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="string_8hpp.html">boost/hana/string.hpp</a>&gt;</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;functional&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;string&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;vector&gt;</span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"></div><div class="line"></div><div class="line"><span class="keyword">template</span> &lt;<span class="keyword">typename</span> ...Events&gt;</div><div class="line"><span class="keyword">struct </span>event_system {</div><div class="line">    <span class="keyword">using</span> Callback = std::function&lt;void()&gt;;</div><div class="line">    hana::map&lt;hana::pair&lt;Events, std::vector&lt;Callback&gt;&gt;...&gt; map_;</div><div class="line"></div><div class="line">    <span class="keyword">template</span> &lt;<span class="keyword">typename</span> Event, <span class="keyword">typename</span> F&gt;</div><div class="line">    <span class="keywordtype">void</span> <a class="code" href="group__group-functional.html#ga35c4fc3c5677b9f558150b90e74d3ab1">on</a>(Event e, F handler) {</div><div class="line">        <span class="keyword">auto</span> is_known_event = <a class="code" href="group__group-Searchable.html#ga38e7748956cbc9f3d9bb035ac8577906">hana::contains</a>(map_, e);</div><div class="line">        static_assert(is_known_event,</div><div class="line">            <span class="stringliteral">&quot;trying to add a handler to an unknown event&quot;</span>);</div><div class="line"></div><div class="line">        map_[e].push_back(handler);</div><div class="line">    }</div><div class="line"></div><div class="line">    <span class="keyword">template</span> &lt;<span class="keyword">typename</span> Event&gt;</div><div class="line">    <span class="keywordtype">void</span> trigger(Event e)<span class="keyword"> const </span>{</div><div class="line">        <span class="keyword">auto</span> is_known_event = <a class="code" href="group__group-Searchable.html#ga38e7748956cbc9f3d9bb035ac8577906">hana::contains</a>(map_, e);</div><div class="line">        static_assert(is_known_event,</div><div class="line">            <span class="stringliteral">&quot;trying to trigger an unknown event&quot;</span>);</div><div class="line"></div><div class="line">        <span class="keywordflow">for</span> (<span class="keyword">auto</span>&amp; handler : this-&gt;map_[e])</div><div class="line">            handler();</div><div class="line">    }</div><div class="line">};</div><div class="line"></div><div class="line"><span class="keyword">template</span> &lt;<span class="keyword">typename</span> ...Events&gt;</div><div class="line">event_system&lt;Events...&gt; make_event_system(Events ...events) {</div><div class="line">    <span class="keywordflow">return</span> {};</div><div class="line">}</div><div class="line"></div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() {</div><div class="line">    <span class="keyword">auto</span> events = make_event_system(</div><div class="line">        BOOST_HANA_STRING(<span class="stringliteral">&quot;foo&quot;</span>),</div><div class="line">        BOOST_HANA_STRING(<span class="stringliteral">&quot;bar&quot;</span>),</div><div class="line">        BOOST_HANA_STRING(<span class="stringliteral">&quot;baz&quot;</span>)</div><div class="line">    );</div><div class="line"></div><div class="line">    std::vector&lt;std::string&gt; triggered_events;</div><div class="line">    events.on(BOOST_HANA_STRING(<span class="stringliteral">&quot;foo&quot;</span>), [&amp;] {</div><div class="line">        triggered_events.push_back(<span class="stringliteral">&quot;foo:1&quot;</span>);</div><div class="line">    });</div><div class="line">    events.on(BOOST_HANA_STRING(<span class="stringliteral">&quot;foo&quot;</span>), [&amp;] {</div><div class="line">        triggered_events.push_back(<span class="stringliteral">&quot;foo:2&quot;</span>);</div><div class="line">    });</div><div class="line">    events.on(BOOST_HANA_STRING(<span class="stringliteral">&quot;bar&quot;</span>), [&amp;] {</div><div class="line">        triggered_events.push_back(<span class="stringliteral">&quot;bar:1&quot;</span>);</div><div class="line">    });</div><div class="line">    events.on(BOOST_HANA_STRING(<span class="stringliteral">&quot;baz&quot;</span>), [&amp;] {</div><div class="line">        triggered_events.push_back(<span class="stringliteral">&quot;baz:1&quot;</span>);</div><div class="line">    });</div><div class="line"></div><div class="line">    events.trigger(BOOST_HANA_STRING(<span class="stringliteral">&quot;foo&quot;</span>));</div><div class="line">    events.trigger(BOOST_HANA_STRING(<span class="stringliteral">&quot;bar&quot;</span>));</div><div class="line">    events.trigger(BOOST_HANA_STRING(<span class="stringliteral">&quot;baz&quot;</span>));</div><div class="line"></div><div class="line">    <a class="code" href="group__group-assertions.html#ga4796ae107d58b67e0bbccd5ae6f70101">BOOST_HANA_RUNTIME_CHECK</a>(triggered_events == std::vector&lt;std::string&gt;{</div><div class="line">        <span class="stringliteral">&quot;foo:1&quot;</span>, <span class="stringliteral">&quot;foo:2&quot;</span>, <span class="stringliteral">&quot;bar:1&quot;</span>, <span class="stringliteral">&quot;baz:1&quot;</span></div><div class="line">    });</div><div class="line">}</div></div><!-- fragment --> </div><table class="memberdecls">
    163. 

  163. <tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="related"></a>
    164. 

  164. Synopsis of associated functions</h2></td></tr>
    165. 

  165. <tr class="memitem:a409d52de54cc7e55eca1a7b5dda4ce30"><td class="memTemplParams" colspan="2">template&lt;&gt; </td></tr>
    166. 

  166. <tr class="memitem:a409d52de54cc7e55eca1a7b5dda4ce30"><td class="memTemplItemLeft" align="right" valign="top">constexpr auto&#160;</td><td class="memTemplItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a409d52de54cc7e55eca1a7b5dda4ce30">make&lt; map_tag &gt;</a></td></tr>
    167. 

  167. <tr class="memdesc:a409d52de54cc7e55eca1a7b5dda4ce30"><td class="mdescLeft">&#160;</td><td class="mdescRight">Function object for creating a <code><a class="el" href="structboost_1_1hana_1_1map.html" title="Basic associative container requiring unique, Comparable and Hashable keys.">hana::map</a></code>.  <a href="#a409d52de54cc7e55eca1a7b5dda4ce30">More...</a><br /></td></tr>
    168. 

  168. <tr class="separator:a409d52de54cc7e55eca1a7b5dda4ce30"><td class="memSeparator" colspan="2">&#160;</td></tr>
    169. 

  169. <tr class="memitem:ae73cf43ee56352e4c25984b0fe3c3d04"><td class="memItemLeft" align="right" valign="top">constexpr auto&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#ae73cf43ee56352e4c25984b0fe3c3d04">make_map</a> = <a class="el" href="group__group-core.html#ga1d92480f0af1029878e773dafa3e2f60">make</a>&lt;<a class="el" href="structboost_1_1hana_1_1map__tag.html">map_tag</a>&gt;</td></tr>
    170. 

  170. <tr class="memdesc:ae73cf43ee56352e4c25984b0fe3c3d04"><td class="mdescLeft">&#160;</td><td class="mdescRight">Alias to <code>make&lt;<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps.">map_tag</a>&gt;</code>; provided for convenience.  <a href="#ae73cf43ee56352e4c25984b0fe3c3d04">More...</a><br /></td></tr>
    171. 

  171. <tr class="separator:ae73cf43ee56352e4c25984b0fe3c3d04"><td class="memSeparator" colspan="2">&#160;</td></tr>
    172. 

  172. <tr class="memitem:a4feb32bd0a065a0732908716d4855b57"><td class="memItemLeft" align="right" valign="top">constexpr auto&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a4feb32bd0a065a0732908716d4855b57">to_map</a> = <a class="el" href="group__group-core.html#gadc70755c1d059139297814fb3bfeb91e">to</a>&lt;<a class="el" href="structboost_1_1hana_1_1map__tag.html">map_tag</a>&gt;</td></tr>
    173. 

  173. <tr class="memdesc:a4feb32bd0a065a0732908716d4855b57"><td class="mdescLeft">&#160;</td><td class="mdescRight">Equivalent to <code>to&lt;<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps.">map_tag</a>&gt;</code>; provided for convenience.  <a href="#a4feb32bd0a065a0732908716d4855b57">More...</a><br /></td></tr>
    174. 

  174. <tr class="separator:a4feb32bd0a065a0732908716d4855b57"><td class="memSeparator" colspan="2">&#160;</td></tr>
    175. 

  175. <tr class="memitem:a0f32260f859b2510dd16235b7bc011ac"><td class="memItemLeft" align="right" valign="top">constexpr auto&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a0f32260f859b2510dd16235b7bc011ac">keys</a></td></tr>
    176. 

  176. <tr class="memdesc:a0f32260f859b2510dd16235b7bc011ac"><td class="mdescLeft">&#160;</td><td class="mdescRight">Returns a <code>Sequence</code> of the keys of the map, in unspecified order.  <a href="#a0f32260f859b2510dd16235b7bc011ac">More...</a><br /></td></tr>
    177. 

