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<a href="#related">Synopsis of associated functions</a> |
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<div class="title">boost::hana::map< Pairs > Struct Template Reference<div class="ingroups"><a class="el" href="group__group-datatypes.html">Data types</a></div></div> </div>
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<a name="details" id="details"></a><h2 class="groupheader">Description</h2>
<div class="textblock"><h3>template<typename... Pairs><br />
struct boost::hana::map< Pairs ></h3>
<p>Basic associative container requiring unique, <code>Comparable</code> and <code>Hashable</code> keys. </p>
<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>
<p>Note that 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:</p><ul>
<li>the presence of additional constructors</li>
<li>the presence of additional assignment operators</li>
<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><Pairs...></code> is, or is not, a dependent type</li>
</ul>
<p>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><Pairs...></code> is basically equivalent to </p><div class="fragment"><div class="line">decltype(hana::make_pair(std::declval<Pairs>()...))</div></div><!-- fragment --><p> which is not something that can be pattern-matched on during template argument deduction, for example.</p>
<h2>Modeled concepts </h2>
<ol type="1">
<li><code>Comparable</code><br />
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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>></span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <string></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#ga29b2b21ffa5513e5b706c50ffee980af">BOOST_HANA_RUNTIME_CHECK</a>(</div><div class="line"> hana::make_map(</div><div class="line"> hana::make_pair(hana::char_c<'a'>, <span class="stringliteral">"foobar"</span>s),</div><div class="line"> hana::make_pair(hana::type_c<int&&>, <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<int&&>, (<span class="keywordtype">void</span>*)0),</div><div class="line"> hana::make_pair(hana::char_c<'a'>, <span class="stringliteral">"foobar"</span>s)</div><div class="line"> )</div><div class="line"> );</div><div class="line">}</div></div><!-- fragment --></li>
<li><code>Searchable</code><br />
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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="at__key_8hpp.html">boost/hana/at_key.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="equal_8hpp.html">boost/hana/equal.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="find_8hpp.html">boost/hana/find.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="optional_8hpp.html">boost/hana/optional.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>></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<int>, <span class="charliteral">'i'</span>),</div><div class="line"> hana::make_pair(hana::type_c<float>, <span class="charliteral">'f'</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<int>) == hana::just(<span class="charliteral">'i'</span>), <span class="stringliteral">""</span>);</div><div class="line">static_assert(<a class="code" href="group__group-Searchable.html#ga6b6cdd69942b0fe3bf5254247f9c861e">hana::find</a>(m, hana::type_c<float>) == hana::just(<span class="charliteral">'f'</span>), <span class="stringliteral">""</span>);</div><div class="line"><a class="code" href="group__group-assertions.html#ga4bf9e0c46c44e21fbe5c5fbb3ace8356">BOOST_HANA_CONSTANT_CHECK</a>(<a class="code" href="group__group-Searchable.html#ga6b6cdd69942b0fe3bf5254247f9c861e">hana::find</a>(m, hana::type_c<void>) == hana::nothing);</div><div class="line"><a class="code" href="group__group-assertions.html#ga4bf9e0c46c44e21fbe5c5fbb3ace8356">BOOST_HANA_CONSTANT_CHECK</a>(<a class="code" href="group__group-Searchable.html#ga6b6cdd69942b0fe3bf5254247f9c861e">hana::find</a>(m, hana::int_c<3>) == 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<int>] == <span class="charliteral">'i'</span>, <span class="stringliteral">""</span>);</div><div class="line">static_assert(m[hana::type_c<float>] == <span class="charliteral">'f'</span>, <span class="stringliteral">""</span>);</div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() { }</div></div><!-- fragment --></li>
<li><code>Foldable</code><br />
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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="first_8hpp.html">boost/hana/first.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="fold__left_8hpp.html">boost/hana/fold_left.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="insert_8hpp.html">boost/hana/insert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="second_8hpp.html">boost/hana/second.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>></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<int>, hana::int_c<1>),</div><div class="line"> hana::make_pair(hana::type_c<float>, hana::int_c<2>),</div><div class="line"> hana::make_pair(hana::int_c<3>, hana::type_c<void>)</div><div class="line"> );</div><div class="line"></div><div class="line"> <a class="code" href="group__group-assertions.html#ga4bf9e0c46c44e21fbe5c5fbb3ace8356">BOOST_HANA_CONSTANT_CHECK</a>(invert(m) ==</div><div class="line"> hana::make_map(</div><div class="line"> hana::make_pair(hana::int_c<1>, hana::type_c<int>),</div><div class="line"> hana::make_pair(hana::int_c<2>, hana::type_c<float>),</div><div class="line"> hana::make_pair(hana::type_c<void>, hana::int_c<3>)</div><div class="line"> )</div><div class="line"> );</div><div class="line">}</div></div><!-- fragment --></li>
