<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/>
<meta http-equiv="X-UA-Compatible" content="IE=9"/>
<meta name="generator" content="Doxygen 1.8.15"/>
<meta name="viewport" content="width=device-width, initial-scale=1"/>
<title>libstdc++: optional Source File</title>
<link href="tabs.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript" src="dynsections.js"></script>
<link href="navtree.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="resize.js"></script>
<script type="text/javascript" src="navtreedata.js"></script>
<script type="text/javascript" src="navtree.js"></script>
<script type="text/javascript">
/* @license magnet:?xt=urn:btih:cf05388f2679ee054f2beb29a391d25f4e673ac3&dn=gpl-2.0.txt GPL-v2 */
$(document).ready(initResizable);
/* @license-end */</script>
<link href="doxygen.css" rel="stylesheet" type="text/css" />
</head>
<body>
<div id="top"><!-- do not remove this div, it is closed by doxygen! -->
<div id="titlearea">
<table cellspacing="0" cellpadding="0">
<tbody>
<tr style="height: 56px;">
<td id="projectalign" style="padding-left: 0.5em;">
<div id="projectname">libstdc++
</div>
</td>
</tr>
</tbody>
</table>
</div>
<!-- end header part -->
<!-- Generated by Doxygen 1.8.15 -->
</div><!-- top -->
<div id="side-nav" class="ui-resizable side-nav-resizable">
<div id="nav-tree">
<div id="nav-tree-contents">
<div id="nav-sync" class="sync"></div>
</div>
</div>
<div id="splitbar" style="-moz-user-select:none;"
class="ui-resizable-handle">
</div>
</div>
<script type="text/javascript">
/* @license magnet:?xt=urn:btih:cf05388f2679ee054f2beb29a391d25f4e673ac3&dn=gpl-2.0.txt GPL-v2 */
$(document).ready(function(){initNavTree('a01007_source.html','');});
/* @license-end */
</script>
<div id="doc-content">
<div class="header">
<div class="headertitle">
<div class="title">optional</div> </div>
</div><!--header-->
<div class="contents">
<a href="a01007.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> <span class="comment">// <optional> -*- C++ -*-</span></div><div class="line"><a name="l00002"></a><span class="lineno"> 2</span> </div><div class="line"><a name="l00003"></a><span class="lineno"> 3</span> <span class="comment">// Copyright (C) 2013-2018 Free Software Foundation, Inc.</span></div><div class="line"><a name="l00004"></a><span class="lineno"> 4</span> <span class="comment">//</span></div><div class="line"><a name="l00005"></a><span class="lineno"> 5</span> <span class="comment">// This file is part of the GNU ISO C++ Library. This library is free</span></div><div class="line"><a name="l00006"></a><span class="lineno"> 6</span> <span class="comment">// software; you can redistribute it and/or modify it under the</span></div><div class="line"><a name="l00007"></a><span class="lineno"> 7</span> <span class="comment">// terms of the GNU General Public License as published by the</span></div><div class="line"><a name="l00008"></a><span class="lineno"> 8</span> <span class="comment">// Free Software Foundation; either version 3, or (at your option)</span></div><div class="line"><a name="l00009"></a><span class="lineno"> 9</span> <span class="comment">// any later version.</span></div><div class="line"><a name="l00010"></a><span class="lineno"> 10</span> </div><div class="line"><a name="l00011"></a><span class="lineno"> 11</span> <span class="comment">// This library is distributed in the hope that it will be useful,</span></div><div class="line"><a name="l00012"></a><span class="lineno"> 12</span> <span class="comment">// but WITHOUT ANY WARRANTY; without even the implied warranty of</span></div><div class="line"><a name="l00013"></a><span class="lineno"> 13</span> <span class="comment">// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the</span></div><div class="line"><a name="l00014"></a><span class="lineno"> 14</span> <span class="comment">// GNU General Public License for more details.</span></div><div class="line"><a name="l00015"></a><span class="lineno"> 15</span> </div><div class="line"><a name="l00016"></a><span class="lineno"> 16</span> <span class="comment">// Under Section 7 of GPL version 3, you are granted additional</span></div><div class="line"><a name="l00017"></a><span class="lineno"> 17</span> <span class="comment">// permissions described in the GCC Runtime Library Exception, version</span></div><div class="line"><a name="l00018"></a><span class="lineno"> 18</span> <span class="comment">// 3.1, as published by the Free Software Foundation.</span></div><div class="line"><a name="l00019"></a><span class="lineno"> 19</span> </div><div class="line"><a name="l00020"></a><span class="lineno"> 20</span> <span class="comment">// You should have received a copy of the GNU General Public License and</span></div><div class="line"><a name="l00021"></a><span class="lineno"> 21</span> <span class="comment">// a copy of the GCC Runtime Library Exception along with this program;</span></div><div class="line"><a name="l00022"></a><span class="lineno"> 22</span> <span class="comment">// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see</span></div><div class="line"><a name="l00023"></a><span class="lineno"> 23</span> <span class="comment">// <http://www.gnu.org/licenses/>.</span></div><div class="line"><a name="l00024"></a><span class="lineno"> 24</span> <span class="comment"></span></div><div class="line"><a name="l00025"></a><span class="lineno"> 25</span> <span class="comment">/** @file experimental/optional</span></div><div class="line"><a name="l00026"></a><span class="lineno"> 26</span> <span class="comment"> * This is a TS C++ Library header.</span></div><div class="line"><a name="l00027"></a><span class="lineno"> 27</span> <span class="comment"> */</span></div><div class="line"><a name="l00028"></a><span class="lineno"> 28</span> </div><div class="line"><a name="l00029"></a><span class="lineno"> 29</span> <span class="preprocessor">#ifndef _GLIBCXX_EXPERIMENTAL_OPTIONAL</span></div><div class="line"><a name="l00030"></a><span class="lineno"> 30</span> <span class="preprocessor">#define _GLIBCXX_EXPERIMENTAL_OPTIONAL 1</span></div><div class="line"><a name="l00031"></a><span class="lineno"> 31</span> <span class="comment"></span></div><div class="line"><a name="l00032"></a><span class="lineno"> 32</span> <span class="comment">/**</span></div><div class="line"><a name="l00033"></a><span class="lineno"> 33</span> <span class="comment"> * @defgroup experimental Experimental</span></div><div class="line"><a name="l00034"></a><span class="lineno"> 34</span> <span class="comment"> *</span></div><div class="line"><a name="l00035"></a><span class="lineno"> 35</span> <span class="comment"> * Components specified by various Technical Specifications.</span></div><div class="line"><a name="l00036"></a><span class="lineno"> 36</span> <span class="comment"> *</span></div><div class="line"><a name="l00037"></a><span class="lineno"> 37</span> <span class="comment"> * As indicated by the std::experimental namespace and the header paths,</span></div><div class="line"><a name="l00038"></a><span class="lineno"> 38</span> <span class="comment"> * the contents of these Technical Specifications are experimental and not</span></div><div class="line"><a name="l00039"></a><span class="lineno"> 39</span> <span class="comment"> * part of the C++ standard. As such the interfaces and implementations may</span></div><div class="line"><a name="l00040"></a><span class="lineno"> 40</span> <span class="comment"> * change in the future, and there is <STRONG> no guarantee of compatibility</span></div><div class="line"><a name="l00041"></a><span class="lineno"> 41</span> <span class="comment"> * between different GCC releases </STRONG> for these features.