  177. <tr class="separator:a0f32260f859b2510dd16235b7bc011ac"><td class="memSeparator" colspan="2">&#160;</td></tr>
    178. 

  178. <tr class="memitem:a2e016a68e3ec6eb25868fadb7ce80132"><td class="memItemLeft" align="right" valign="top">constexpr auto&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a2e016a68e3ec6eb25868fadb7ce80132">values</a></td></tr>
    179. 

  179. <tr class="memdesc:a2e016a68e3ec6eb25868fadb7ce80132"><td class="mdescLeft">&#160;</td><td class="mdescRight">Returns a <code>Sequence</code> of the values of the map, in unspecified order.  <a href="#a2e016a68e3ec6eb25868fadb7ce80132">More...</a><br /></td></tr>
    180. 

  180. <tr class="separator:a2e016a68e3ec6eb25868fadb7ce80132"><td class="memSeparator" colspan="2">&#160;</td></tr>
    181. 

  181. <tr class="memitem:a5791e6dc0e27d8e3a113e4d94482550f"><td class="memItemLeft" align="right" valign="top">constexpr auto&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a5791e6dc0e27d8e3a113e4d94482550f">insert</a></td></tr>
    182. 

  182. <tr class="memdesc:a5791e6dc0e27d8e3a113e4d94482550f"><td class="mdescLeft">&#160;</td><td class="mdescRight">Inserts a new key/value pair in a map.  <a href="#a5791e6dc0e27d8e3a113e4d94482550f">More...</a><br /></td></tr>
    183. 

  183. <tr class="separator:a5791e6dc0e27d8e3a113e4d94482550f"><td class="memSeparator" colspan="2">&#160;</td></tr>
    184. 

  184. <tr class="memitem:af856f7bf77f69cdf1b8fd4e566eaef9b"><td class="memItemLeft" align="right" valign="top">constexpr auto&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#af856f7bf77f69cdf1b8fd4e566eaef9b">erase_key</a></td></tr>
    185. 

  185. <tr class="memdesc:af856f7bf77f69cdf1b8fd4e566eaef9b"><td class="mdescLeft">&#160;</td><td class="mdescRight">Removes a key/value pair from a map.  <a href="#af856f7bf77f69cdf1b8fd4e566eaef9b">More...</a><br /></td></tr>
    186. 

  186. <tr class="separator:af856f7bf77f69cdf1b8fd4e566eaef9b"><td class="memSeparator" colspan="2">&#160;</td></tr>
    187. 

  187. <tr class="memitem:acd511f2c01f38405bfba0b6d5b2922e8"><td class="memItemLeft" align="right" valign="top">constexpr auto&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#acd511f2c01f38405bfba0b6d5b2922e8">union_</a></td></tr>
    188. 

  188. <tr class="memdesc:acd511f2c01f38405bfba0b6d5b2922e8"><td class="mdescLeft">&#160;</td><td class="mdescRight">Returns the union of two maps.  <a href="#acd511f2c01f38405bfba0b6d5b2922e8">More...</a><br /></td></tr>
    189. 

  189. <tr class="separator:acd511f2c01f38405bfba0b6d5b2922e8"><td class="memSeparator" colspan="2">&#160;</td></tr>
    190. 

  190. <tr class="memitem:a3b3430482d4e88052e621f63a234f3eb"><td class="memItemLeft" align="right" valign="top">constexpr auto&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a3b3430482d4e88052e621f63a234f3eb">intersection</a></td></tr>
    191. 

  191. <tr class="memdesc:a3b3430482d4e88052e621f63a234f3eb"><td class="mdescLeft">&#160;</td><td class="mdescRight">Returns the intersection of two maps.  <a href="#a3b3430482d4e88052e621f63a234f3eb">More...</a><br /></td></tr>
    192. 

  192. <tr class="separator:a3b3430482d4e88052e621f63a234f3eb"><td class="memSeparator" colspan="2">&#160;</td></tr>
    193. 

  193. <tr class="memitem:a718ddfe86437adbbca1e1a5db651d139"><td class="memItemLeft" align="right" valign="top">constexpr auto&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a718ddfe86437adbbca1e1a5db651d139">difference</a></td></tr>
    194. 

  194. <tr class="memdesc:a718ddfe86437adbbca1e1a5db651d139"><td class="mdescLeft">&#160;</td><td class="mdescRight">Returns the difference of two maps.  <a href="#a718ddfe86437adbbca1e1a5db651d139">More...</a><br /></td></tr>
    195. 

  195. <tr class="separator:a718ddfe86437adbbca1e1a5db651d139"><td class="memSeparator" colspan="2">&#160;</td></tr>
    196. 

  196. <tr class="memitem:a8bcb2455eb9f7074185d8fb61a99801e"><td class="memItemLeft" align="right" valign="top">constexpr auto&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a8bcb2455eb9f7074185d8fb61a99801e">symmetric_difference</a></td></tr>
    197. 

  197. <tr class="memdesc:a8bcb2455eb9f7074185d8fb61a99801e"><td class="mdescLeft">&#160;</td><td class="mdescRight">Returns the symmetric set-theoretic difference of two maps.  <a href="#a8bcb2455eb9f7074185d8fb61a99801e">More...</a><br /></td></tr>
    198. 

  198. <tr class="separator:a8bcb2455eb9f7074185d8fb61a99801e"><td class="memSeparator" colspan="2">&#160;</td></tr>
    199. 

  199. </table><table class="memberdecls">
    200. 

  200. <tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="friends"></a>
    201. 

  201. Friends</h2></td></tr>
    202. 

  202. <tr class="memitem:a27607958295e6da8a0ba602a2db468f1"><td class="memTemplParams" colspan="2"><a id="a27607958295e6da8a0ba602a2db468f1"></a>
    203. 

  203. template&lt;typename X , typename Y &gt; </td></tr>
    204. 

  204. <tr class="memitem:a27607958295e6da8a0ba602a2db468f1"><td class="memTemplItemLeft" align="right" valign="top">constexpr auto&#160;</td><td class="memTemplItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a27607958295e6da8a0ba602a2db468f1">operator==</a> (X &amp;&amp;x, Y &amp;&amp;y)</td></tr>
    205. 

  205. <tr class="memdesc:a27607958295e6da8a0ba602a2db468f1"><td class="mdescLeft">&#160;</td><td class="mdescRight">Equivalent to <code><a class="el" href="group__group-Comparable.html#gacaf1ebea6b3ab96ac9dcb82f0e64e547" title="Returns a Logical representing whether x is equal to y.The equal function can be called in two differ...">hana::equal</a></code> <br /></td></tr>
    206. 

  206. <tr class="separator:a27607958295e6da8a0ba602a2db468f1"><td class="memSeparator" colspan="2">&#160;</td></tr>
    207. 

  207. <tr class="memitem:a0cae3af55edb3eb05bfa184bda633f7d"><td class="memTemplParams" colspan="2"><a id="a0cae3af55edb3eb05bfa184bda633f7d"></a>
    208. 

  208. template&lt;typename X , typename Y &gt; </td></tr>
    209. 

  209. <tr class="memitem:a0cae3af55edb3eb05bfa184bda633f7d"><td class="memTemplItemLeft" align="right" valign="top">constexpr auto&#160;</td><td class="memTemplItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a0cae3af55edb3eb05bfa184bda633f7d">operator!=</a> (X &amp;&amp;x, Y &amp;&amp;y)</td></tr>
    210. 

  210. <tr class="memdesc:a0cae3af55edb3eb05bfa184bda633f7d"><td class="mdescLeft">&#160;</td><td class="mdescRight">Equivalent to <code><a class="el" href="group__group-Comparable.html#gae33be2e0d5e04f19082f4b7740dfc9cd" title="Returns a Logical representing whether x is not equal to y.The not_equal function can be called in tw...">hana::not_equal</a></code> <br /></td></tr>
    211. 

  211. <tr class="separator:a0cae3af55edb3eb05bfa184bda633f7d"><td class="memSeparator" colspan="2">&#160;</td></tr>
    212. 

  212. </table><table class="memberdecls">
    213. 

  213. <tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="pub-methods"></a>
    214. 

  214. Public Member Functions</h2></td></tr>
    215. 

  215. <tr class="memitem:a1ee432be0bd10f08a637a437e311e4e2"><td class="memItemLeft" align="right" valign="top"><a id="a1ee432be0bd10f08a637a437e311e4e2"></a>
    216. 

  216. constexpr&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a1ee432be0bd10f08a637a437e311e4e2">map</a> ()=default</td></tr>
    217. 

  217. <tr class="memdesc:a1ee432be0bd10f08a637a437e311e4e2"><td class="mdescLeft">&#160;</td><td class="mdescRight">Default-construct a map. This constructor only exists when all the elements of the map are default-constructible. <br /></td></tr>
    218. 

  218. <tr class="separator:a1ee432be0bd10f08a637a437e311e4e2"><td class="memSeparator" colspan="2">&#160;</td></tr>
    219. 