</ol>
<h2>Conversion from any <code>Foldable</code> </h2>
<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><<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps. ">hana::map_tag</a>></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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="core_2to_8hpp.html">boost/hana/core/to.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="tuple_8hpp.html">boost/hana/tuple.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>></span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <string></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<int>, <span class="stringliteral">"abcd"</span>s),</div><div class="line"> hana::make_pair(hana::type_c<void>, 1234),</div><div class="line"> hana::make_pair(hana::type_c<int>, <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#ga29b2b21ffa5513e5b706c50ffee980af">BOOST_HANA_RUNTIME_CHECK</a>(</div><div class="line"> hana::to<hana::map_tag>(xs) == hana::make_map(</div><div class="line"> hana::make_pair(hana::type_c<int>, <span class="stringliteral">"abcd"</span>s),</div><div class="line"> hana::make_pair(hana::type_c<void>, 1234)</div><div class="line"> )</div><div class="line"> );</div><div class="line">}</div></div><!-- fragment --><h2>Example </h2>
<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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="at__key_8hpp.html">boost/hana/at_key.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="contains_8hpp.html">boost/hana/contains.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="string_8hpp.html">boost/hana/string.hpp</a>></span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <functional></span></div><div class="line"><span class="preprocessor">#include <string></span></div><div class="line"><span class="preprocessor">#include <vector></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> <<span class="keyword">typename</span> ...Events></div><div class="line"><span class="keyword">struct </span>event_system {</div><div class="line"> <span class="keyword">using</span> Callback = std::function<void()>;</div><div class="line"> hana::map<hana::pair<Events, std::vector<Callback>>...> map_;</div><div class="line"></div><div class="line"> <span class="keyword">template</span> <<span class="keyword">typename</span> Event, <span class="keyword">typename</span> F></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">"trying to add a handler to an unknown event"</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> <<span class="keyword">typename</span> Event></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">"trying to trigger an unknown event"</span>);</div><div class="line"></div><div class="line"> <span class="keywordflow">for</span> (<span class="keyword">auto</span>& handler : this->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> <<span class="keyword">typename</span> ...Events></div><div class="line">event_system<Events...> 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">"foo"</span>),</div><div class="line"> BOOST_HANA_STRING(<span class="stringliteral">"bar"</span>),</div><div class="line"> BOOST_HANA_STRING(<span class="stringliteral">"baz"</span>)</div><div class="line"> );</div><div class="line"></div><div class="line"> std::vector<std::string> triggered_events;</div><div class="line"> events.on(BOOST_HANA_STRING(<span class="stringliteral">"foo"</span>), [&] {</div><div class="line"> triggered_events.push_back(<span class="stringliteral">"foo:1"</span>);</div><div class="line"> });</div><div class="line"> events.on(BOOST_HANA_STRING(<span class="stringliteral">"foo"</span>), [&] {</div><div class="line"> triggered_events.push_back(<span class="stringliteral">"foo:2"</span>);</div><div class="line"> });</div><div class="line"> events.on(BOOST_HANA_STRING(<span class="stringliteral">"bar"</span>), [&] {</div><div class="line"> triggered_events.push_back(<span class="stringliteral">"bar:1"</span>);</div><div class="line"> });</div><div class="line"> events.on(BOOST_HANA_STRING(<span class="stringliteral">"baz"</span>), [&] {</div><div class="line"> triggered_events.push_back(<span class="stringliteral">"baz:1"</span>);</div><div class="line"> });</div><div class="line"></div><div class="line"> events.trigger(BOOST_HANA_STRING(<span class="stringliteral">"foo"</span>));</div><div class="line"> events.trigger(BOOST_HANA_STRING(<span class="stringliteral">"bar"</span>));</div><div class="line"> events.trigger(BOOST_HANA_STRING(<span class="stringliteral">"baz"</span>));</div><div class="line"></div><div class="line"> <a class="code" href="group__group-assertions.html#ga29b2b21ffa5513e5b706c50ffee980af">BOOST_HANA_RUNTIME_CHECK</a>(triggered_events == std::vector<std::string>{</div><div class="line"> <span class="stringliteral">"foo:1"</span>, <span class="stringliteral">"foo:2"</span>, <span class="stringliteral">"bar:1"</span>, <span class="stringliteral">"baz:1"</span></div><div class="line"> });</div><div class="line">}</div></div><!-- fragment --> </div><table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="related"></a>