</span></div><div class="line"><a name="l00042"></a><span class="lineno"> 42</span> <span class="comment"> */</span></div><div class="line"><a name="l00043"></a><span class="lineno"> 43</span> </div><div class="line"><a name="l00044"></a><span class="lineno"> 44</span> <span class="preprocessor">#if __cplusplus >= 201402L</span></div><div class="line"><a name="l00045"></a><span class="lineno"> 45</span> </div><div class="line"><a name="l00046"></a><span class="lineno"> 46</span> <span class="preprocessor">#include <<a class="code" href="a17232.html">utility</a>></span></div><div class="line"><a name="l00047"></a><span class="lineno"> 47</span> <span class="preprocessor">#include <<a class="code" href="a17211.html">type_traits</a>></span></div><div class="line"><a name="l00048"></a><span class="lineno"> 48</span> <span class="preprocessor">#include <<a class="code" href="a00146.html">stdexcept</a>></span></div><div class="line"><a name="l00049"></a><span class="lineno"> 49</span> <span class="preprocessor">#include <<a class="code" href="a00032.html">new</a>></span></div><div class="line"><a name="l00050"></a><span class="lineno"> 50</span> <span class="preprocessor">#include <<a class="code" href="a00029.html">initializer_list</a>></span></div><div class="line"><a name="l00051"></a><span class="lineno"> 51</span> <span class="preprocessor">#include <<a class="code" href="a00356.html">bits/functexcept.h</a>></span></div><div class="line"><a name="l00052"></a><span class="lineno"> 52</span> <span class="preprocessor">#include <<a class="code" href="a00359.html">bits/functional_hash.h</a>></span></div><div class="line"><a name="l00053"></a><span class="lineno"> 53</span> <span class="preprocessor">#include <<a class="code" href="a00323.html">bits/enable_special_members.h</a>></span></div><div class="line"><a name="l00054"></a><span class="lineno"> 54</span> <span class="preprocessor">#include <<a class="code" href="a00995.html">experimental/bits/lfts_config.h</a>></span></div><div class="line"><a name="l00055"></a><span class="lineno"> 55</span> </div><div class="line"><a name="l00056"></a><span class="lineno"> 56</span> <span class="keyword">namespace </span><a class="code" href="a01538.html">std</a> _GLIBCXX_VISIBILITY(default)</div><div class="line"><a name="l00057"></a><span class="lineno"> 57</span> {</div><div class="line"><a name="l00058"></a><span class="lineno"> 58</span> _GLIBCXX_BEGIN_NAMESPACE_VERSION</div><div class="line"><a name="l00059"></a><span class="lineno"> 59</span> </div><div class="line"><a name="l00060"></a><span class="lineno"> 60</span> <span class="keyword">namespace </span>experimental</div><div class="line"><a name="l00061"></a><span class="lineno"> 61</span> {</div><div class="line"><a name="l00062"></a><span class="lineno"> 62</span> <span class="keyword">inline</span> <span class="keyword">namespace </span>fundamentals_v1</div><div class="line"><a name="l00063"></a><span class="lineno"> 63</span> {<span class="comment"></span></div><div class="line"><a name="l00064"></a><span class="lineno"> 64</span> <span class="comment"> /**</span></div><div class="line"><a name="l00065"></a><span class="lineno"> 65</span> <span class="comment"> * @defgroup optional Optional values</span></div><div class="line"><a name="l00066"></a><span class="lineno"> 66</span> <span class="comment"> * @ingroup experimental</span></div><div class="line"><a name="l00067"></a><span class="lineno"> 67</span> <span class="comment"> *</span></div><div class="line"><a name="l00068"></a><span class="lineno"> 68</span> <span class="comment"> * Class template for optional values and surrounding facilities, as</span></div><div class="line"><a name="l00069"></a><span class="lineno"> 69</span> <span class="comment"> * described in n3793 "A proposal to add a utility class to represent</span></div><div class="line"><a name="l00070"></a><span class="lineno"> 70</span> <span class="comment"> * optional objects (Revision 5)".</span></div><div class="line"><a name="l00071"></a><span class="lineno"> 71</span> <span class="comment"> *</span></div><div class="line"><a name="l00072"></a><span class="lineno"> 72</span> <span class="comment"> * @{</span></div><div class="line"><a name="l00073"></a><span class="lineno"> 73</span> <span class="comment"> */</span></div><div class="line"><a name="l00074"></a><span class="lineno"> 74</span> </div><div class="line"><a name="l00075"></a><span class="lineno"> 75</span> <span class="preprocessor">#define __cpp_lib_experimental_optional 201411</span></div><div class="line"><a name="l00076"></a><span class="lineno"> 76</span> </div><div class="line"><a name="l00077"></a><span class="lineno"> 77</span>  <span class="comment">// All subsequent [X.Y.n] references are against n3793.</span></div><div class="line"><a name="l00078"></a><span class="lineno"> 78</span> </div><div class="line"><a name="l00079"></a><span class="lineno"> 79</span>  <span class="comment">// [X.Y.4]</span></div><div class="line"><a name="l00080"></a><span class="lineno"> 80</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00081"></a><span class="lineno"><a class="line" href="a09988.html"> 81</a></span>  <span class="keyword">class </span><a class="code" href="a09988.html">optional</a>;</div><div class="line"><a name="l00082"></a><span class="lineno"> 82</span> </div><div class="line"><a name="l00083"></a><span class="lineno"> 83</span>  <span class="comment">// [X.Y.5]</span><span class="comment"></span></div><div class="line"><a name="l00084"></a><span class="lineno"> 84</span> <span class="comment"> /// Tag type for in-place construction.</span></div><div class="line"><a name="l00085"></a><span class="lineno"><a class="line" href="a09992.html"> 85</a></span> <span class="comment"></span> <span class="keyword">struct </span><a class="code" href="a09992.html">in_place_t</a> { };</div><div class="line"><a name="l00086"></a><span class="lineno"> 86</span> <span class="comment"></span></div><div class="line"><a name="l00087"></a><span class="lineno"> 87</span> <span class="comment"> /// Tag for in-place construction.</span></div><div class="line"><a name="l00088"></a><span class="lineno"><a class="line" href="a01515.html#ga69b3880c858acc1b7f88478d209b2fb3"> 88</a></span> <span class="comment"></span> constexpr <a class="code" href="a09992.html">in_place_t</a> <a class="code" href="a01515.html#ga69b3880c858acc1b7f88478d209b2fb3">in_place</a> { };</div><div class="line"><a name="l00089"></a><span class="lineno"> 89</span> </div><div class="line"><a name="l00090"></a><span class="lineno"> 90</span>  <span class="comment">// [X.Y.6]</span><span class="comment"></span></div><div class="line"><a name="l00091"></a><span class="lineno"> 91</span> <span class="comment"> /// Tag type to disengage optional objects.</span></div><div class="line"><a name="l00092"></a><span class="lineno"><a class="line" href="a09996.html"> 92</a></span> <span class="comment"></span> <span class="keyword">struct </span><a class="code" href="a09996.html">nullopt_t</a></div><div class="line"><a name="l00093"></a><span class="lineno"> 93</span>  {</div><div class="line"><a name="l00094"></a><span class="lineno"> 94</span>  <span class="comment">// Do not user-declare default constructor at all for</span></div><div class="line"><a name="l00095"></a><span class="lineno"> 95</span>  <span class="comment">// optional_value = {} syntax to work.</span></div><div class="line"><a name="l00096"></a><span class="lineno"> 96</span>  <span class="comment">// nullopt_t() = delete;</span></div><div class="line"><a name="l00097"></a><span class="lineno"> 97</span> </div><div class="line"><a name="l00098"></a><span class="lineno"> 98</span>  <span class="comment">// Used for constructing nullopt.</span></div><div class="line"><a name="l00099"></a><span class="lineno"> 99</span>  <span class="keyword">enum class</span> _Construct { _Token };</div><div class="line"><a name="l00100"></a><span class="lineno"> 100</span> </div><div class="line"><a name="l00101"></a><span class="lineno"> 101</span>  <span class="comment">// Must be constexpr for nullopt_t to be literal.</span></div><div class="line"><a name="l00102"></a><span class="lineno"> 102</span>  <span class="keyword">explicit</span> constexpr <a class="code" href="a09996.html">nullopt_t</a>(_Construct) { }</div><div class="line"><a name="l00103"></a><span class="lineno"> 103</span>  };</div><div class="line"><a name="l00104"></a><span class="lineno"> 104</span> </div><div class="line"><a name="l00105"></a><span class="lineno"> 105</span>  <span class="comment">// [X.Y.6]</span><span class="comment"></span></div><div class="line"><a name="l00106"></a><span class="lineno"> 106</span> <span class="comment"> /// Tag to disengage optional objects.