  219. <tr class="memitem:a943219d1c9692938167639d8ad2525b8"><td class="memItemLeft" align="right" valign="top"><a id="a943219d1c9692938167639d8ad2525b8"></a>
    220. 

  220. constexpr&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a943219d1c9692938167639d8ad2525b8">map</a> (<a class="el" href="structboost_1_1hana_1_1map.html">map</a> const &amp;other)=default</td></tr>
    221. 

  221. <tr class="memdesc:a943219d1c9692938167639d8ad2525b8"><td class="mdescLeft">&#160;</td><td class="mdescRight">Copy-construct a map from another map. This constructor only exists when all the elements of the map are copy-constructible. <br /></td></tr>
    222. 

  222. <tr class="separator:a943219d1c9692938167639d8ad2525b8"><td class="memSeparator" colspan="2">&#160;</td></tr>
    223. 

  223. <tr class="memitem:a675bb30af155b40f72cbe8607eefbe4e"><td class="memItemLeft" align="right" valign="top"><a id="a675bb30af155b40f72cbe8607eefbe4e"></a>
    224. 

  224. constexpr&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a675bb30af155b40f72cbe8607eefbe4e">map</a> (<a class="el" href="structboost_1_1hana_1_1map.html">map</a> &amp;&amp;other)=default</td></tr>
    225. 

  225. <tr class="memdesc:a675bb30af155b40f72cbe8607eefbe4e"><td class="mdescLeft">&#160;</td><td class="mdescRight">Move-construct a map from another map. This constructor only exists when all the elements of the map are move-constructible. <br /></td></tr>
    226. 

  226. <tr class="separator:a675bb30af155b40f72cbe8607eefbe4e"><td class="memSeparator" colspan="2">&#160;</td></tr>
    227. 

  227. <tr class="memitem:a4a4f472e036abf9bcbda81e831f46e32"><td class="memTemplParams" colspan="2"><a id="a4a4f472e036abf9bcbda81e831f46e32"></a>
    228. 

  228. template&lt;typename ... P&gt; </td></tr>
    229. 

  229. <tr class="memitem:a4a4f472e036abf9bcbda81e831f46e32"><td class="memTemplItemLeft" align="right" valign="top">constexpr&#160;</td><td class="memTemplItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a4a4f472e036abf9bcbda81e831f46e32">map</a> (P &amp;&amp;...pairs)</td></tr>
    230. 

  230. <tr class="memdesc:a4a4f472e036abf9bcbda81e831f46e32"><td class="mdescLeft">&#160;</td><td class="mdescRight">Construct the map from the provided pairs. <code>P...</code> must be pairs of the same type (modulo ref and cv-qualifiers), and in the same order, as those appearing in <code>Pairs...</code>. The pairs provided to this constructor are emplaced into the map's storage using perfect forwarding. <br /></td></tr>
    231. 

  231. <tr class="separator:a4a4f472e036abf9bcbda81e831f46e32"><td class="memSeparator" colspan="2">&#160;</td></tr>
    232. 

  232. <tr class="memitem:ae18123925b628b5cfcb1adaef5c83ac7"><td class="memItemLeft" align="right" valign="top"><a id="ae18123925b628b5cfcb1adaef5c83ac7"></a>
    233. 

  233. constexpr <a class="el" href="structboost_1_1hana_1_1map.html">map</a> &amp;&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#ae18123925b628b5cfcb1adaef5c83ac7">operator=</a> (<a class="el" href="structboost_1_1hana_1_1map.html">map</a> const &amp;other)</td></tr>
    234. 

  234. <tr class="memdesc:ae18123925b628b5cfcb1adaef5c83ac7"><td class="mdescLeft">&#160;</td><td class="mdescRight">Assign a map to another map <b>with the exact same type</b>. Only exists when all the elements of the map are copy-assignable. <br /></td></tr>
    235. 

  235. <tr class="separator:ae18123925b628b5cfcb1adaef5c83ac7"><td class="memSeparator" colspan="2">&#160;</td></tr>
    236. 

  236. <tr class="memitem:a9a6635ea36edc582518d278238defa0d"><td class="memItemLeft" align="right" valign="top"><a id="a9a6635ea36edc582518d278238defa0d"></a>
    237. 

  237. constexpr <a class="el" href="structboost_1_1hana_1_1map.html">map</a> &amp;&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a9a6635ea36edc582518d278238defa0d">operator=</a> (<a class="el" href="structboost_1_1hana_1_1map.html">map</a> &amp;&amp;other)</td></tr>
    238. 

  238. <tr class="memdesc:a9a6635ea36edc582518d278238defa0d"><td class="mdescLeft">&#160;</td><td class="mdescRight">Move-assign a map to another map <b>with the exact same type</b>. Only exists when all the elements of the map are move-assignable. <br /></td></tr>
    239. 

  239. <tr class="separator:a9a6635ea36edc582518d278238defa0d"><td class="memSeparator" colspan="2">&#160;</td></tr>
    240. 

  240. <tr class="memitem:a4881a1810986e678959af8ccb58f5666"><td class="memTemplParams" colspan="2"><a id="a4881a1810986e678959af8ccb58f5666"></a>
    241. 

  241. template&lt;typename Key &gt; </td></tr>
    242. 

  242. <tr class="memitem:a4881a1810986e678959af8ccb58f5666"><td class="memTemplItemLeft" align="right" valign="top">decltype(auto) constexpr&#160;</td><td class="memTemplItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a4881a1810986e678959af8ccb58f5666">operator[]</a> (Key &amp;&amp;key)</td></tr>
    243. 

  243. <tr class="memdesc:a4881a1810986e678959af8ccb58f5666"><td class="mdescLeft">&#160;</td><td class="mdescRight">Equivalent to <code><a class="el" href="group__group-Searchable.html#ga3c1826aee6c6eb577810bb99c5c3e53d" title="Returns the value associated to the given key in a structure, or fail.Given a key and a Searchable st...">hana::at_key</a></code> <br /></td></tr>
    244. 

  244. <tr class="separator:a4881a1810986e678959af8ccb58f5666"><td class="memSeparator" colspan="2">&#160;</td></tr>
    245. 

  245. </table>
    246. 

  246. <h2 class="groupheader">Associated functions</h2>
    247. 

  247. <a id="a409d52de54cc7e55eca1a7b5dda4ce30"></a>
    248. 

  248. <h2 class="memtitle"><span class="permalink"><a href="#a409d52de54cc7e55eca1a7b5dda4ce30">&#9670;&nbsp;</a></span>make&lt; map_tag &gt;</h2>
    249. 

  249. 

  250. <div class="memitem">
    251. 

  251. <div class="memproto">
    252. 

  252. <div class="memtemplate">
    253. 

  253. template&lt;typename ... Pairs&gt; </div>
    254. 

  254. <div class="memtemplate">
    255. 

  255. template&lt;&gt; </div>
    256. 

  256. <table class="mlabels">
    257. 

  257.   <tr>
    258. 

  258.   <td class="mlabels-left">
    259. 

  259.       <table class="memname">
    260. 

  260.         <tr>
    261. 

  261.           <td class="memname">constexpr auto <a class="el" href="group__group-core.html#ga1d92480f0af1029878e773dafa3e2f60">make</a>&lt; <a class="el" href="structboost_1_1hana_1_1map__tag.html">map_tag</a> &gt;</td>
    262. 

  262.         </tr>
    263. 

  263.       </table>
    264. 

  264.   </td>
    265. 

  265.   <td class="mlabels-right">
    266. 

  266. <span class="mlabels"><span class="mlabel">related</span></span>  </td>
    267. 

  267.   </tr>
    268. 

  268. </table>
    269. 

  269. </div><div class="memdoc">
    270. 

  270. <b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&amp;&amp; ...pairs) {</div><div class="line">        <span class="keywordflow">return</span> map&lt;implementation_defined&gt;{forwarded(pairs)...};</div><div class="line">    }</div></div><!-- fragment -->
    271. 

  271. <p>Function object for creating a <code><a class="el" href="structboost_1_1hana_1_1map.html" title="Basic associative container requiring unique, Comparable and Hashable keys.">hana::map</a></code>. </p>
    272. 

  272. <p>Given zero or more <code>Product</code>s representing key/value associations, <code>make&lt;<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps.">map_tag</a>&gt;</code> returns a <code><a class="el" href="structboost_1_1hana_1_1map.html" title="Basic associative container requiring unique, Comparable and Hashable keys.">hana::map</a></code> associating these keys to these values.</p>
    273. 

  273. <p><code>make&lt;<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps.">map_tag</a>&gt;</code> requires all the keys to be unique and to have different hashes. If you need to create a map with duplicate keys or with keys whose hashes might collide, use <code>hana::to_map</code> or insert <code>(key, value)</code> pairs to an empty map successively. However, be aware that doing so will be much more compile-time intensive than using <code>make&lt;<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps.">map_tag</a>&gt;</code>, because the uniqueness of keys will have to be enforced.</p>
    274. 