Synopsis of associated functions</h2></td></tr>
<tr class="memitem:a409d52de54cc7e55eca1a7b5dda4ce30"><td class="memTemplParams" colspan="2">template<> </td></tr>
<tr class="memitem:a409d52de54cc7e55eca1a7b5dda4ce30"><td class="memTemplItemLeft" align="right" valign="top">constexpr auto </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a409d52de54cc7e55eca1a7b5dda4ce30">make< map_tag ></a></td></tr>
<tr class="memdesc:a409d52de54cc7e55eca1a7b5dda4ce30"><td class="mdescLeft"> </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>
<tr class="separator:a409d52de54cc7e55eca1a7b5dda4ce30"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ae73cf43ee56352e4c25984b0fe3c3d04"><td class="memItemLeft" align="right" valign="top">constexpr auto </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><<a class="el" href="structboost_1_1hana_1_1map__tag.html">map_tag</a>></td></tr>
<tr class="memdesc:ae73cf43ee56352e4c25984b0fe3c3d04"><td class="mdescLeft"> </td><td class="mdescRight">Alias to <code>make<<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps. ">map_tag</a>></code>; provided for convenience. <a href="#ae73cf43ee56352e4c25984b0fe3c3d04">More...</a><br /></td></tr>
<tr class="separator:ae73cf43ee56352e4c25984b0fe3c3d04"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a4feb32bd0a065a0732908716d4855b57"><td class="memItemLeft" align="right" valign="top">constexpr auto </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><<a class="el" href="structboost_1_1hana_1_1map__tag.html">map_tag</a>></td></tr>
<tr class="memdesc:a4feb32bd0a065a0732908716d4855b57"><td class="mdescLeft"> </td><td class="mdescRight">Equivalent to <code>to<<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps. ">map_tag</a>></code>; provided for convenience. <a href="#a4feb32bd0a065a0732908716d4855b57">More...</a><br /></td></tr>
<tr class="separator:a4feb32bd0a065a0732908716d4855b57"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a0f32260f859b2510dd16235b7bc011ac"><td class="memItemLeft" align="right" valign="top">constexpr auto </td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a0f32260f859b2510dd16235b7bc011ac">keys</a></td></tr>
<tr class="memdesc:a0f32260f859b2510dd16235b7bc011ac"><td class="mdescLeft"> </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>
<tr class="separator:a0f32260f859b2510dd16235b7bc011ac"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a2e016a68e3ec6eb25868fadb7ce80132"><td class="memItemLeft" align="right" valign="top">constexpr auto </td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a2e016a68e3ec6eb25868fadb7ce80132">values</a></td></tr>
<tr class="memdesc:a2e016a68e3ec6eb25868fadb7ce80132"><td class="mdescLeft"> </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>
<tr class="separator:a2e016a68e3ec6eb25868fadb7ce80132"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a5791e6dc0e27d8e3a113e4d94482550f"><td class="memItemLeft" align="right" valign="top">constexpr auto </td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a5791e6dc0e27d8e3a113e4d94482550f">insert</a></td></tr>
<tr class="memdesc:a5791e6dc0e27d8e3a113e4d94482550f"><td class="mdescLeft"> </td><td class="mdescRight">Inserts a new key/value pair in a map. <a href="#a5791e6dc0e27d8e3a113e4d94482550f">More...</a><br /></td></tr>
<tr class="separator:a5791e6dc0e27d8e3a113e4d94482550f"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:af856f7bf77f69cdf1b8fd4e566eaef9b"><td class="memItemLeft" align="right" valign="top">constexpr auto </td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#af856f7bf77f69cdf1b8fd4e566eaef9b">erase_key</a></td></tr>
<tr class="memdesc:af856f7bf77f69cdf1b8fd4e566eaef9b"><td class="mdescLeft"> </td><td class="mdescRight">Removes a key/value pair from a map. <a href="#af856f7bf77f69cdf1b8fd4e566eaef9b">More...</a><br /></td></tr>
<tr class="separator:af856f7bf77f69cdf1b8fd4e566eaef9b"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:acd511f2c01f38405bfba0b6d5b2922e8"><td class="memItemLeft" align="right" valign="top">constexpr auto </td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#acd511f2c01f38405bfba0b6d5b2922e8">union_</a></td></tr>
<tr class="memdesc:acd511f2c01f38405bfba0b6d5b2922e8"><td class="mdescLeft"> </td><td class="mdescRight">Returns the union of two maps. <a href="#acd511f2c01f38405bfba0b6d5b2922e8">More...</a><br /></td></tr>
<tr class="separator:acd511f2c01f38405bfba0b6d5b2922e8"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a3b3430482d4e88052e621f63a234f3eb"><td class="memItemLeft" align="right" valign="top">constexpr auto </td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a3b3430482d4e88052e621f63a234f3eb">intersection</a></td></tr>
<tr class="memdesc:a3b3430482d4e88052e621f63a234f3eb"><td class="mdescLeft"> </td><td class="mdescRight">Returns the intersection of two maps. <a href="#a3b3430482d4e88052e621f63a234f3eb">More...</a><br /></td></tr>
<tr class="separator:a3b3430482d4e88052e621f63a234f3eb"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a718ddfe86437adbbca1e1a5db651d139"><td class="memItemLeft" align="right" valign="top">constexpr auto </td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a718ddfe86437adbbca1e1a5db651d139">difference</a></td></tr>