</span></div><div class="line"><a name="l00107"></a><span class="lineno"><a class="line" href="a01515.html#ga2221e221b29838a39e88d176b5859900"> 107</a></span> <span class="comment"></span> constexpr <a class="code" href="a09996.html">nullopt_t</a> <a class="code" href="a01515.html#ga2221e221b29838a39e88d176b5859900">nullopt</a> { nullopt_t::_Construct::_Token };</div><div class="line"><a name="l00108"></a><span class="lineno"> 108</span> </div><div class="line"><a name="l00109"></a><span class="lineno"> 109</span>  <span class="comment">// [X.Y.7]</span><span class="comment"></span></div><div class="line"><a name="l00110"></a><span class="lineno"> 110</span> <span class="comment"> /**</span></div><div class="line"><a name="l00111"></a><span class="lineno"> 111</span> <span class="comment"> * @brief Exception class thrown when a disengaged optional object is</span></div><div class="line"><a name="l00112"></a><span class="lineno"> 112</span> <span class="comment"> * dereferenced.</span></div><div class="line"><a name="l00113"></a><span class="lineno"> 113</span> <span class="comment"> * @ingroup exceptions</span></div><div class="line"><a name="l00114"></a><span class="lineno"> 114</span> <span class="comment"> */</span></div><div class="line"><a name="l00115"></a><span class="lineno"><a class="line" href="a10000.html"> 115</a></span>  <span class="keyword">class </span><a class="code" href="a10000.html">bad_optional_access</a> : <span class="keyword">public</span> <a class="code" href="a02784.html">logic_error</a></div><div class="line"><a name="l00116"></a><span class="lineno"> 116</span>  {</div><div class="line"><a name="l00117"></a><span class="lineno"> 117</span>  <span class="keyword">public</span>:</div><div class="line"><a name="l00118"></a><span class="lineno"> 118</span>  <a class="code" href="a10000.html">bad_optional_access</a>() : <a class="code" href="a02784.html#a48e6f223bbd547dcea0d5efdb54b4951">logic_error</a>(<span class="stringliteral">"bad optional access"</span>) { }</div><div class="line"><a name="l00119"></a><span class="lineno"> 119</span> </div><div class="line"><a name="l00120"></a><span class="lineno"> 120</span>  <span class="comment">// XXX This constructor is non-standard. Should not be inline</span></div><div class="line"><a name="l00121"></a><span class="lineno"> 121</span>  <span class="keyword">explicit</span> <a class="code" href="a10000.html">bad_optional_access</a>(<span class="keyword">const</span> <span class="keywordtype">char</span>* __arg) : <a class="code" href="a02784.html#a48e6f223bbd547dcea0d5efdb54b4951">logic_error</a>(__arg) { }</div><div class="line"><a name="l00122"></a><span class="lineno"> 122</span> </div><div class="line"><a name="l00123"></a><span class="lineno"> 123</span>  <span class="keyword">virtual</span> ~<a class="code" href="a10000.html">bad_optional_access</a>() noexcept = <span class="keywordflow">default</span>;</div><div class="line"><a name="l00124"></a><span class="lineno"> 124</span>  };</div><div class="line"><a name="l00125"></a><span class="lineno"> 125</span> </div><div class="line"><a name="l00126"></a><span class="lineno"> 126</span>  <span class="keywordtype">void</span></div><div class="line"><a name="l00127"></a><span class="lineno"> 127</span>  __throw_bad_optional_access(<span class="keyword">const</span> <span class="keywordtype">char</span>*)</div><div class="line"><a name="l00128"></a><span class="lineno"> 128</span>  __attribute__((__noreturn__));</div><div class="line"><a name="l00129"></a><span class="lineno"> 129</span> </div><div class="line"><a name="l00130"></a><span class="lineno"> 130</span>  <span class="comment">// XXX Does not belong here.</span></div><div class="line"><a name="l00131"></a><span class="lineno"> 131</span>  <span class="keyword">inline</span> <span class="keywordtype">void</span></div><div class="line"><a name="l00132"></a><span class="lineno"> 132</span>  __throw_bad_optional_access(<span class="keyword">const</span> <span class="keywordtype">char</span>* __s)</div><div class="line"><a name="l00133"></a><span class="lineno"> 133</span>  { _GLIBCXX_THROW_OR_ABORT(<a class="code" href="a10000.html">bad_optional_access</a>(__s)); }</div><div class="line"><a name="l00134"></a><span class="lineno"> 134</span> </div><div class="line"><a name="l00135"></a><span class="lineno"> 135</span> <span class="preprocessor">#ifndef __cpp_lib_addressof_constexpr</span></div><div class="line"><a name="l00136"></a><span class="lineno"> 136</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp, <span class="keyword">typename</span> = <span class="keywordtype">void</span>></div><div class="line"><a name="l00137"></a><span class="lineno"> 137</span>  <span class="keyword">struct </span>_Has_addressof_mem : <a class="code" href="a03040.html">std::false_type</a> { };</div><div class="line"><a name="l00138"></a><span class="lineno"> 138</span> </div><div class="line"><a name="l00139"></a><span class="lineno"> 139</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00140"></a><span class="lineno"> 140</span>  <span class="keyword">struct </span>_Has_addressof_mem<_Tp,</div><div class="line"><a name="l00141"></a><span class="lineno"> 141</span>  __void_t<decltype( <a class="code" href="a01538.html">std</a>::declval<const _Tp&>().operator&() )></div><div class="line"><a name="l00142"></a><span class="lineno"> 142</span>  ></div><div class="line"><a name="l00143"></a><span class="lineno"> 143</span>  : <a class="code" href="a03040.html">std::true_type</a> { };</div><div class="line"><a name="l00144"></a><span class="lineno"> 144</span> </div><div class="line"><a name="l00145"></a><span class="lineno"> 145</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp, <span class="keyword">typename</span> = <span class="keywordtype">void</span>></div><div class="line"><a name="l00146"></a><span class="lineno"> 146</span>  <span class="keyword">struct </span>_Has_addressof_free : <a class="code" href="a03040.html">std::false_type</a> { };</div><div class="line"><a name="l00147"></a><span class="lineno"> 147</span> </div><div class="line"><a name="l00148"></a><span class="lineno"> 148</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00149"></a><span class="lineno"> 149</span>  <span class="keyword">struct </span>_Has_addressof_free<_Tp,</div><div class="line"><a name="l00150"></a><span class="lineno"> 150</span>  __void_t<decltype( operator&(std::declval<const _Tp&>()) )></div><div class="line"><a name="l00151"></a><span class="lineno"> 151</span>  ></div><div class="line"><a name="l00152"></a><span class="lineno"> 152</span>  : <a class="code" href="a03040.html">std::true_type</a> { };</div><div class="line"><a name="l00153"></a><span class="lineno"> 153</span> <span class="comment"></span></div><div class="line"><a name="l00154"></a><span class="lineno"> 154</span> <span class="comment"> /**</span></div><div class="line"><a name="l00155"></a><span class="lineno"> 155</span> <span class="comment"> * @brief Trait that detects the presence of an overloaded unary operator&.</span></div><div class="line"><a name="l00156"></a><span class="lineno"> 156</span> <span class="comment"> *</span></div><div class="line"><a name="l00157"></a><span class="lineno"> 157</span> <span class="comment"> * Practically speaking this detects the presence of such an operator when</span></div><div class="line"><a name="l00158"></a><span class="lineno"> 158</span> <span class="comment"> * called on a const-qualified lvalue (e.g.</span></div><div class="line"><a name="l00159"></a><span class="lineno"> 159</span> <span class="comment"> * declval<const _Tp&>().operator&()).</span></div><div class="line"><a name="l00160"></a><span class="lineno"> 160</span> <span class="comment"> */</span></div><div class="line"><a name="l00161"></a><span class="lineno"> 161</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00162"></a><span class="lineno"><a class="line" href="a10020.html"> 162</a></span>  <span class="keyword">struct </span><a class="code" href="a10020.html">_Has_addressof</a></div><div class="line"><a name="l00163"></a><span class="lineno"> 163</span>  : std::__or_<_Has_addressof_mem<_Tp>, _Has_addressof_free<_Tp>>::type</div><div class="line"><a name="l00164"></a><span class="lineno"> 164</span>  { };</div><div class="line"><a name="l00165"></a><span class="lineno"> 165</span> <span class="comment"></span></div><div class="line"><a name="l00166"></a><span class="lineno"> 166</span> <span class="comment"> /**</span></div><div class="line"><a name="l00167"></a><span class="lineno"> 167</span> <span class="comment"> * @brief An overload that attempts to take the address of an lvalue as a</span></div><div class="line"><a name="l00168"></a><span class="lineno"> 168</span> <span class="comment"> * constant expression. Falls back to __addressof in the presence of an</span></div><div class="line"><a name="l00169"></a><span class="lineno"> 169</span> <span class="comment"> * overloaded addressof operator (unary operator&), in which case the call</span></div><div class="line"><a name="l00170"></a><span class="lineno"> 170</span> <span class="comment"> * will not be a constant expression.