  274. <h2>Example </h2>
    275. 

  275. <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="core_2make_8hpp.html">boost/hana/core/make.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>&gt;</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;string&gt;</span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"><span class="keyword">using namespace </span>std::literals;</div><div class="line"></div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() {</div><div class="line">    <a class="code" href="group__group-assertions.html#ga4796ae107d58b67e0bbccd5ae6f70101">BOOST_HANA_RUNTIME_CHECK</a>(</div><div class="line">        hana::make_map(</div><div class="line">            hana::make_pair(hana::int_c&lt;1&gt;, <span class="stringliteral">&quot;foobar&quot;</span>s),</div><div class="line">            hana::make_pair(hana::type_c&lt;void&gt;, 1234)</div><div class="line">        )</div><div class="line">        ==</div><div class="line">        hana::make&lt;hana::map_tag&gt;(</div><div class="line">            hana::make_pair(hana::int_c&lt;1&gt;, <span class="stringliteral">&quot;foobar&quot;</span>s),</div><div class="line">            hana::make_pair(hana::type_c&lt;void&gt;, 1234)</div><div class="line">        )</div><div class="line">    );</div><div class="line">}</div></div><!-- fragment --> 
    276. 

  276. </div>
    277. 

  277. </div>
    278. 

  278. <a id="ae73cf43ee56352e4c25984b0fe3c3d04"></a>
    279. 

  279. <h2 class="memtitle"><span class="permalink"><a href="#ae73cf43ee56352e4c25984b0fe3c3d04">&#9670;&nbsp;</a></span>make_map</h2>
    280. 

  280. 

  281. <div class="memitem">
    282. 

  282. <div class="memproto">
    283. 

  283. <div class="memtemplate">
    284. 

  284. template&lt;typename ... Pairs&gt; </div>
    285. 

  285. <table class="mlabels">
    286. 

  286.   <tr>
    287. 

  287.   <td class="mlabels-left">
    288. 

  288.       <table class="memname">
    289. 

  289.         <tr>
    290. 

  290.           <td class="memname">constexpr auto make_map = <a class="el" href="group__group-core.html#ga1d92480f0af1029878e773dafa3e2f60">make</a>&lt;<a class="el" href="structboost_1_1hana_1_1map__tag.html">map_tag</a>&gt;</td>
    291. 

  291.         </tr>
    292. 

  292.       </table>
    293. 

  293.   </td>
    294. 

  294.   <td class="mlabels-right">
    295. 

  295. <span class="mlabels"><span class="mlabel">related</span></span>  </td>
    296. 

  296.   </tr>
    297. 

  297. </table>
    298. 

  298. </div><div class="memdoc">
    299. 

  299. 

  300. <p>Alias to <code>make&lt;<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps.">map_tag</a>&gt;</code>; provided for convenience. </p>
    301. 

  301. <h2>Example </h2>
    302. 

  302. <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="core_2make_8hpp.html">boost/hana/core/make.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>&gt;</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;string&gt;</span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"><span class="keyword">using namespace </span>std::literals;</div><div class="line"></div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() {</div><div class="line">    <a class="code" href="group__group-assertions.html#ga4796ae107d58b67e0bbccd5ae6f70101">BOOST_HANA_RUNTIME_CHECK</a>(</div><div class="line">        hana::make_map(</div><div class="line">            hana::make_pair(hana::int_c&lt;1&gt;, <span class="stringliteral">&quot;foobar&quot;</span>s),</div><div class="line">            hana::make_pair(hana::type_c&lt;void&gt;, 1234)</div><div class="line">        )</div><div class="line">        ==</div><div class="line">        hana::make&lt;hana::map_tag&gt;(</div><div class="line">            hana::make_pair(hana::int_c&lt;1&gt;, <span class="stringliteral">&quot;foobar&quot;</span>s),</div><div class="line">            hana::make_pair(hana::type_c&lt;void&gt;, 1234)</div><div class="line">        )</div><div class="line">    );</div><div class="line">}</div></div><!-- fragment --> 
    303. 

  303. </div>
    304. 

  304. </div>
    305. 

  305. <a id="a4feb32bd0a065a0732908716d4855b57"></a>
    306. 

  306. <h2 class="memtitle"><span class="permalink"><a href="#a4feb32bd0a065a0732908716d4855b57">&#9670;&nbsp;</a></span>to_map</h2>
    307. 

  307. 

  308. <div class="memitem">
    309. 

  309. <div class="memproto">
    310. 

  310. <div class="memtemplate">
    311. 

  311. template&lt;typename ... Pairs&gt; </div>
    312. 

  312. <table class="mlabels">
    313. 

  313.   <tr>
    314. 

  314.   <td class="mlabels-left">
    315. 

  315.       <table class="memname">
    316. 

  316.         <tr>
    317. 

  317.           <td class="memname">constexpr auto to_map = <a class="el" href="group__group-core.html#gadc70755c1d059139297814fb3bfeb91e">to</a>&lt;<a class="el" href="structboost_1_1hana_1_1map__tag.html">map_tag</a>&gt;</td>
    318. 

  318.         </tr>
    319. 

  319.       </table>
    320. 

  320.   </td>
    321. 

  321.   <td class="mlabels-right">
    322. 

  322. <span class="mlabels"><span class="mlabel">related</span></span>  </td>
    323. 

  323.   </tr>
    324. 

  324. </table>
    325. 

  325. </div><div class="memdoc">
    326. 

  326. 

  327. <p>Equivalent to <code>to&lt;<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps.">map_tag</a>&gt;</code>; provided for convenience. </p>
    328. 

  328. 

  329. </div>
    330. 

  330. </div>
    331. 

  331. <a id="a0f32260f859b2510dd16235b7bc011ac"></a>
    332. 

  332. <h2 class="memtitle"><span class="permalink"><a href="#a0f32260f859b2510dd16235b7bc011ac">&#9670;&nbsp;</a></span>keys</h2>
    333. 

  333. 

  334. <div class="memitem">
    335. 

  335. <div class="memproto">
    336. 

  336. <div class="memtemplate">
    337. 

  337. template&lt;typename ... Pairs&gt; </div>
    338. 

  338. <table class="mlabels">
    339. 

  339.   <tr>
    340. 

  340.   <td class="mlabels-left">
    341. 

  341.       <table class="memname">
    342. 

  342.         <tr>
    343. 

  343.           <td class="memname">constexpr auto keys</td>
    344. 

  344.         </tr>
    345. 

  345.       </table>
    346. 

  346.   </td>
    347. 

  347.   <td class="mlabels-right">
    348. 

  348. <span class="mlabels"><span class="mlabel">related</span></span>  </td>
    349. 

  349.   </tr>
    350. 

  350. </table>
    351. 

  351. </div><div class="memdoc">
    352. 

  352. <b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&amp;&amp; <a class="code" href="structboost_1_1hana_1_1map.html#a1ee432be0bd10f08a637a437e311e4e2">map</a>) {</div><div class="line">        <span class="keywordflow">return</span> implementation_defined;</div><div class="line">    }</div></div><!-- fragment -->
    353. 

  353. <p>Returns a <code>Sequence</code> of the keys of the map, in unspecified order. </p>
    354. 

  354. <h2>Example </h2>
    355. 

  355. <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="contains_8hpp.html">boost/hana/contains.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="keys_8hpp.html">boost/hana/keys.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="permutations_8hpp.html">boost/hana/permutations.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="tuple_8hpp.html">boost/hana/tuple.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>&gt;</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;string&gt;</span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"><span class="keyword">using namespace </span>std::literals;</div><div class="line"></div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() {</div><div class="line">    <span class="keyword">auto</span> m = hana::make_map(</div><div class="line">        hana::make_pair(hana::int_c&lt;1&gt;, <span class="stringliteral">&quot;foobar&quot;</span>s),</div><div class="line">        hana::make_pair(hana::type_c&lt;void&gt;, 1234)</div><div class="line">    );</div><div class="line"></div><div class="line">    <span class="comment">// The order of the keys is unspecified.</span></div><div class="line">    <a class="code" href="group__group-assertions.html#ga2c5006540936d9f8880e3a39f4fcc035">BOOST_HANA_CONSTANT_CHECK</a>(</div><div class="line">        <a class="code" href="group__group-Struct.html#gaf8c7199742581e6e66c8397def68e2d3">hana::keys</a>(m) ^<a class="code" href="group__group-Searchable.html#ga0d9456ceda38b6ca664998e79d7c45b7">hana::in</a>^ <a class="code" href="group__group-Sequence.html#gac1e182ac088f1990edd739424d30ea07">hana::permutations</a>(hana::make_tuple(hana::int_c&lt;1&gt;, hana::type_c&lt;void&gt;))</div><div class="line">    );</div><div class="line">}</div></div><!-- fragment --> 
    356. 

  356. </div>
    357. 

  357. </div>
    358. 

  358. <a id="a2e016a68e3ec6eb25868fadb7ce80132"></a>
    359. 