<tr class="memdesc:a718ddfe86437adbbca1e1a5db651d139"><td class="mdescLeft"> </td><td class="mdescRight">Returns the difference of two maps. <a href="#a718ddfe86437adbbca1e1a5db651d139">More...</a><br /></td></tr>
<tr class="separator:a718ddfe86437adbbca1e1a5db651d139"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a8bcb2455eb9f7074185d8fb61a99801e"><td class="memItemLeft" align="right" valign="top">constexpr auto </td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a8bcb2455eb9f7074185d8fb61a99801e">symmetric_difference</a></td></tr>
<tr class="memdesc:a8bcb2455eb9f7074185d8fb61a99801e"><td class="mdescLeft"> </td><td class="mdescRight">Returns the symmetric set-theoretic difference of two maps. <a href="#a8bcb2455eb9f7074185d8fb61a99801e">More...</a><br /></td></tr>
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</table><table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="friends"></a>
Friends</h2></td></tr>
<tr class="memitem:a27607958295e6da8a0ba602a2db468f1"><td class="memTemplParams" colspan="2"><a class="anchor" id="a27607958295e6da8a0ba602a2db468f1"></a>
template<typename X , typename Y > </td></tr>
<tr class="memitem:a27607958295e6da8a0ba602a2db468f1"><td class="memTemplItemLeft" align="right" valign="top">constexpr auto </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a27607958295e6da8a0ba602a2db468f1">operator==</a> (X &&x, Y &&y)</td></tr>
<tr class="memdesc:a27607958295e6da8a0ba602a2db468f1"><td class="mdescLeft"> </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>
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<tr class="memitem:a0cae3af55edb3eb05bfa184bda633f7d"><td class="memTemplParams" colspan="2"><a class="anchor" id="a0cae3af55edb3eb05bfa184bda633f7d"></a>
template<typename X , typename Y > </td></tr>
<tr class="memitem:a0cae3af55edb3eb05bfa184bda633f7d"><td class="memTemplItemLeft" align="right" valign="top">constexpr auto </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a0cae3af55edb3eb05bfa184bda633f7d">operator!=</a> (X &&x, Y &&y)</td></tr>
<tr class="memdesc:a0cae3af55edb3eb05bfa184bda633f7d"><td class="mdescLeft"> </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>
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</table><table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="pub-methods"></a>
Public Member Functions</h2></td></tr>
<tr class="memitem:a1ee432be0bd10f08a637a437e311e4e2"><td class="memItemLeft" align="right" valign="top"><a class="anchor" id="a1ee432be0bd10f08a637a437e311e4e2"></a>
constexpr </td><td class="memItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a1ee432be0bd10f08a637a437e311e4e2">map</a> ()=default</td></tr>
<tr class="memdesc:a1ee432be0bd10f08a637a437e311e4e2"><td class="mdescLeft"> </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>
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<tr class="memitem:a943219d1c9692938167639d8ad2525b8"><td class="memItemLeft" align="right" valign="top"><a class="anchor" id="a943219d1c9692938167639d8ad2525b8"></a>
constexpr </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 &other)=default</td></tr>
<tr class="memdesc:a943219d1c9692938167639d8ad2525b8"><td class="mdescLeft"> </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>
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constexpr </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> &&other)=default</td></tr>
<tr class="memdesc:a675bb30af155b40f72cbe8607eefbe4e"><td class="mdescLeft"> </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>
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template<typename... P> </td></tr>
<tr class="memitem:a4a4f472e036abf9bcbda81e831f46e32"><td class="memTemplItemLeft" align="right" valign="top">constexpr </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a4a4f472e036abf9bcbda81e831f46e32">map</a> (P &&...pairs)</td></tr>
<tr class="memdesc:a4a4f472e036abf9bcbda81e831f46e32"><td class="mdescLeft"> </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>
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<tr class="memitem:ae18123925b628b5cfcb1adaef5c83ac7"><td class="memItemLeft" align="right" valign="top"><a class="anchor" id="ae18123925b628b5cfcb1adaef5c83ac7"></a>
constexpr <a class="el" href="structboost_1_1hana_1_1map.html">map</a> & </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 &other)</td></tr>
<tr class="memdesc:ae18123925b628b5cfcb1adaef5c83ac7"><td class="mdescLeft"> </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>
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constexpr <a class="el" href="structboost_1_1hana_1_1map.html">map</a> & </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> &&other)</td></tr>
<tr class="memdesc:a9a6635ea36edc582518d278238defa0d"><td class="mdescLeft"> </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>
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template<typename Key > </td></tr>
<tr class="memitem:a4881a1810986e678959af8ccb58f5666"><td class="memTemplItemLeft" align="right" valign="top">decltype(auto) constexpr </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="structboost_1_1hana_1_1map.html#a4881a1810986e678959af8ccb58f5666">operator[]</a> (Key &&key)</td></tr>
<tr class="memdesc:a4881a1810986e678959af8ccb58f5666"><td class="mdescLeft"> </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>
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<h2 class="groupheader">Associated functions</h2>