</span></div><div class="line"><a name="l00171"></a><span class="lineno"> 171</span> <span class="comment"> */</span></div><div class="line"><a name="l00172"></a><span class="lineno"> 172</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00173"></a><span class="lineno"> 173</span>  constexpr</div><div class="line"><a name="l00174"></a><span class="lineno"> 174</span>  <a class="code" href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">enable_if_t<!_Has_addressof<_Tp>::value</a>, _Tp*></div><div class="line"><a name="l00175"></a><span class="lineno"><a class="line" href="a01515.html#gaec6098e9e49d3b1918c5de29086aeead"> 175</a></span>  <a class="code" href="a01515.html#gaec6098e9e49d3b1918c5de29086aeead">__constexpr_addressof</a>(_Tp& __t)</div><div class="line"><a name="l00176"></a><span class="lineno"> 176</span>  { <span class="keywordflow">return</span> &__t; }</div><div class="line"><a name="l00177"></a><span class="lineno"> 177</span> <span class="comment"></span></div><div class="line"><a name="l00178"></a><span class="lineno"> 178</span> <span class="comment"> /**</span></div><div class="line"><a name="l00179"></a><span class="lineno"> 179</span> <span class="comment"> * @brief Fallback overload that defers to __addressof.</span></div><div class="line"><a name="l00180"></a><span class="lineno"> 180</span> <span class="comment"> */</span></div><div class="line"><a name="l00181"></a><span class="lineno"> 181</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00182"></a><span class="lineno"> 182</span>  <span class="keyword">inline</span></div><div class="line"><a name="l00183"></a><span class="lineno"> 183</span>  <a class="code" href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">enable_if_t<_Has_addressof<_Tp>::value</a>, _Tp*></div><div class="line"><a name="l00184"></a><span class="lineno"><a class="line" href="a01007.html#gaec6098e9e49d3b1918c5de29086aeead"> 184</a></span>  <a class="code" href="a01515.html#gaec6098e9e49d3b1918c5de29086aeead">__constexpr_addressof</a>(_Tp& __t)</div><div class="line"><a name="l00185"></a><span class="lineno"> 185</span>  { <span class="keywordflow">return</span> <a class="code" href="a01477.html#ga1954d5552e24586051011312041033f6">std::__addressof</a>(__t); }</div><div class="line"><a name="l00186"></a><span class="lineno"> 186</span> <span class="preprocessor">#endif // __cpp_lib_addressof_constexpr</span></div><div class="line"><a name="l00187"></a><span class="lineno"> 187</span> <span class="comment"></span></div><div class="line"><a name="l00188"></a><span class="lineno"> 188</span> <span class="comment"> /**</span></div><div class="line"><a name="l00189"></a><span class="lineno"> 189</span> <span class="comment"> * @brief Class template that holds the necessary state for @ref optional</span></div><div class="line"><a name="l00190"></a><span class="lineno"> 190</span> <span class="comment"> * and that has the responsibility for construction and the special members.</span></div><div class="line"><a name="l00191"></a><span class="lineno"> 191</span> <span class="comment"> *</span></div><div class="line"><a name="l00192"></a><span class="lineno"> 192</span> <span class="comment"> * Such a separate base class template is necessary in order to</span></div><div class="line"><a name="l00193"></a><span class="lineno"> 193</span> <span class="comment"> * conditionally enable the special members (e.g. copy/move constructors).</span></div><div class="line"><a name="l00194"></a><span class="lineno"> 194</span> <span class="comment"> * Note that this means that @ref _Optional_base implements the</span></div><div class="line"><a name="l00195"></a><span class="lineno"> 195</span> <span class="comment"> * functionality for copy and move assignment, but not for converting</span></div><div class="line"><a name="l00196"></a><span class="lineno"> 196</span> <span class="comment"> * assignment.</span></div><div class="line"><a name="l00197"></a><span class="lineno"> 197</span> <span class="comment"> *</span></div><div class="line"><a name="l00198"></a><span class="lineno"> 198</span> <span class="comment"> * @see optional, _Enable_special_members</span></div><div class="line"><a name="l00199"></a><span class="lineno"> 199</span> <span class="comment"> */</span></div><div class="line"><a name="l00200"></a><span class="lineno"> 200</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp, <span class="keywordtype">bool</span> _ShouldProvideDestructor =</div><div class="line"><a name="l00201"></a><span class="lineno"> 201</span>  !<a class="code" href="a03848.html">is_trivially_destructible<_Tp>::value</a>></div><div class="line"><a name="l00202"></a><span class="lineno"><a class="line" href="a10024.html"> 202</a></span>  <span class="keyword">class </span><a class="code" href="a10024.html">_Optional_base</a></div><div class="line"><a name="l00203"></a><span class="lineno"> 203</span>  {</div><div class="line"><a name="l00204"></a><span class="lineno"> 204</span>  <span class="keyword">private</span>:</div><div class="line"><a name="l00205"></a><span class="lineno"> 205</span>  <span class="comment">// Remove const to avoid prohibition of reusing object storage for</span></div><div class="line"><a name="l00206"></a><span class="lineno"> 206</span>  <span class="comment">// const-qualified types in [3.8/9]. This is strictly internal</span></div><div class="line"><a name="l00207"></a><span class="lineno"> 207</span>  <span class="comment">// and even optional itself is oblivious to it.</span></div><div class="line"><a name="l00208"></a><span class="lineno"> 208</span>  <span class="keyword">using</span> _Stored_type = <a class="code" href="a01476.html#ga4e79124b56e4ce8037d87387898b9d1f">remove_const_t<_Tp></a>;</div><div class="line"><a name="l00209"></a><span class="lineno"> 209</span> </div><div class="line"><a name="l00210"></a><span class="lineno"> 210</span>  <span class="keyword">public</span>:</div><div class="line"><a name="l00211"></a><span class="lineno"> 211</span>  <span class="comment">// [X.Y.4.1] Constructors.</span></div><div class="line"><a name="l00212"></a><span class="lineno"> 212</span> </div><div class="line"><a name="l00213"></a><span class="lineno"> 213</span>  <span class="comment">// Constructors for disengaged optionals.</span></div><div class="line"><a name="l00214"></a><span class="lineno"> 214</span>  constexpr <a class="code" href="a10024.html">_Optional_base</a>() noexcept</div><div class="line"><a name="l00215"></a><span class="lineno"> 215</span>  : _M_empty{} { }</div><div class="line"><a name="l00216"></a><span class="lineno"> 216</span> </div><div class="line"><a name="l00217"></a><span class="lineno"> 217</span>  constexpr <a class="code" href="a10024.html">_Optional_base</a>(<a class="code" href="a09996.html">nullopt_t</a>) noexcept</div><div class="line"><a name="l00218"></a><span class="lineno"> 218</span>  : <a class="code" href="a10024.html">_Optional_base</a>{} { }</div><div class="line"><a name="l00219"></a><span class="lineno"> 219</span> </div><div class="line"><a name="l00220"></a><span class="lineno"> 220</span>  <span class="comment">// Constructors for engaged optionals.</span></div><div class="line"><a name="l00221"></a><span class="lineno"> 221</span>  <span class="keyword">template</span><<span class="keyword">typename</span>... _Args></div><div class="line"><a name="l00222"></a><span class="lineno"> 222</span>  constexpr <span class="keyword">explicit</span> <a class="code" href="a10024.html">_Optional_base</a>(<a class="code" href="a09992.html">in_place_t</a>, _Args&&... __args)</div><div class="line"><a name="l00223"></a><span class="lineno"> 223</span>  : _M_payload(std::forward<_Args>(__args)...), _M_engaged(<span class="keyword">true</span>) { }</div><div class="line"><a name="l00224"></a><span class="lineno"> 224</span> </div><div class="line"><a name="l00225"></a><span class="lineno"> 225</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Up, <span class="keyword">typename</span>... _Args,</div><div class="line"><a name="l00226"></a><span class="lineno"> 226</span>  <a class="code" href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">enable_if_t</a><<a class="code" href="a03572.html">is_constructible</a><_Tp,</div><div class="line"><a name="l00227"></a><span class="lineno"> 227</span>  <a class="code" href="a01652.html">initializer_list<_Up></a>&,</div><div class="line"><a name="l00228"></a><span class="lineno"> 228</span>  _Args&&...