  359. <h2 class="memtitle"><span class="permalink"><a href="#a2e016a68e3ec6eb25868fadb7ce80132">&#9670;&nbsp;</a></span>values</h2>
    360. 

  360. 

  361. <div class="memitem">
    362. 

  362. <div class="memproto">
    363. 

  363. <div class="memtemplate">
    364. 

  364. template&lt;typename ... Pairs&gt; </div>
    365. 

  365. <table class="mlabels">
    366. 

  366.   <tr>
    367. 

  367.   <td class="mlabels-left">
    368. 

  368.       <table class="memname">
    369. 

  369.         <tr>
    370. 

  370.           <td class="memname">constexpr auto values</td>
    371. 

  371.         </tr>
    372. 

  372.       </table>
    373. 

  373.   </td>
    374. 

  374.   <td class="mlabels-right">
    375. 

  375. <span class="mlabels"><span class="mlabel">related</span></span>  </td>
    376. 

  376.   </tr>
    377. 

  377. </table>
    378. 

  378. </div><div class="memdoc">
    379. 

  379. <b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&amp;&amp; <a class="code" href="structboost_1_1hana_1_1map.html#a1ee432be0bd10f08a637a437e311e4e2">map</a>) -&gt; decltype(<span class="keyword">auto</span>) {</div><div class="line">        <span class="keywordflow">return</span> implementation_defined;</div><div class="line">    }</div></div><!-- fragment -->
    380. 

  380. <p>Returns a <code>Sequence</code> of the values of the map, in unspecified order. </p>
    381. 

  381. <h2>Example </h2>
    382. 

  382. <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="contains_8hpp.html">boost/hana/contains.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="permutations_8hpp.html">boost/hana/permutations.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="tuple_8hpp.html">boost/hana/tuple.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>&gt;</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;string&gt;</span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"><span class="keyword">using namespace </span>std::literals;</div><div class="line"></div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() {</div><div class="line">    <span class="keyword">auto</span> m = hana::make_map(</div><div class="line">        hana::make_pair(hana::int_c&lt;1&gt;, <span class="stringliteral">&quot;foobar&quot;</span>s),</div><div class="line">        hana::make_pair(hana::type_c&lt;void&gt;, 1234)</div><div class="line">    );</div><div class="line"></div><div class="line">    <span class="comment">// The order of the values is unspecified.</span></div><div class="line">    <a class="code" href="group__group-assertions.html#ga4796ae107d58b67e0bbccd5ae6f70101">BOOST_HANA_RUNTIME_CHECK</a>(</div><div class="line">        hana::values(m) ^<a class="code" href="group__group-Searchable.html#ga0d9456ceda38b6ca664998e79d7c45b7">hana::in</a>^ <a class="code" href="group__group-Sequence.html#gac1e182ac088f1990edd739424d30ea07">hana::permutations</a>(hana::make_tuple(<span class="stringliteral">&quot;foobar&quot;</span>s, 1234))</div><div class="line">    );</div><div class="line">}</div></div><!-- fragment --> 
    383. 

  383. </div>
    384. 

  384. </div>
    385. 

  385. <a id="a5791e6dc0e27d8e3a113e4d94482550f"></a>
    386. 

  386. <h2 class="memtitle"><span class="permalink"><a href="#a5791e6dc0e27d8e3a113e4d94482550f">&#9670;&nbsp;</a></span>insert</h2>
    387. 

  387. 

  388. <div class="memitem">
    389. 

  389. <div class="memproto">
    390. 

  390. <div class="memtemplate">
    391. 

  391. template&lt;typename ... Pairs&gt; </div>
    392. 

  392. <table class="mlabels">
    393. 

  393.   <tr>
    394. 

  394.   <td class="mlabels-left">
    395. 

  395.       <table class="memname">
    396. 

  396.         <tr>
    397. 

  397.           <td class="memname">constexpr auto insert</td>
    398. 

  398.         </tr>
    399. 

  399.       </table>
    400. 

  400.   </td>
    401. 

  401.   <td class="mlabels-right">
    402. 

  402. <span class="mlabels"><span class="mlabel">related</span></span>  </td>
    403. 

  403.   </tr>
    404. 

  404. </table>
    405. 

  405. </div><div class="memdoc">
    406. 

  406. <b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&amp;&amp; <a class="code" href="structboost_1_1hana_1_1map.html#a1ee432be0bd10f08a637a437e311e4e2">map</a>, <span class="keyword">auto</span>&amp;&amp; pair) {</div><div class="line">        <span class="keywordflow">return</span> tag-dispatched;</div><div class="line">    }</div></div><!-- fragment -->
    407. 

  407. <p>Inserts a new key/value pair in a map. </p>
    408. 

  408. <p>Given a <code>(key, value)</code> pair, <code>insert</code> inserts this new pair into a map. If the map already contains this key, nothing is done and the map is returned as-is.</p>
    409. 

  409. <dl class="params"><dt>Parameters</dt><dd>
    410. 

  410.   <table class="params">
    411. 

  411.     <tr><td class="paramname">map</td><td>The map in which to insert a <code>(key,value)</code> pair.</td></tr>
    412. 

  412.     <tr><td class="paramname">pair</td><td>An arbitrary <code>Product</code> representing a <code>(key, value)</code> pair to insert in the map. The <code>key</code> must be compile-time <code>Comparable</code>.</td></tr>
    413. 

  413.   </table>
    414. 

  414.   </dd>
    415. 

  415. </dl>
    416. 

  416. <h2>Example </h2>
    417. 

  417. <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="insert_8hpp.html">boost/hana/insert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>&gt;</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;string&gt;</span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"><span class="keyword">using namespace </span>std::literals;</div><div class="line"></div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() {</div><div class="line">    <span class="keyword">auto</span> m = hana::make_map(</div><div class="line">        hana::make_pair(hana::type_c&lt;int&gt;, <span class="stringliteral">&quot;abcd&quot;</span>s),</div><div class="line">        hana::make_pair(hana::type_c&lt;void&gt;, 1234)</div><div class="line">    );</div><div class="line"></div><div class="line">    <a class="code" href="group__group-assertions.html#ga4796ae107d58b67e0bbccd5ae6f70101">BOOST_HANA_RUNTIME_CHECK</a>(</div><div class="line">        <a class="code" href="group__group-Sequence.html#gae22a1a184b1b2dd550fa4fa619bed2e9">hana::insert</a>(m, hana::make_pair(hana::type_c&lt;float&gt;, <span class="charliteral">&#39;x&#39;</span>)) ==</div><div class="line">        hana::make_map(</div><div class="line">            hana::make_pair(hana::type_c&lt;int&gt;, <span class="stringliteral">&quot;abcd&quot;</span>s),</div><div class="line">            hana::make_pair(hana::type_c&lt;void&gt;, 1234),</div><div class="line">            hana::make_pair(hana::type_c&lt;float&gt;, <span class="charliteral">&#39;x&#39;</span>)</div><div class="line">        )</div><div class="line">    );</div><div class="line"></div><div class="line">    <a class="code" href="group__group-assertions.html#ga4796ae107d58b67e0bbccd5ae6f70101">BOOST_HANA_RUNTIME_CHECK</a>(<a class="code" href="group__group-Sequence.html#gae22a1a184b1b2dd550fa4fa619bed2e9">hana::insert</a>(m, hana::make_pair(hana::type_c&lt;void&gt;, <span class="charliteral">&#39;x&#39;</span>)) == m);</div><div class="line">}</div></div><!-- fragment --> 
    418. 

  418. </div>
    419. 

  419. </div>
    420. 

  420. <a id="af856f7bf77f69cdf1b8fd4e566eaef9b"></a>
    421. 

  421. <h2 class="memtitle"><span class="permalink"><a href="#af856f7bf77f69cdf1b8fd4e566eaef9b">&#9670;&nbsp;</a></span>erase_key</h2>
    422. 

  422. 

  423. <div class="memitem">
    424. 

  424. <div class="memproto">
    425. 

  425. <div class="memtemplate">
    426. 

  426. template&lt;typename ... Pairs&gt; </div>
    427. 

  427. <table class="mlabels">
    428. 

  428.   <tr>
    429. 

  429.   <td class="mlabels-left">
    430. 

  430.       <table class="memname">
    431. 

  431.         <tr>
    432. 

  432.           <td class="memname">constexpr auto erase_key</td>
    433. 

  433.         </tr>
    434. 

  434.       </table>
    435. 

  435.   </td>
    436. 

  436.   <td class="mlabels-right">
    437. 

  437. <span class="mlabels"><span class="mlabel">related</span></span>  </td>
    438. 

  438.   </tr>
    439. 

  439. </table>
    440. 

  440. </div><div class="memdoc">
    441. 

  441. <b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&amp;&amp; <a class="code" href="structboost_1_1hana_1_1map.html#a1ee432be0bd10f08a637a437e311e4e2">map</a>, <span class="keyword">auto</span>&amp;&amp; key) {</div><div class="line">        <span class="keywordflow">return</span> tag-dispatched;</div><div class="line">    }</div></div><!-- fragment -->
    442. 