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<div class="memitem">
<div class="memproto">
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template<typename... Pairs> </div>
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<b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&& ...pairs) {</div><div class="line"> <span class="keywordflow">return</span> map<implementation_defined>{forwarded(pairs)...};</div><div class="line"> }</div></div><!-- fragment -->
<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>
<p>Given zero or more <code>Product</code>s representing key/value associations, <code>make<<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps. ">map_tag</a>></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>
<p><code>make<<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps. ">map_tag</a>></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<<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps. ">map_tag</a>></code>, because the uniqueness of keys will have to be enforced.</p>
<h2>Example </h2>
<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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="core_2make_8hpp.html">boost/hana/core/make.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>></span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <string></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#ga29b2b21ffa5513e5b706c50ffee980af">BOOST_HANA_RUNTIME_CHECK</a>(</div><div class="line"> hana::make_map(</div><div class="line"> hana::make_pair(hana::int_c<1>, <span class="stringliteral">"foobar"</span>s),</div><div class="line"> hana::make_pair(hana::type_c<void>, 1234)</div><div class="line"> )</div><div class="line"> ==</div><div class="line"> hana::make<hana::map_tag>(</div><div class="line"> hana::make_pair(hana::int_c<1>, <span class="stringliteral">"foobar"</span>s),</div><div class="line"> hana::make_pair(hana::type_c<void>, 1234)</div><div class="line"> )</div><div class="line"> );</div><div class="line">}</div></div><!-- fragment -->
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<p>Alias to <code>make<<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps. ">map_tag</a>></code>; provided for convenience. </p>
<h2>Example </h2>
<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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="core_2make_8hpp.html">boost/hana/core/make.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>></span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <string></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#ga29b2b21ffa5513e5b706c50ffee980af">BOOST_HANA_RUNTIME_CHECK</a>(</div><div class="line"> hana::make_map(</div><div class="line"> hana::make_pair(hana::int_c<1>, <span class="stringliteral">"foobar"</span>s),</div><div class="line"> hana::make_pair(hana::type_c<void>, 1234)</div><div class="line"> )</div><div class="line"> ==</div><div class="line"> hana::make<hana::map_tag>(</div><div class="line"> hana::make_pair(hana::int_c<1>, <span class="stringliteral">"foobar"</span>s),</div><div class="line"> hana::make_pair(hana::type_c<void>, 1234)</div><div class="line"> )</div><div class="line"> );</div><div class="line">}</div></div><!-- fragment -->
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<p>Equivalent to <code>to<<a class="el" href="structboost_1_1hana_1_1map__tag.html" title="Tag representing hana::maps. ">map_tag</a>></code>; provided for convenience. </p>
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<b>Initial value:</b><div class="fragment"><div class="line">= [](<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> implementation_defined;</div><div class="line"> }</div></div><!-- fragment -->
<p>Returns a <code>Sequence</code> of the keys of the map, in unspecified order. </p>
<h2>Example </h2>
<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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="contains_8hpp.html">boost/hana/contains.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="keys_8hpp.html">boost/hana/keys.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="permutations_8hpp.html">boost/hana/permutations.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="tuple_8hpp.html">boost/hana/tuple.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>></span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <string></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<1>, <span class="stringliteral">"foobar"</span>s),</div><div class="line"> hana::make_pair(hana::type_c<void>, 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#ga4bf9e0c46c44e21fbe5c5fbb3ace8356">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<1>, hana::type_c<void>))</div><div class="line"> );</div><div class="line">}</div></div><!-- fragment -->
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<b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&& <a class="code" href="structboost_1_1hana_1_1map.html#a1ee432be0bd10f08a637a437e311e4e2">map</a>) -> decltype(<span class="keyword">auto</span>) {</div><div class="line"> <span class="keywordflow">return</span> implementation_defined;</div><div class="line"> }</div></div><!-- fragment -->
<p>Returns a <code>Sequence</code> of the values of the map, in unspecified order. </p>
<h2>Example </h2>