>::value,</div><div class="line"><a name="l00229"></a><span class="lineno"> 229</span>  <span class="keywordtype">int</span>>...></div><div class="line"><a name="l00230"></a><span class="lineno"> 230</span>  constexpr <span class="keyword">explicit</span> <a class="code" href="a10024.html">_Optional_base</a>(<a class="code" href="a09992.html">in_place_t</a>,</div><div class="line"><a name="l00231"></a><span class="lineno"> 231</span>  <a class="code" href="a01652.html">initializer_list<_Up></a> __il,</div><div class="line"><a name="l00232"></a><span class="lineno"> 232</span>  _Args&&... __args)</div><div class="line"><a name="l00233"></a><span class="lineno"> 233</span>  : _M_payload(__il, std::forward<_Args>(__args)...),</div><div class="line"><a name="l00234"></a><span class="lineno"> 234</span>  _M_engaged(<span class="keyword">true</span>) { }</div><div class="line"><a name="l00235"></a><span class="lineno"> 235</span> </div><div class="line"><a name="l00236"></a><span class="lineno"> 236</span>  <span class="comment">// Copy and move constructors.</span></div><div class="line"><a name="l00237"></a><span class="lineno"> 237</span>  <a class="code" href="a10024.html">_Optional_base</a>(<span class="keyword">const</span> <a class="code" href="a10024.html">_Optional_base</a>& __other)</div><div class="line"><a name="l00238"></a><span class="lineno"> 238</span>  {</div><div class="line"><a name="l00239"></a><span class="lineno"> 239</span>  <span class="keywordflow">if</span> (__other._M_engaged)</div><div class="line"><a name="l00240"></a><span class="lineno"> 240</span>  this->_M_construct(__other._M_get());</div><div class="line"><a name="l00241"></a><span class="lineno"> 241</span>  }</div><div class="line"><a name="l00242"></a><span class="lineno"> 242</span> </div><div class="line"><a name="l00243"></a><span class="lineno"> 243</span>  <a class="code" href="a10024.html">_Optional_base</a>(<a class="code" href="a10024.html">_Optional_base</a>&& __other)</div><div class="line"><a name="l00244"></a><span class="lineno"> 244</span>  noexcept(<a class="code" href="a03676.html">is_nothrow_move_constructible<_Tp></a>())</div><div class="line"><a name="l00245"></a><span class="lineno"> 245</span>  {</div><div class="line"><a name="l00246"></a><span class="lineno"> 246</span>  <span class="keywordflow">if</span> (__other._M_engaged)</div><div class="line"><a name="l00247"></a><span class="lineno"> 247</span>  this->_M_construct(std::move(__other._M_get()));</div><div class="line"><a name="l00248"></a><span class="lineno"> 248</span>  }</div><div class="line"><a name="l00249"></a><span class="lineno"> 249</span> </div><div class="line"><a name="l00250"></a><span class="lineno"> 250</span>  <span class="comment">// [X.Y.4.3] (partly) Assignment.</span></div><div class="line"><a name="l00251"></a><span class="lineno"> 251</span>  <a class="code" href="a10024.html">_Optional_base</a>&</div><div class="line"><a name="l00252"></a><span class="lineno"> 252</span>  operator=(<span class="keyword">const</span> <a class="code" href="a10024.html">_Optional_base</a>& __other)</div><div class="line"><a name="l00253"></a><span class="lineno"> 253</span>  {</div><div class="line"><a name="l00254"></a><span class="lineno"> 254</span>  <span class="keywordflow">if</span> (this->_M_engaged && __other._M_engaged)</div><div class="line"><a name="l00255"></a><span class="lineno"> 255</span>  this->_M_get() = __other._M_get();</div><div class="line"><a name="l00256"></a><span class="lineno"> 256</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00257"></a><span class="lineno"> 257</span>  {</div><div class="line"><a name="l00258"></a><span class="lineno"> 258</span>  <span class="keywordflow">if</span> (__other._M_engaged)</div><div class="line"><a name="l00259"></a><span class="lineno"> 259</span>  this->_M_construct(__other._M_get());</div><div class="line"><a name="l00260"></a><span class="lineno"> 260</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00261"></a><span class="lineno"> 261</span>  this->_M_reset();</div><div class="line"><a name="l00262"></a><span class="lineno"> 262</span>  }</div><div class="line"><a name="l00263"></a><span class="lineno"> 263</span> </div><div class="line"><a name="l00264"></a><span class="lineno"> 264</span>  <span class="keywordflow">return</span> *<span class="keyword">this</span>;</div><div class="line"><a name="l00265"></a><span class="lineno"> 265</span>  }</div><div class="line"><a name="l00266"></a><span class="lineno"> 266</span> </div><div class="line"><a name="l00267"></a><span class="lineno"> 267</span>  <a class="code" href="a10024.html">_Optional_base</a>&</div><div class="line"><a name="l00268"></a><span class="lineno"> 268</span>  operator=(<a class="code" href="a10024.html">_Optional_base</a>&& __other)</div><div class="line"><a name="l00269"></a><span class="lineno"> 269</span>  noexcept(__and_<<a class="code" href="a03676.html">is_nothrow_move_constructible<_Tp></a>,</div><div class="line"><a name="l00270"></a><span class="lineno"> 270</span>  <a class="code" href="a03752.html">is_nothrow_move_assignable<_Tp></a>>())</div><div class="line"><a name="l00271"></a><span class="lineno"> 271</span>  {</div><div class="line"><a name="l00272"></a><span class="lineno"> 272</span>  <span class="keywordflow">if</span> (this->_M_engaged && __other._M_engaged)</div><div class="line"><a name="l00273"></a><span class="lineno"> 273</span>  this->_M_get() = std::move(__other._M_get());</div><div class="line"><a name="l00274"></a><span class="lineno"> 274</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00275"></a><span class="lineno"> 275</span>  {</div><div class="line"><a name="l00276"></a><span class="lineno"> 276</span>  <span class="keywordflow">if</span> (__other._M_engaged)</div><div class="line"><a name="l00277"></a><span class="lineno"> 277</span>  this->_M_construct(std::move(__other._M_get()));</div><div class="line"><a name="l00278"></a><span class="lineno"> 278</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00279"></a><span class="lineno"> 279</span>  this->_M_reset();</div><div class="line"><a name="l00280"></a><span class="lineno"> 280</span>  }</div><div class="line"><a name="l00281"></a><span class="lineno"> 281</span>  <span class="keywordflow">return</span> *<span class="keyword">this</span>;</div><div class="line"><a name="l00282"></a><span class="lineno"> 282</span>  }</div><div class="line"><a name="l00283"></a><span class="lineno"> 283</span> </div><div class="line"><a name="l00284"></a><span class="lineno"> 284</span>  <span class="comment">// [X.Y.4.2] Destructor.</span></div><div class="line"><a name="l00285"></a><span class="lineno"> 285</span>  ~<a class="code" href="a10024.html">_Optional_base</a>()</div><div class="line"><a name="l00286"></a><span class="lineno"> 286</span>  {</div><div class="line"><a name="l00287"></a><span class="lineno"> 287</span>  <span class="keywordflow">if</span> (this->_M_engaged)</div><div class="line"><a name="l00288"></a><span class="lineno"> 288</span>  this->_M_payload.~_Stored_type();</div><div class="line"><a name="l00289"></a><span class="lineno"> 289</span>  }</div><div class="line"><a name="l00290"></a><span class="lineno"> 290</span> </div><div class="line"><a name="l00291"></a><span class="lineno"> 291</span>  <span class="comment">// The following functionality is also needed by optional, hence the</span></div><div class="line"><a name="l00292"></a><span class="lineno"> 292</span>  <span class="comment">// protected accessibility.</span></div><div class="line"><a name="l00293"></a><span class="lineno"> 293</span>  <span class="keyword">protected</span>:</div><div class="line"><a name="l00294"></a><span class="lineno"> 294</span>  constexpr <span class="keywordtype">bool</span> _M_is_engaged() <span class="keyword">const</span> noexcept</div><div class="line"><a name="l00295"></a><span class="lineno"> 295</span>  { <span class="keywordflow">return</span> this->_M_engaged; }</div><div class="line"><a name="l00296"></a><span class="lineno"> 296</span> </div><div class="line"><a name="l00297"></a><span class="lineno"> 297</span>  <span class="comment">// The _M_get operations have _M_engaged as a precondition.