  442. <p>Removes a key/value pair from a map. </p>
    443. 

  443. <p>Returns a new <code><a class="el" href="structboost_1_1hana_1_1map.html" title="Basic associative container requiring unique, Comparable and Hashable keys.">hana::map</a></code> containing all the elements of the original, except for the <code>(key, value)</code> pair whose <code>key</code> compares <code>equal</code> to the given key. If the map does not contain such an element, a new map equal to the original is returned.</p>
    444. 

  444. <dl class="params"><dt>Parameters</dt><dd>
    445. 

  445.   <table class="params">
    446. 

  446.     <tr><td class="paramname">map</td><td>The map in which to erase a <code>key</code>.</td></tr>
    447. 

  447.     <tr><td class="paramname">key</td><td>A key to remove from the map. It must be compile-time <code>Comparable</code>.</td></tr>
    448. 

  448.   </table>
    449. 

  449.   </dd>
    450. 

  450. </dl>
    451. 

  451. <h2>Example </h2>
    452. 

  452. <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="erase__key_8hpp.html">boost/hana/erase_key.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="string_8hpp.html">boost/hana/string.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>&gt;</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;string&gt;</span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"><span class="keyword">using namespace </span>std::literals;</div><div class="line"></div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() {</div><div class="line">    <span class="keyword">auto</span> m = hana::make_map(</div><div class="line">        hana::make_pair(hana::type_c&lt;int&gt;, <span class="stringliteral">&quot;abcd&quot;</span>s),</div><div class="line">        hana::make_pair(hana::type_c&lt;void&gt;, 1234),</div><div class="line">        hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;foobar!&quot;</span>), hana::type_c&lt;char&gt;)</div><div class="line">    );</div><div class="line"></div><div class="line">    <a class="code" href="group__group-assertions.html#ga4796ae107d58b67e0bbccd5ae6f70101">BOOST_HANA_RUNTIME_CHECK</a>(</div><div class="line">        hana::erase_key(m, BOOST_HANA_STRING(<span class="stringliteral">&quot;foobar!&quot;</span>)) ==</div><div class="line">        hana::make_map(</div><div class="line">            hana::make_pair(hana::type_c&lt;int&gt;, <span class="stringliteral">&quot;abcd&quot;</span>s),</div><div class="line">            hana::make_pair(hana::type_c&lt;void&gt;, 1234)</div><div class="line">        )</div><div class="line">    );</div><div class="line"></div><div class="line">    <a class="code" href="group__group-assertions.html#ga4796ae107d58b67e0bbccd5ae6f70101">BOOST_HANA_RUNTIME_CHECK</a>(hana::erase_key(m, hana::type_c&lt;char&gt;) == m);</div><div class="line">}</div></div><!-- fragment --> 
    453. 

  453. </div>
    454. 

  454. </div>
    455. 

  455. <a id="acd511f2c01f38405bfba0b6d5b2922e8"></a>
    456. 

  456. <h2 class="memtitle"><span class="permalink"><a href="#acd511f2c01f38405bfba0b6d5b2922e8">&#9670;&nbsp;</a></span>union_</h2>
    457. 

  457. 

  458. <div class="memitem">
    459. 

  459. <div class="memproto">
    460. 

  460. <div class="memtemplate">
    461. 

  461. template&lt;typename ... Pairs&gt; </div>
    462. 

  462. <table class="mlabels">
    463. 

  463.   <tr>
    464. 

  464.   <td class="mlabels-left">
    465. 

  465.       <table class="memname">
    466. 

  466.         <tr>
    467. 

  467.           <td class="memname">constexpr auto union_</td>
    468. 

  468.         </tr>
    469. 

  469.       </table>
    470. 

  470.   </td>
    471. 

  471.   <td class="mlabels-right">
    472. 

  472. <span class="mlabels"><span class="mlabel">related</span></span>  </td>
    473. 

  473.   </tr>
    474. 

  474. </table>
    475. 

  475. </div><div class="memdoc">
    476. 

  476. <b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&amp;&amp; xs, <span class="keyword">auto</span>&amp;&amp; ys) {</div><div class="line">        <span class="keywordflow">return</span> tag-dispatched;</div><div class="line">    }</div></div><!-- fragment -->
    477. 

  477. <p>Returns the union of two maps. </p>
    478. 

  478. <p>Given two maps <code>xs</code> and <code>ys</code>, <code>hana::union_(xs, ys)</code> is a new map containing all the elements of <code>xs</code> and all the elements of <code>ys</code>, without duplicates. If both <code>xs</code> and <code>ys</code> contain an element with the same <code>key</code>, the one in <code>ys</code> is taken. Functionally, <code>hana::union_(xs, ys)</code> is equivalent to </p><div class="fragment"><div class="line"><a class="code" href="group__group-Foldable.html#ga38c6b3f6b1cbadb9b8432a05ff16b7d2">hana::fold_left</a>(xs, ys, <a class="code" href="group__group-Sequence.html#gae22a1a184b1b2dd550fa4fa619bed2e9">hana::insert</a>)</div></div><!-- fragment --><dl class="params"><dt>Parameters</dt><dd>
    479. 

  479.   <table class="params">
    480. 

  480.     <tr><td class="paramname">xs,ys</td><td>The two maps to compute the union of.</td></tr>
    481. 

  481.   </table>
    482. 

  482.   </dd>
    483. 

  483. </dl>
    484. 

  484. <h2>Example </h2>
    485. 

  485. <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="equal_8hpp.html">boost/hana/equal.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="string_8hpp.html">boost/hana/string.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="union_8hpp.html">boost/hana/union.hpp</a>&gt;</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;string&gt;</span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"><span class="keyword">using namespace </span>hana::literals;</div><div class="line"></div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keyword">auto</span> m1 = hana::make_map(</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key1&quot;</span>), hana::type_c&lt;std::string&gt;),</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key2&quot;</span>), hana::type_c&lt;std::string&gt;)</div><div class="line">);</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keyword">auto</span> m2 = hana::make_map(</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key3&quot;</span>), hana::type_c&lt;std::string&gt;),</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key4&quot;</span>), hana::type_c&lt;std::string&gt;),</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key5&quot;</span>), hana::type_c&lt;std::string&gt;)</div><div class="line">);</div><div class="line"></div><div class="line"><a class="code" href="group__group-assertions.html#ga2c5006540936d9f8880e3a39f4fcc035">BOOST_HANA_CONSTANT_CHECK</a>(hana::union_(m1, m2) == hana::make_map(</div><div class="line">       hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key1&quot;</span>), hana::type_c&lt;std::string&gt;),</div><div class="line">       hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key2&quot;</span>), hana::type_c&lt;std::string&gt;),</div><div class="line">       hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key3&quot;</span>), hana::type_c&lt;std::string&gt;),</div><div class="line">       hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key4&quot;</span>), hana::type_c&lt;std::string&gt;),</div><div class="line">       hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key5&quot;</span>), hana::type_c&lt;std::string&gt;)</div><div class="line">));</div><div class="line"></div><div class="line">constexpr <span class="keyword">auto</span> m3 = hana::make_map(</div><div class="line">    hana::make_pair(hana::type_c&lt;int&gt;, hana::int_c&lt;1&gt;),</div><div class="line">    hana::make_pair(hana::type_c&lt;bool&gt;, hana::bool_c&lt;true&gt;)</div><div class="line">);</div><div class="line"></div><div class="line">constexpr <span class="keyword">auto</span> m4 = hana::make_map(</div><div class="line">       hana::make_pair(hana::type_c&lt;char&gt;, hana::char_c&lt;&#39;c&#39;&gt;),</div><div class="line">       hana::make_pair(hana::type_c&lt;bool&gt;, hana::bool_c&lt;false&gt;)</div><div class="line">);</div><div class="line"></div><div class="line"><a class="code" href="group__group-assertions.html#ga2c5006540936d9f8880e3a39f4fcc035">BOOST_HANA_CONSTANT_CHECK</a>(hana::union_(m3, m4) == hana::make_map(</div><div class="line">       hana::make_pair(hana::type_c&lt;int&gt;, hana::int_c&lt;1&gt;),</div><div class="line">       hana::make_pair(hana::type_c&lt;bool&gt;, hana::bool_c&lt;false&gt;),</div><div class="line">       hana::make_pair(hana::type_c&lt;char&gt;, hana::char_c&lt;&#39;c&#39;&gt;)</div><div class="line">));</div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() { }</div></div><!-- fragment --> 
    486. 

  486. </div>
    487. 

  487. </div>
    488. 

  488. <a id="a3b3430482d4e88052e621f63a234f3eb"></a>
    489. 

  489. <h2 class="memtitle"><span class="permalink"><a href="#a3b3430482d4e88052e621f63a234f3eb">&#9670;&nbsp;</a></span>intersection</h2>
    490. 

  490. 

  491. <div class="memitem">
    492. 

  492. <div class="memproto">
    493. 

  493. <div class="memtemplate">
    494. 

  494. template&lt;typename ... Pairs&gt; </div>
    495. 