<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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="contains_8hpp.html">boost/hana/contains.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="permutations_8hpp.html">boost/hana/permutations.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="tuple_8hpp.html">boost/hana/tuple.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>></span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <string></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<1>, <span class="stringliteral">"foobar"</span>s),</div><div class="line"> hana::make_pair(hana::type_c<void>, 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#ga29b2b21ffa5513e5b706c50ffee980af">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">"foobar"</span>s, 1234))</div><div class="line"> );</div><div class="line">}</div></div><!-- fragment -->
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<b>Initial value:</b><div class="fragment"><div class="line">= [](<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> tag-dispatched;</div><div class="line"> }</div></div><!-- fragment -->
<p>Inserts a new key/value pair in a map. </p>
<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>
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<h2>Example </h2>
<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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="insert_8hpp.html">boost/hana/insert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>></span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <string></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<int>, <span class="stringliteral">"abcd"</span>s),</div><div class="line"> hana::make_pair(hana::type_c<void>, 1234)</div><div class="line"> );</div><div class="line"></div><div class="line"> <a class="code" href="group__group-assertions.html#ga29b2b21ffa5513e5b706c50ffee980af">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<float>, <span class="charliteral">'x'</span>)) ==</div><div class="line"> hana::make_map(</div><div class="line"> hana::make_pair(hana::type_c<int>, <span class="stringliteral">"abcd"</span>s),</div><div class="line"> hana::make_pair(hana::type_c<void>, 1234),</div><div class="line"> hana::make_pair(hana::type_c<float>, <span class="charliteral">'x'</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#ga29b2b21ffa5513e5b706c50ffee980af">BOOST_HANA_RUNTIME_CHECK</a>(<a class="code" href="group__group-Sequence.html#gae22a1a184b1b2dd550fa4fa619bed2e9">hana::insert</a>(m, hana::make_pair(hana::type_c<void>, <span class="charliteral">'x'</span>)) == m);</div><div class="line">}</div></div><!-- fragment -->
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<b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&& <a class="code" href="structboost_1_1hana_1_1map.html#a1ee432be0bd10f08a637a437e311e4e2">map</a>, <span class="keyword">auto</span>&& key) {</div><div class="line"> <span class="keywordflow">return</span> tag-dispatched;</div><div class="line"> }</div></div><!-- fragment -->
<p>Removes a key/value pair from a map. </p>
<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>
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<h2>Example </h2>
<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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="erase__key_8hpp.html">boost/hana/erase_key.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="pair_8hpp.html">boost/hana/pair.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="string_8hpp.html">boost/hana/string.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>></span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <string></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<int>, <span class="stringliteral">"abcd"</span>s),</div><div class="line"> hana::make_pair(hana::type_c<void>, 1234),</div><div class="line"> hana::make_pair(BOOST_HANA_STRING(<span class="stringliteral">"foobar!"</span>), hana::type_c<char>)</div><div class="line"> );</div><div class="line"></div><div class="line"> <a class="code" href="group__group-assertions.html#ga29b2b21ffa5513e5b706c50ffee980af">BOOST_HANA_RUNTIME_CHECK</a>(</div><div class="line"> hana::erase_key(m, BOOST_HANA_STRING(<span class="stringliteral">"foobar!"</span>)) ==</div><div class="line"> hana::make_map(</div><div class="line"> hana::make_pair(hana::type_c<int>, <span class="stringliteral">"abcd"</span>s),</div><div class="line"> hana::make_pair(hana::type_c<void>, 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#ga29b2b21ffa5513e5b706c50ffee980af">BOOST_HANA_RUNTIME_CHECK</a>(hana::erase_key(m, hana::type_c<char>) == m);</div><div class="line">}</div></div><!-- fragment -->
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<b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&& xs, <span class="keyword">auto</span>&& ys) {</div><div class="line"> <span class="keywordflow">return</span> tag-dispatched;</div><div class="line"> }</div></div><!-- fragment -->
<p>Returns the union of two maps. </p>
<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>
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<h2>Example </h2>