</span></div><div class="line"><a name="l00298"></a><span class="lineno"> 298</span>  constexpr _Tp&</div><div class="line"><a name="l00299"></a><span class="lineno"> 299</span>  _M_get() noexcept</div><div class="line"><a name="l00300"></a><span class="lineno"> 300</span>  { <span class="keywordflow">return</span> _M_payload; }</div><div class="line"><a name="l00301"></a><span class="lineno"> 301</span> </div><div class="line"><a name="l00302"></a><span class="lineno"> 302</span>  constexpr <span class="keyword">const</span> _Tp&</div><div class="line"><a name="l00303"></a><span class="lineno"> 303</span>  _M_get() <span class="keyword">const</span> noexcept</div><div class="line"><a name="l00304"></a><span class="lineno"> 304</span>  { <span class="keywordflow">return</span> _M_payload; }</div><div class="line"><a name="l00305"></a><span class="lineno"> 305</span> </div><div class="line"><a name="l00306"></a><span class="lineno"> 306</span>  <span class="comment">// The _M_construct operation has !_M_engaged as a precondition</span></div><div class="line"><a name="l00307"></a><span class="lineno"> 307</span>  <span class="comment">// while _M_destruct has _M_engaged as a precondition.</span></div><div class="line"><a name="l00308"></a><span class="lineno"> 308</span>  <span class="keyword">template</span><<span class="keyword">typename</span>... _Args></div><div class="line"><a name="l00309"></a><span class="lineno"> 309</span>  <span class="keywordtype">void</span></div><div class="line"><a name="l00310"></a><span class="lineno"> 310</span>  _M_construct(_Args&&... __args)</div><div class="line"><a name="l00311"></a><span class="lineno"> 311</span>  noexcept(<a class="code" href="a03644.html">is_nothrow_constructible<_Stored_type, _Args...></a>())</div><div class="line"><a name="l00312"></a><span class="lineno"> 312</span>  {</div><div class="line"><a name="l00313"></a><span class="lineno"> 313</span>  ::new (<a class="code" href="a01477.html#ga1954d5552e24586051011312041033f6">std::__addressof</a>(this->_M_payload))</div><div class="line"><a name="l00314"></a><span class="lineno"> 314</span>  _Stored_type(std::forward<_Args>(__args)...);</div><div class="line"><a name="l00315"></a><span class="lineno"> 315</span>  this->_M_engaged = <span class="keyword">true</span>;</div><div class="line"><a name="l00316"></a><span class="lineno"> 316</span>  }</div><div class="line"><a name="l00317"></a><span class="lineno"> 317</span> </div><div class="line"><a name="l00318"></a><span class="lineno"> 318</span>  <span class="keywordtype">void</span></div><div class="line"><a name="l00319"></a><span class="lineno"> 319</span>  _M_destruct()</div><div class="line"><a name="l00320"></a><span class="lineno"> 320</span>  {</div><div class="line"><a name="l00321"></a><span class="lineno"> 321</span>  this->_M_engaged = <span class="keyword">false</span>;</div><div class="line"><a name="l00322"></a><span class="lineno"> 322</span>  this->_M_payload.~_Stored_type();</div><div class="line"><a name="l00323"></a><span class="lineno"> 323</span>  }</div><div class="line"><a name="l00324"></a><span class="lineno"> 324</span> </div><div class="line"><a name="l00325"></a><span class="lineno"> 325</span>  <span class="comment">// _M_reset is a 'safe' operation with no precondition.</span></div><div class="line"><a name="l00326"></a><span class="lineno"> 326</span>  <span class="keywordtype">void</span></div><div class="line"><a name="l00327"></a><span class="lineno"> 327</span>  _M_reset()</div><div class="line"><a name="l00328"></a><span class="lineno"> 328</span>  {</div><div class="line"><a name="l00329"></a><span class="lineno"> 329</span>  <span class="keywordflow">if</span> (this->_M_engaged)</div><div class="line"><a name="l00330"></a><span class="lineno"> 330</span>  this->_M_destruct();</div><div class="line"><a name="l00331"></a><span class="lineno"> 331</span>  }</div><div class="line"><a name="l00332"></a><span class="lineno"> 332</span> </div><div class="line"><a name="l00333"></a><span class="lineno"> 333</span>  <span class="keyword">private</span>:</div><div class="line"><a name="l00334"></a><span class="lineno"> 334</span>  <span class="keyword">struct </span>_Empty_byte { };</div><div class="line"><a name="l00335"></a><span class="lineno"> 335</span>  <span class="keyword">union </span>{</div><div class="line"><a name="l00336"></a><span class="lineno"> 336</span>  _Empty_byte _M_empty;</div><div class="line"><a name="l00337"></a><span class="lineno"> 337</span>  _Stored_type _M_payload;</div><div class="line"><a name="l00338"></a><span class="lineno"> 338</span>  };</div><div class="line"><a name="l00339"></a><span class="lineno"> 339</span>  <span class="keywordtype">bool</span> _M_engaged = <span class="keyword">false</span>;</div><div class="line"><a name="l00340"></a><span class="lineno"> 340</span>  };</div><div class="line"><a name="l00341"></a><span class="lineno"> 341</span> <span class="comment"></span></div><div class="line"><a name="l00342"></a><span class="lineno"> 342</span> <span class="comment"> /// Partial specialization that is exactly identical to the primary template</span></div><div class="line"><a name="l00343"></a><span class="lineno"> 343</span> <span class="comment"> /// save for not providing a destructor, to fulfill triviality requirements.</span></div><div class="line"><a name="l00344"></a><span class="lineno"> 344</span> <span class="comment"></span> <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00345"></a><span class="lineno"><a class="line" href="a10036.html"> 345</a></span>  <span class="keyword">class </span><a class="code" href="a10024.html">_Optional_base</a><_Tp, false></div><div class="line"><a name="l00346"></a><span class="lineno"> 346</span>  {</div><div class="line"><a name="l00347"></a><span class="lineno"> 347</span>  <span class="keyword">private</span>:</div><div class="line"><a name="l00348"></a><span class="lineno"> 348</span>  <span class="keyword">using</span> _Stored_type = <a class="code" href="a01476.html#ga4e79124b56e4ce8037d87387898b9d1f">remove_const_t<_Tp></a>;</div><div class="line"><a name="l00349"></a><span class="lineno"> 349</span> </div><div class="line"><a name="l00350"></a><span class="lineno"> 350</span>  <span class="keyword">public</span>:</div><div class="line"><a name="l00351"></a><span class="lineno"> 351</span>  constexpr <a class="code" href="a10024.html">_Optional_base</a>() noexcept</div><div class="line"><a name="l00352"></a><span class="lineno"> 352</span>  : _M_empty{} { }</div><div class="line"><a name="l00353"></a><span class="lineno"> 353</span> </div><div class="line"><a name="l00354"></a><span class="lineno"> 354</span>  constexpr <a class="code" href="a10024.html">_Optional_base</a>(<a class="code" href="a09996.html">nullopt_t</a>) noexcept</div><div class="line"><a name="l00355"></a><span class="lineno"> 355</span>  : <a class="code" href="a10024.html">_Optional_base</a>{} { }</div><div class="line"><a name="l00356"></a><span class="lineno"> 356</span> </div><div class="line"><a name="l00357"></a><span class="lineno"> 357</span>  <span class="keyword">template</span><<span class="keyword">typename</span>... _Args></div><div class="line"><a name="l00358"></a><span class="lineno"> 358</span>  constexpr <span class="keyword">explicit</span> <a class="code" href="a10024.html">_Optional_base</a>(<a class="code" href="a09992.html">in_place_t</a>, _Args&&... __args)</div><div class="line"><a name="l00359"></a><span class="lineno"> 359</span>  : _M_payload(std::forward<_Args>(__args)...), _M_engaged(<span class="keyword">true</span>) { }</div><div class="line"><a name="l00360"></a><span class="lineno"> 360</span> </div><div class="line"><a name="l00361"></a><span class="lineno"> 361</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Up, <span class="keyword">typename</span>... _Args,</div><div class="line"><a name="l00362"></a><span class="lineno"> 362</span>  <a class="code" href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">enable_if_t</a><<a class="code" href="a03572.html">is_constructible</a><_Tp,</div><div class="line"><a name="l00363"></a><span class="lineno"> 363</span>  <a class="code" href="a01652.html">initializer_list<_Up></a>&,</div><div class="line"><a name="l00364"></a><span class="lineno"> 364</span>  _Args&&...>::value,</div><div class="line"><a name="l00365"></a><span class="lineno"> 365</span>  <span class="keywordtype">int</span>>...