  495. <table class="mlabels">
    496. 

  496.   <tr>
    497. 

  497.   <td class="mlabels-left">
    498. 

  498.       <table class="memname">
    499. 

  499.         <tr>
    500. 

  500.           <td class="memname">constexpr auto intersection</td>
    501. 

  501.         </tr>
    502. 

  502.       </table>
    503. 

  503.   </td>
    504. 

  504.   <td class="mlabels-right">
    505. 

  505. <span class="mlabels"><span class="mlabel">related</span></span>  </td>
    506. 

  506.   </tr>
    507. 

  507. </table>
    508. 

  508. </div><div class="memdoc">
    509. 

  509. <b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&amp;&amp; xs, <span class="keyword">auto</span>&amp;&amp; ys) {</div><div class="line">        <span class="keywordflow">return</span> tag-dispatched;</div><div class="line">    }</div></div><!-- fragment -->
    510. 

  510. <p>Returns the intersection of two maps. </p>
    511. 

  511. <p>Given two maps <code>xs</code> and <code>ys</code>, <code>intersection(xs, ys)</code> is a new map containing exactly those (key, value) pairs from xs, for which key is present in <code>ys</code>. In other words, the following holds for any object <code>pair(k, v)</code>: </p><div class="fragment"><div class="line">pair(k, v) ^<a class="code" href="group__group-Searchable.html#ga0d9456ceda38b6ca664998e79d7c45b7">in</a>^ <a class="code" href="structboost_1_1hana_1_1map.html#a3b3430482d4e88052e621f63a234f3eb">intersection</a>(xs, ys) <span class="keywordflow">if</span> and only <span class="keywordflow">if</span> (k, v) ^<a class="code" href="group__group-Searchable.html#ga0d9456ceda38b6ca664998e79d7c45b7">in</a>^ xs &amp;&amp; k ^<a class="code" href="group__group-Searchable.html#ga0d9456ceda38b6ca664998e79d7c45b7">in</a>^ <a class="code" href="structboost_1_1hana_1_1map.html#a0f32260f859b2510dd16235b7bc011ac">keys</a>(ys)</div></div><!-- fragment --><dl class="section note"><dt>Note</dt><dd>This function is not commutative, i.e. <code>intersection(xs, ys)</code> is not necessarily the same as <code>intersection(ys, xs)</code>. Indeed, the set of keys in <code>intersection(xs, ys)</code> is always the same as the set of keys in <code>intersection(ys, xs)</code>, but the value associated to each key may be different. <code>intersection(xs, ys)</code> contains values present in <code>xs</code>, and <code>intersection(ys, xs)</code> contains values present in <code>ys</code>.</dd></dl>
    512. 

  512. <dl class="params"><dt>Parameters</dt><dd>
    513. 

  513.   <table class="params">
    514. 

  514.     <tr><td class="paramname">xs,ys</td><td>Two maps to intersect.</td></tr>
    515. 

  515.   </table>
    516. 

  516.   </dd>
    517. 

  517. </dl>
    518. 

  518. <h2>Example </h2>
    519. 

  519. <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="equal_8hpp.html">boost/hana/equal.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="intersection_8hpp.html">boost/hana/intersection.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="string_8hpp.html">boost/hana/string.hpp</a>&gt;</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;string&gt;</span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"><span class="keyword">using namespace </span>hana::literals;</div><div class="line"></div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keyword">auto</span> m1 = hana::make_map(</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key1&quot;</span>), hana::type_c&lt;std::string&gt;),</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key2&quot;</span>), hana::type_c&lt;std::string&gt;)</div><div class="line">);</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keyword">auto</span> m2 = hana::make_map(</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key3&quot;</span>), hana::type_c&lt;std::string&gt;),</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key4&quot;</span>), hana::type_c&lt;std::string&gt;),</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key5&quot;</span>), hana::type_c&lt;std::string&gt;)</div><div class="line">);</div><div class="line"></div><div class="line"><a class="code" href="group__group-assertions.html#ga2c5006540936d9f8880e3a39f4fcc035">BOOST_HANA_CONSTANT_CHECK</a>(hana::intersection(m1, m2) == hana::make_map());</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keyword">auto</span> m3 = hana::make_map(</div><div class="line">    hana::make_pair(hana::type_c&lt;int&gt;, hana::int_c&lt;1&gt;),</div><div class="line">    hana::make_pair(hana::type_c&lt;bool&gt;, hana::bool_c&lt;true&gt;),</div><div class="line">    hana::make_pair(hana::type_c&lt;std::string&gt;, BOOST_HANA_STRING(<span class="stringliteral">&quot;hana&quot;</span>)),</div><div class="line">    hana::make_pair(hana::type_c&lt;float&gt;, hana::int_c&lt;100&gt;)</div><div class="line">);</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keyword">auto</span> m4 = hana::make_map(</div><div class="line">       hana::make_pair(hana::type_c&lt;char&gt;, hana::char_c&lt;&#39;c&#39;&gt;),</div><div class="line">       hana::make_pair(hana::type_c&lt;bool&gt;, hana::bool_c&lt;false&gt;),</div><div class="line">       hana::make_pair(hana::type_c&lt;std::string&gt;, BOOST_HANA_STRING(<span class="stringliteral">&quot;boost&quot;</span>))</div><div class="line">);</div><div class="line"></div><div class="line"><a class="code" href="group__group-assertions.html#ga2c5006540936d9f8880e3a39f4fcc035">BOOST_HANA_CONSTANT_CHECK</a>(hana::intersection(m3, m4) == hana::make_map(</div><div class="line">    hana::make_pair(hana::type_c&lt;bool&gt;, hana::bool_c&lt;true&gt;),</div><div class="line">    hana::make_pair(hana::type_c&lt;std::string&gt;, BOOST_HANA_STRING(<span class="stringliteral">&quot;hana&quot;</span>))</div><div class="line">));</div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() { }</div></div><!-- fragment --> 
    520. 

  520. </div>
    521. 

  521. </div>
    522. 

  522. <a id="a718ddfe86437adbbca1e1a5db651d139"></a>
    523. 

  523. <h2 class="memtitle"><span class="permalink"><a href="#a718ddfe86437adbbca1e1a5db651d139">&#9670;&nbsp;</a></span>difference</h2>
    524. 

  524. 

  525. <div class="memitem">
    526. 

  526. <div class="memproto">
    527. 

  527. <div class="memtemplate">
    528. 

  528. template&lt;typename ... Pairs&gt; </div>
    529. 

  529. <table class="mlabels">
    530. 

  530.   <tr>
    531. 

  531.   <td class="mlabels-left">
    532. 

  532.       <table class="memname">
    533. 

  533.         <tr>
    534. 

  534.           <td class="memname">constexpr auto difference</td>
    535. 

  535.         </tr>
    536. 

  536.       </table>
    537. 

  537.   </td>
    538. 

  538.   <td class="mlabels-right">
    539. 

  539. <span class="mlabels"><span class="mlabel">related</span></span>  </td>
    540. 

  540.   </tr>
    541. 

  541. </table>
    542. 

  542. </div><div class="memdoc">
    543. 

  543. <b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&amp;&amp; xs, <span class="keyword">auto</span>&amp;&amp; ys) {</div><div class="line">        <span class="keywordflow">return</span> tag-dispatched;</div><div class="line">    }</div></div><!-- fragment -->
    544. 

  544. <p>Returns the difference of two maps. </p>
    545. 

  545. <p>Given two maps <code>xs</code> and <code>ys</code>, <code>difference(xs, ys)</code> is a new map containing exactly those (key, value) pairs from xs, for which key is not present in <code>keys(ys)</code>. In other words, the following holds for any object <code>pair(k, v)</code>: </p><div class="fragment"><div class="line">pair(k, v) ^<a class="code" href="group__group-Searchable.html#ga0d9456ceda38b6ca664998e79d7c45b7">in</a>^ <a class="code" href="structboost_1_1hana_1_1map.html#a718ddfe86437adbbca1e1a5db651d139">difference</a>(xs, ys) <span class="keywordflow">if</span> and only <span class="keywordflow">if</span> (k, v) ^<a class="code" href="group__group-Searchable.html#ga0d9456ceda38b6ca664998e79d7c45b7">in</a>^ xs &amp;&amp; k ^not <a class="code" href="group__group-Searchable.html#ga0d9456ceda38b6ca664998e79d7c45b7">in</a>^ <a class="code" href="structboost_1_1hana_1_1map.html#a0f32260f859b2510dd16235b7bc011ac">keys</a>(ys)</div></div><!-- fragment --><dl class="section note"><dt>Note</dt><dd>This function is not commutative, i.e. <code>difference(xs, ys)</code> is not necessarily the same as <code>difference(ys, xs)</code>. Indeed, consider the case where <code>xs</code> is empty and <code>ys</code> isn't. In that case, <code>difference(xs, ys)</code> is empty, but <code>difference(ys, xs)</code> is equal to <code>ys</code>. For symmetric version of this operation, see <code>symmetric_difference</code>.</dd></dl>
    546. 