<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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="equal_8hpp.html">boost/hana/equal.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="integral__constant_8hpp.html">boost/hana/integral_constant.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="string_8hpp.html">boost/hana/string.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="type_8hpp.html">boost/hana/type.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="union_8hpp.html">boost/hana/union.hpp</a>></span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <string></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">constexpr <span class="keyword">auto</span> m1 = hana::make_map(</div><div class="line"> hana::make_pair(<span class="stringliteral">"key1"</span>_s, hana::type_c<std::string>),</div><div class="line"> hana::make_pair(<span class="stringliteral">"key2"</span>_s, hana::type_c<std::string>)</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(<span class="stringliteral">"key3"</span>_s, hana::type_c<std::string>),</div><div class="line"> hana::make_pair(<span class="stringliteral">"key4"</span>_s, hana::type_c<std::string>),</div><div class="line"> hana::make_pair(<span class="stringliteral">"key5"</span>_s, hana::type_c<std::string>)</div><div class="line">);</div><div class="line"></div><div class="line"><a class="code" href="group__group-assertions.html#ga4bf9e0c46c44e21fbe5c5fbb3ace8356">BOOST_HANA_CONSTANT_CHECK</a>(hana::union_(m1, m2) == hana::make_map(</div><div class="line"> hana::make_pair(<span class="stringliteral">"key1"</span>_s, hana::type_c<std::string>),</div><div class="line"> hana::make_pair(<span class="stringliteral">"key2"</span>_s, hana::type_c<std::string>),</div><div class="line"> hana::make_pair(<span class="stringliteral">"key3"</span>_s, hana::type_c<std::string>),</div><div class="line"> hana::make_pair(<span class="stringliteral">"key4"</span>_s, hana::type_c<std::string>),</div><div class="line"> hana::make_pair(<span class="stringliteral">"key5"</span>_s, hana::type_c<std::string>)</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<int>, hana::int_c<1>),</div><div class="line"> hana::make_pair(hana::type_c<bool>, hana::bool_c<true>)</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<char>, hana::char_c<'c'>),</div><div class="line"> hana::make_pair(hana::type_c<bool>, hana::bool_c<false>)</div><div class="line">);</div><div class="line"></div><div class="line"><a class="code" href="group__group-assertions.html#ga4bf9e0c46c44e21fbe5c5fbb3ace8356">BOOST_HANA_CONSTANT_CHECK</a>(hana::union_(m3, m4) == hana::make_map(</div><div class="line"> hana::make_pair(hana::type_c<int>, hana::int_c<1>),</div><div class="line"> hana::make_pair(hana::type_c<bool>, hana::bool_c<false>),</div><div class="line"> hana::make_pair(hana::type_c<char>, hana::char_c<'c'>)</div><div class="line">));</div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() { }</div></div><!-- fragment -->
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<b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&& xs, <span class="keyword">auto</span>&& ys) {</div><div class="line"> <span class="keywordflow">return</span> tag-dispatched;</div><div class="line"> }</div></div><!-- fragment -->
<p>Returns the intersection of two maps. </p>
<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) if and only if (k, v) ^<a class="code" href="group__group-Searchable.html#ga0d9456ceda38b6ca664998e79d7c45b7">in</a>^ xs && 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>
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<h2>Example </h2>
<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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="equal_8hpp.html">boost/hana/equal.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="intersection_8hpp.html">boost/hana/intersection.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="string_8hpp.html">boost/hana/string.hpp</a>></span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <string></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">constexpr <span class="keyword">auto</span> m1 = hana::make_map(</div><div class="line"> hana::make_pair(<span class="stringliteral">"key1"</span>_s, hana::type_c<std::string>),</div><div class="line"> hana::make_pair(<span class="stringliteral">"key2"</span>_s, hana::type_c<std::string>)</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(<span class="stringliteral">"key3"</span>_s, hana::type_c<std::string>),</div><div class="line"> hana::make_pair(<span class="stringliteral">"key4"</span>_s, hana::type_c<std::string>),</div><div class="line"> hana::make_pair(<span class="stringliteral">"key5"</span>_s, hana::type_c<std::string>)</div><div class="line">);</div><div class="line"></div><div class="line"><a class="code" href="group__group-assertions.html#ga4bf9e0c46c44e21fbe5c5fbb3ace8356">BOOST_HANA_CONSTANT_CHECK</a>(hana::intersection(m1, m2) == hana::make_map());</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<int>, hana::int_c<1>),</div><div class="line"> hana::make_pair(hana::type_c<bool>, hana::bool_c<true>),</div><div class="line"> hana::make_pair(hana::type_c<std::string>, <span class="stringliteral">"hana"</span>_s),</div><div class="line"> hana::make_pair(hana::type_c<float>, hana::int_c<100>)</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<char>, hana::char_c<'c'>),</div><div class="line"> hana::make_pair(hana::type_c<bool>, hana::bool_c<false>),</div><div class="line"> hana::make_pair(hana::type_c<std::string>, <span class="stringliteral">"boost"</span>_s)</div><div class="line">);</div><div class="line"></div><div class="line"><a class="code" href="group__group-assertions.html#ga4bf9e0c46c44e21fbe5c5fbb3ace8356">BOOST_HANA_CONSTANT_CHECK</a>(hana::intersection(m3, m4) == hana::make_map(</div><div class="line"> hana::make_pair(hana::type_c<bool>, hana::bool_c<true>),</div><div class="line"> hana::make_pair(hana::type_c<std::string>, <span class="stringliteral">"hana"</span>_s)</div><div class="line">));</div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() { }</div></div><!-- fragment -->