></div><div class="line"><a name="l00366"></a><span class="lineno"> 366</span>  constexpr <span class="keyword">explicit</span> <a class="code" href="a10024.html">_Optional_base</a>(<a class="code" href="a09992.html">in_place_t</a>,</div><div class="line"><a name="l00367"></a><span class="lineno"> 367</span>  <a class="code" href="a01652.html">initializer_list<_Up></a> __il,</div><div class="line"><a name="l00368"></a><span class="lineno"> 368</span>  _Args&&... __args)</div><div class="line"><a name="l00369"></a><span class="lineno"> 369</span>  : _M_payload(__il, std::forward<_Args>(__args)...),</div><div class="line"><a name="l00370"></a><span class="lineno"> 370</span>  _M_engaged(<span class="keyword">true</span>) { }</div><div class="line"><a name="l00371"></a><span class="lineno"> 371</span> </div><div class="line"><a name="l00372"></a><span class="lineno"> 372</span>  <a class="code" href="a10024.html">_Optional_base</a>(<span class="keyword">const</span> <a class="code" href="a10024.html">_Optional_base</a>& __other)</div><div class="line"><a name="l00373"></a><span class="lineno"> 373</span>  {</div><div class="line"><a name="l00374"></a><span class="lineno"> 374</span>  <span class="keywordflow">if</span> (__other._M_engaged)</div><div class="line"><a name="l00375"></a><span class="lineno"> 375</span>  this->_M_construct(__other._M_get());</div><div class="line"><a name="l00376"></a><span class="lineno"> 376</span>  }</div><div class="line"><a name="l00377"></a><span class="lineno"> 377</span> </div><div class="line"><a name="l00378"></a><span class="lineno"> 378</span>  <a class="code" href="a10024.html">_Optional_base</a>(<a class="code" href="a10024.html">_Optional_base</a>&& __other)</div><div class="line"><a name="l00379"></a><span class="lineno"> 379</span>  noexcept(<a class="code" href="a03676.html">is_nothrow_move_constructible<_Tp></a>())</div><div class="line"><a name="l00380"></a><span class="lineno"> 380</span>  {</div><div class="line"><a name="l00381"></a><span class="lineno"> 381</span>  <span class="keywordflow">if</span> (__other._M_engaged)</div><div class="line"><a name="l00382"></a><span class="lineno"> 382</span>  this->_M_construct(std::move(__other._M_get()));</div><div class="line"><a name="l00383"></a><span class="lineno"> 383</span>  }</div><div class="line"><a name="l00384"></a><span class="lineno"> 384</span> </div><div class="line"><a name="l00385"></a><span class="lineno"> 385</span>  <a class="code" href="a10024.html">_Optional_base</a>&</div><div class="line"><a name="l00386"></a><span class="lineno"> 386</span>  operator=(<span class="keyword">const</span> <a class="code" href="a10024.html">_Optional_base</a>& __other)</div><div class="line"><a name="l00387"></a><span class="lineno"> 387</span>  {</div><div class="line"><a name="l00388"></a><span class="lineno"> 388</span>  <span class="keywordflow">if</span> (this->_M_engaged && __other._M_engaged)</div><div class="line"><a name="l00389"></a><span class="lineno"> 389</span>  this->_M_get() = __other._M_get();</div><div class="line"><a name="l00390"></a><span class="lineno"> 390</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00391"></a><span class="lineno"> 391</span>  {</div><div class="line"><a name="l00392"></a><span class="lineno"> 392</span>  <span class="keywordflow">if</span> (__other._M_engaged)</div><div class="line"><a name="l00393"></a><span class="lineno"> 393</span>  this->_M_construct(__other._M_get());</div><div class="line"><a name="l00394"></a><span class="lineno"> 394</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00395"></a><span class="lineno"> 395</span>  this->_M_reset();</div><div class="line"><a name="l00396"></a><span class="lineno"> 396</span>  }</div><div class="line"><a name="l00397"></a><span class="lineno"> 397</span>  <span class="keywordflow">return</span> *<span class="keyword">this</span>;</div><div class="line"><a name="l00398"></a><span class="lineno"> 398</span>  }</div><div class="line"><a name="l00399"></a><span class="lineno"> 399</span> </div><div class="line"><a name="l00400"></a><span class="lineno"> 400</span>  <a class="code" href="a10024.html">_Optional_base</a>&</div><div class="line"><a name="l00401"></a><span class="lineno"> 401</span>  operator=(<a class="code" href="a10024.html">_Optional_base</a>&& __other)</div><div class="line"><a name="l00402"></a><span class="lineno"> 402</span>  noexcept(__and_<<a class="code" href="a03676.html">is_nothrow_move_constructible<_Tp></a>,</div><div class="line"><a name="l00403"></a><span class="lineno"> 403</span>  <a class="code" href="a03752.html">is_nothrow_move_assignable<_Tp></a>>())</div><div class="line"><a name="l00404"></a><span class="lineno"> 404</span>  {</div><div class="line"><a name="l00405"></a><span class="lineno"> 405</span>  <span class="keywordflow">if</span> (this->_M_engaged && __other._M_engaged)</div><div class="line"><a name="l00406"></a><span class="lineno"> 406</span>  this->_M_get() = std::move(__other._M_get());</div><div class="line"><a name="l00407"></a><span class="lineno"> 407</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00408"></a><span class="lineno"> 408</span>  {</div><div class="line"><a name="l00409"></a><span class="lineno"> 409</span>  <span class="keywordflow">if</span> (__other._M_engaged)</div><div class="line"><a name="l00410"></a><span class="lineno"> 410</span>  this->_M_construct(std::move(__other._M_get()));</div><div class="line"><a name="l00411"></a><span class="lineno"> 411</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00412"></a><span class="lineno"> 412</span>  this->_M_reset();</div><div class="line"><a name="l00413"></a><span class="lineno"> 413</span>  }</div><div class="line"><a name="l00414"></a><span class="lineno"> 414</span>  <span class="keywordflow">return</span> *<span class="keyword">this</span>;</div><div class="line"><a name="l00415"></a><span class="lineno"> 415</span>  }</div><div class="line"><a name="l00416"></a><span class="lineno"> 416</span> </div><div class="line"><a name="l00417"></a><span class="lineno"> 417</span>  <span class="comment">// Sole difference</span></div><div class="line"><a name="l00418"></a><span class="lineno"> 418</span>  <span class="comment">// ~_Optional_base() noexcept = default;</span></div><div class="line"><a name="l00419"></a><span class="lineno"> 419</span> </div><div class="line"><a name="l00420"></a><span class="lineno"> 420</span>  <span class="keyword">protected</span>:</div><div class="line"><a name="l00421"></a><span class="lineno"> 421</span>  constexpr <span class="keywordtype">bool</span> _M_is_engaged() <span class="keyword">const</span> noexcept</div><div class="line"><a name="l00422"></a><span class="lineno"> 422</span>  { <span class="keywordflow">return</span> this->_M_engaged; }</div><div class="line"><a name="l00423"></a><span class="lineno"> 423</span> </div><div class="line"><a name="l00424"></a><span class="lineno"> 424</span>  _Tp&</div><div class="line"><a name="l00425"></a><span class="lineno"> 425</span>  _M_get() noexcept</div><div class="line"><a name="l00426"></a><span class="lineno"> 426</span>  { <span class="keywordflow">return</span> _M_payload; }</div><div class="line"><a name="l00427"></a><span class="lineno"> 427</span> </div><div class="line"><a name="l00428"></a><span class="lineno"> 428</span>  constexpr <span class="keyword">const</span> _Tp&</div><div class="line"><a name="l00429"></a><span class="lineno"> 429</span>  _M_get() <span class="keyword">const</span> noexcept</div><div class="line"><a name="l00430"></a><span class="lineno"> 430</span>  { <span class="keywordflow">return</span> _M_payload; }</div><div class="line"><a name="l00431"></a><span class="lineno"> 431</span> </div><div class="line"><a name="l00432"></a><span class="lineno"> 432</span>  <span class="keyword">template</span><<span class="keyword">typename</span>... _Args></div><div class="line"><a name="l00433"></a><span class="lineno"> 433</span>  <span class="keywordtype">void</span></div><div class="line"><a name="l00434"></a><span class="lineno"> 434</span>  _M_construct(_Args&&... __args)</div><div class="line"><a name="l00435"></a><span class="lineno"> 435</span>  noexcept(<a class="code" href="a03644.html">is_nothrow_constructible<_Stored_type, _Args...