  546. <dl class="params"><dt>Parameters</dt><dd>
    547. 

  547.   <table class="params">
    548. 

  548.     <tr><td class="paramname">xs,ys</td><td>Two maps to compute the difference of.</td></tr>
    549. 

  549.   </table>
    550. 

  550.   </dd>
    551. 

  551. </dl>
    552. 

  552. <h2>Example </h2>
    553. 

  553. <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="equal_8hpp.html">boost/hana/equal.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="intersection_8hpp.html">boost/hana/intersection.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="string_8hpp.html">boost/hana/string.hpp</a>&gt;</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;string&gt;</span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"><span class="keyword">using namespace </span>hana::literals;</div><div class="line"></div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keyword">auto</span> m1 = hana::make_map(</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key1&quot;</span>), hana::type_c&lt;std::string&gt;),</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key2&quot;</span>), hana::type_c&lt;std::string&gt;)</div><div class="line">);</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keyword">auto</span> m2 = hana::make_map(</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key3&quot;</span>), hana::type_c&lt;std::string&gt;),</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key4&quot;</span>), hana::type_c&lt;std::string&gt;),</div><div class="line">    hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">&quot;key5&quot;</span>), hana::type_c&lt;std::string&gt;)</div><div class="line">);</div><div class="line"></div><div class="line"><a class="code" href="group__group-assertions.html#ga2c5006540936d9f8880e3a39f4fcc035">BOOST_HANA_CONSTANT_CHECK</a>(hana::intersection(m1, m2) == hana::make_map());</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keyword">auto</span> m3 = hana::make_map(</div><div class="line">    hana::make_pair(hana::type_c&lt;int&gt;, hana::int_c&lt;1&gt;),</div><div class="line">    hana::make_pair(hana::type_c&lt;bool&gt;, hana::bool_c&lt;true&gt;),</div><div class="line">    hana::make_pair(hana::type_c&lt;std::string&gt;, BOOST_HANA_STRING(<span class="stringliteral">&quot;hana&quot;</span>)),</div><div class="line">    hana::make_pair(hana::type_c&lt;float&gt;, hana::int_c&lt;100&gt;)</div><div class="line">);</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keyword">auto</span> m4 = hana::make_map(</div><div class="line">       hana::make_pair(hana::type_c&lt;char&gt;, hana::char_c&lt;&#39;c&#39;&gt;),</div><div class="line">       hana::make_pair(hana::type_c&lt;bool&gt;, hana::bool_c&lt;false&gt;),</div><div class="line">       hana::make_pair(hana::type_c&lt;std::string&gt;, BOOST_HANA_STRING(<span class="stringliteral">&quot;boost&quot;</span>))</div><div class="line">);</div><div class="line"></div><div class="line"><a class="code" href="group__group-assertions.html#ga2c5006540936d9f8880e3a39f4fcc035">BOOST_HANA_CONSTANT_CHECK</a>(hana::intersection(m3, m4) == hana::make_map(</div><div class="line">    hana::make_pair(hana::type_c&lt;bool&gt;, hana::bool_c&lt;true&gt;),</div><div class="line">    hana::make_pair(hana::type_c&lt;std::string&gt;, BOOST_HANA_STRING(<span class="stringliteral">&quot;hana&quot;</span>))</div><div class="line">));</div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() { }</div></div><!-- fragment --> 
    554. 

  554. </div>
    555. 

  555. </div>
    556. 

  556. <a id="a8bcb2455eb9f7074185d8fb61a99801e"></a>
    557. 

  557. <h2 class="memtitle"><span class="permalink"><a href="#a8bcb2455eb9f7074185d8fb61a99801e">&#9670;&nbsp;</a></span>symmetric_difference</h2>
    558. 

  558. 

  559. <div class="memitem">
    560. 

  560. <div class="memproto">
    561. 

  561. <div class="memtemplate">
    562. 

  562. template&lt;typename ... Pairs&gt; </div>
    563. 

  563. <table class="mlabels">
    564. 

  564.   <tr>
    565. 

  565.   <td class="mlabels-left">
    566. 

  566.       <table class="memname">
    567. 

  567.         <tr>
    568. 

  568.           <td class="memname">constexpr auto symmetric_difference</td>
    569. 

  569.         </tr>
    570. 

  570.       </table>
    571. 

  571.   </td>
    572. 

  572.   <td class="mlabels-right">
    573. 

  573. <span class="mlabels"><span class="mlabel">related</span></span>  </td>
    574. 

  574.   </tr>
    575. 

  575. </table>
    576. 

  576. </div><div class="memdoc">
    577. 

  577. <b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&amp;&amp; xs, <span class="keyword">auto</span>&amp;&amp; ys) {</div><div class="line">        <span class="keywordflow">return</span> tag-dispatched;</div><div class="line">    }</div></div><!-- fragment -->
    578. 

  578. <p>Returns the symmetric set-theoretic difference of two maps. </p>
    579. 

  579. <p>Given two sets <code>xs</code> and <code>ys</code>, <code>symmetric_difference(xs, ys)</code> is a new map containing all the elements of <code>xs</code> whose keys are not contained in <code>keys(ys)</code>, and all the elements of <code>ys</code> whose keys are not contained in <code>keys(xs)</code>. The symmetric difference of two maps satisfies the following: </p><div class="fragment"><div class="line"><a class="code" href="structboost_1_1hana_1_1map.html#a8bcb2455eb9f7074185d8fb61a99801e">symmetric_difference</a>(xs, ys) == <a class="code" href="structboost_1_1hana_1_1map.html#acd511f2c01f38405bfba0b6d5b2922e8">union_</a>(<a class="code" href="structboost_1_1hana_1_1map.html#a718ddfe86437adbbca1e1a5db651d139">difference</a>(xs, ys), <a class="code" href="structboost_1_1hana_1_1map.html#a718ddfe86437adbbca1e1a5db651d139">difference</a>(ys, xs))</div></div><!-- fragment --><dl class="params"><dt>Parameters</dt><dd>
    580. 

  580.   <table class="params">
    581. 

  581.     <tr><td class="paramname">xs,ys</td><td>Two maps to compute the symmetric difference of.</td></tr>
    582. 

  582.   </table>
    583. 

  583.   </dd>
    584. 

  584. </dl>
    585. 

  585. <h2>Example </h2>
    586. 

  586. <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="symmetric__difference_8hpp.html">boost/hana/symmetric_difference.hpp</a>&gt;</span></div><div class="line"></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"></div><div class="line"></div><div class="line">constexpr <span class="keyword">auto</span> m1 = hana::make_map(</div><div class="line">    hana::make_pair(hana::type_c&lt;int&gt;, 1),</div><div class="line">    hana::make_pair(hana::type_c&lt;bool&gt;, hana::true_c)</div><div class="line">);</div><div class="line"></div><div class="line">constexpr <span class="keyword">auto</span> m2 = hana::make_map(</div><div class="line">    hana::make_pair(hana::type_c&lt;float&gt;, 1.0),</div><div class="line">    hana::make_pair(hana::type_c&lt;long long&gt;, 2LL),</div><div class="line">    hana::make_pair(hana::type_c&lt;int&gt;, 3)</div><div class="line">);</div><div class="line"></div><div class="line">constexpr <span class="keyword">auto</span> result_m = hana::make_map(</div><div class="line">    hana::make_pair(hana::type_c&lt;bool&gt;, hana::true_c),</div><div class="line">    hana::make_pair(hana::type_c&lt;float&gt;, 1.0),</div><div class="line">    hana::make_pair(hana::type_c&lt;long long&gt;, 2LL)</div><div class="line">);</div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() {</div><div class="line">    <a class="code" href="group__group-assertions.html#ga4796ae107d58b67e0bbccd5ae6f70101">BOOST_HANA_RUNTIME_CHECK</a>(</div><div class="line">            hana::symmetric_difference(m1, m2) == result_m</div><div class="line">    );</div><div class="line">}</div></div><!-- fragment --> 
    587. 

  587. </div>
    588. 

  588. </div>
    589. 

  589. </div><!-- contents -->
    590. 

  590. </div><!-- doc-content -->
    591. 

  591. <!--
    592. 

  592. Copyright Louis Dionne 2013-2017
    593. 

  593. Distributed under the Boost Software License, Version 1.0.
    594. 

  594. (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
    595. 

  595. -->
    596. 

  596. <!-- boost-no-inspect -->
    597. 

  597. <!-- HTML footer for doxygen 1.8.9.1-->
    598. 

  598. <!-- start footer part -->
    599. 

  599. <div id="nav-path" class="navpath"><!-- id is needed for treeview function! -->
    600. 

  600.   <ul>
    601. 

  601.     <li class="navelem"><b>boost</b></li><li class="navelem"><a class="el" href="namespaceboost_1_1hana.html">hana</a></li><li class="navelem"><a class="el" href="structboost_1_1hana_1_1map.html">map</a></li>
    602. 

  602.   </ul>
    603. 

  603. </div>
    604. 

  604. </body>
    605. 

  605. </html>
    606.