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<b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&& xs, <span class="keyword">auto</span>&& ys) {</div><div class="line"> <span class="keywordflow">return</span> tag-dispatched;</div><div class="line"> }</div></div><!-- fragment -->
<p>Returns the difference of two maps. </p>
<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) if and only if (k, v) ^<a class="code" href="group__group-Searchable.html#ga0d9456ceda38b6ca664998e79d7c45b7">in</a>^ xs && 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>
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<h2>Example </h2>
<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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="equal_8hpp.html">boost/hana/equal.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="intersection_8hpp.html">boost/hana/intersection.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="string_8hpp.html">boost/hana/string.hpp</a>></span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <string></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">constexpr <span class="keyword">auto</span> m1 = hana::make_map(</div><div class="line"> hana::make_pair(<span class="stringliteral">"key1"</span>_s, hana::type_c<std::string>),</div><div class="line"> hana::make_pair(<span class="stringliteral">"key2"</span>_s, hana::type_c<std::string>)</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(<span class="stringliteral">"key3"</span>_s, hana::type_c<std::string>),</div><div class="line"> hana::make_pair(<span class="stringliteral">"key4"</span>_s, hana::type_c<std::string>),</div><div class="line"> hana::make_pair(<span class="stringliteral">"key5"</span>_s, hana::type_c<std::string>)</div><div class="line">);</div><div class="line"></div><div class="line"><a class="code" href="group__group-assertions.html#ga4bf9e0c46c44e21fbe5c5fbb3ace8356">BOOST_HANA_CONSTANT_CHECK</a>(hana::intersection(m1, m2) == hana::make_map());</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<int>, hana::int_c<1>),</div><div class="line"> hana::make_pair(hana::type_c<bool>, hana::bool_c<true>),</div><div class="line"> hana::make_pair(hana::type_c<std::string>, <span class="stringliteral">"hana"</span>_s),</div><div class="line"> hana::make_pair(hana::type_c<float>, hana::int_c<100>)</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<char>, hana::char_c<'c'>),</div><div class="line"> hana::make_pair(hana::type_c<bool>, hana::bool_c<false>),</div><div class="line"> hana::make_pair(hana::type_c<std::string>, <span class="stringliteral">"boost"</span>_s)</div><div class="line">);</div><div class="line"></div><div class="line"><a class="code" href="group__group-assertions.html#ga4bf9e0c46c44e21fbe5c5fbb3ace8356">BOOST_HANA_CONSTANT_CHECK</a>(hana::intersection(m3, m4) == hana::make_map(</div><div class="line"> hana::make_pair(hana::type_c<bool>, hana::bool_c<true>),</div><div class="line"> hana::make_pair(hana::type_c<std::string>, <span class="stringliteral">"hana"</span>_s)</div><div class="line">));</div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() { }</div></div><!-- fragment -->
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<b>Initial value:</b><div class="fragment"><div class="line">= [](<span class="keyword">auto</span>&& xs, <span class="keyword">auto</span>&& ys) {</div><div class="line"> <span class="keywordflow">return</span> tag-dispatched;</div><div class="line"> }</div></div><!-- fragment -->
<p>Returns the symmetric set-theoretic difference of two maps. </p>
<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>
<table class="params">
<tr><td class="paramname">xs,ys</td><td>Two maps to compute the symmetric difference of.</td></tr>
</table>
</dd>
</dl>
<h2>Example </h2>
<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 <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="map_8hpp.html">boost/hana/map.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="symmetric__difference_8hpp.html">boost/hana/symmetric_difference.hpp</a>></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<int>, 1),</div><div class="line"> hana::make_pair(hana::type_c<bool>, 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<float>, 1.0),</div><div class="line"> hana::make_pair(hana::type_c<long long>, 2LL),</div><div class="line"> hana::make_pair(hana::type_c<int>, 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<bool>, hana::true_c),</div><div class="line"> hana::make_pair(hana::type_c<float>, 1.0),</div><div class="line"> hana::make_pair(hana::type_c<long long>, 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#ga29b2b21ffa5513e5b706c50ffee980af">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 -->
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