></a>())</div><div class="line"><a name="l00436"></a><span class="lineno"> 436</span>  {</div><div class="line"><a name="l00437"></a><span class="lineno"> 437</span>  ::new (<a class="code" href="a01477.html#ga1954d5552e24586051011312041033f6">std::__addressof</a>(this->_M_payload))</div><div class="line"><a name="l00438"></a><span class="lineno"> 438</span>  _Stored_type(std::forward<_Args>(__args)...);</div><div class="line"><a name="l00439"></a><span class="lineno"> 439</span>  this->_M_engaged = <span class="keyword">true</span>;</div><div class="line"><a name="l00440"></a><span class="lineno"> 440</span>  }</div><div class="line"><a name="l00441"></a><span class="lineno"> 441</span> </div><div class="line"><a name="l00442"></a><span class="lineno"> 442</span>  <span class="keywordtype">void</span></div><div class="line"><a name="l00443"></a><span class="lineno"> 443</span>  _M_destruct()</div><div class="line"><a name="l00444"></a><span class="lineno"> 444</span>  {</div><div class="line"><a name="l00445"></a><span class="lineno"> 445</span>  this->_M_engaged = <span class="keyword">false</span>;</div><div class="line"><a name="l00446"></a><span class="lineno"> 446</span>  this->_M_payload.~_Stored_type();</div><div class="line"><a name="l00447"></a><span class="lineno"> 447</span>  }</div><div class="line"><a name="l00448"></a><span class="lineno"> 448</span> </div><div class="line"><a name="l00449"></a><span class="lineno"> 449</span>  <span class="keywordtype">void</span></div><div class="line"><a name="l00450"></a><span class="lineno"> 450</span>  _M_reset()</div><div class="line"><a name="l00451"></a><span class="lineno"> 451</span>  {</div><div class="line"><a name="l00452"></a><span class="lineno"> 452</span>  <span class="keywordflow">if</span> (this->_M_engaged)</div><div class="line"><a name="l00453"></a><span class="lineno"> 453</span>  this->_M_destruct();</div><div class="line"><a name="l00454"></a><span class="lineno"> 454</span>  }</div><div class="line"><a name="l00455"></a><span class="lineno"> 455</span> </div><div class="line"><a name="l00456"></a><span class="lineno"> 456</span>  <span class="keyword">private</span>:</div><div class="line"><a name="l00457"></a><span class="lineno"> 457</span>  <span class="keyword">struct </span>_Empty_byte { };</div><div class="line"><a name="l00458"></a><span class="lineno"> 458</span>  <span class="keyword">union</span></div><div class="line"><a name="l00459"></a><span class="lineno"> 459</span>  {</div><div class="line"><a name="l00460"></a><span class="lineno"> 460</span>  _Empty_byte _M_empty;</div><div class="line"><a name="l00461"></a><span class="lineno"> 461</span>  _Stored_type _M_payload;</div><div class="line"><a name="l00462"></a><span class="lineno"> 462</span>  };</div><div class="line"><a name="l00463"></a><span class="lineno"> 463</span>  <span class="keywordtype">bool</span> _M_engaged = <span class="keyword">false</span>;</div><div class="line"><a name="l00464"></a><span class="lineno"> 464</span>  };</div><div class="line"><a name="l00465"></a><span class="lineno"> 465</span> </div><div class="line"><a name="l00466"></a><span class="lineno"> 466</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00467"></a><span class="lineno"> 467</span>  <span class="keyword">class </span><a class="code" href="a09988.html">optional</a>;</div><div class="line"><a name="l00468"></a><span class="lineno"> 468</span> </div><div class="line"><a name="l00469"></a><span class="lineno"> 469</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp, <span class="keyword">typename</span> _Up></div><div class="line"><a name="l00470"></a><span class="lineno"> 470</span>  <span class="keyword">using</span> __converts_from_optional =</div><div class="line"><a name="l00471"></a><span class="lineno"> 471</span>  __or_<is_constructible<_Tp, const optional<_Up>&>,</div><div class="line"><a name="l00472"></a><span class="lineno"> 472</span>  <a class="code" href="a03572.html">is_constructible<_Tp, optional<_Up></a>&>,</div><div class="line"><a name="l00473"></a><span class="lineno"> 473</span>  <a class="code" href="a03572.html">is_constructible<_Tp, const optional<_Up></a>&&>,</div><div class="line"><a name="l00474"></a><span class="lineno"> 474</span>  <a class="code" href="a03572.html">is_constructible<_Tp, optional<_Up></a>&&>,</div><div class="line"><a name="l00475"></a><span class="lineno"> 475</span>  <a class="code" href="a03900.html">is_convertible<const optional<_Up></a>&, _Tp>,</div><div class="line"><a name="l00476"></a><span class="lineno"> 476</span>  <a class="code" href="a03900.html">is_convertible<optional<_Up></a>&, _Tp>,</div><div class="line"><a name="l00477"></a><span class="lineno"> 477</span>  <a class="code" href="a03900.html">is_convertible<const optional<_Up></a>&&, _Tp>,</div><div class="line"><a name="l00478"></a><span class="lineno"> 478</span>  <a class="code" href="a03900.html">is_convertible<optional<_Up></a>&&, _Tp>>;</div><div class="line"><a name="l00479"></a><span class="lineno"> 479</span> </div><div class="line"><a name="l00480"></a><span class="lineno"> 480</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp, <span class="keyword">typename</span> _Up></div><div class="line"><a name="l00481"></a><span class="lineno"> 481</span>  <span class="keyword">using</span> __assigns_from_optional =</div><div class="line"><a name="l00482"></a><span class="lineno"> 482</span>  __or_<is_assignable<_Tp&, const optional<_Up>&>,</div><div class="line"><a name="l00483"></a><span class="lineno"> 483</span>  <a class="code" href="a03680.html">is_assignable<_Tp&, optional<_Up></a>&>,</div><div class="line"><a name="l00484"></a><span class="lineno"> 484</span>  <a class="code" href="a03680.html">is_assignable<_Tp&, const optional<_Up></a>&&>,</div><div class="line"><a name="l00485"></a><span class="lineno"> 485</span>  <a class="code" href="a03680.html">is_assignable<_Tp&, optional<_Up></a>&&>>;</div><div class="line"><a name="l00486"></a><span class="lineno"> 486</span> <span class="comment"></span></div><div class="line"><a name="l00487"></a><span class="lineno"> 487</span> <span class="comment"> /**</span></div><div class="line"><a name="l00488"></a><span class="lineno"> 488</span> <span class="comment"> * @brief Class template for optional values.</span></div><div class="line"><a name="l00489"></a><span class="lineno"> 489</span> <span class="comment"> */</span></div><div class="line"><a name="l00490"></a><span class="lineno"> 490</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00491"></a><span class="lineno"> 491</span>  <span class="keyword">class </span><a class="code" href="a09988.html">optional</a></div><div class="line"><a name="l00492"></a><span class="lineno"> 492</span>  : <span class="keyword">private</span> <a class="code" href="a10024.html">_Optional_base</a><_Tp>,</div><div class="line"><a name="l00493"></a><span class="lineno"> 493</span>  <span class="keyword">private</span> <a class="code" href="a05348.html">_Enable_copy_move</a><</div><div class="line"><a name="l00494"></a><span class="lineno"> 494</span>  <span class="comment">// Copy constructor.</span></div><div class="line"><a name="l00495"></a><span class="lineno"> 495</span>  is_copy_constructible<_Tp>::value,</div><div class="line"><a name="l00496"></a><span class="lineno"> 496</span>  <span class="comment">// Copy assignment.</span></div><div class="line"><a name="l00497"></a><span class="lineno"> 497</span>  __and_<is_copy_constructible<_Tp>, is_copy_assignable<_Tp>>::value,</div><div class="line"><a name="l00498"></a><span class="lineno"> 498</span>  <span class="comment">// Move constructor.</span></div><div class="line"><a name="l00499"></a><span class="lineno"> 499</span>  is_move_constructible<_Tp>::value,</div><div class="line"><a name="l00500"></a><span class="lineno"> 500</span>  <span class="comment">// Move assignment.</span></div><div class="line"><a name="l00501"></a><span class="lineno"> 501</span>  __and_<is_move_constructible<_Tp>, is_move_assignable<_Tp>>::value,</div><div class="line"><a name="l00502"></a><span class="lineno"> 502</span>  <span class="comment">// Unique tag type.</span></div><div class="line"><a name="l00503"></a><span class="lineno"> 503</span>  optional<_Tp>></div><div class="line"><a name="l00504"></a><span class="lineno"> 504</span>  {</div><div class="line"><a name="l00505"></a><span class="lineno"> 505</span>  static_assert(__and_<__not_<<a class="code" href="a03880.html">is_same</a><<a class="code" href="a01476.html#ga33d8994a84545d04adc29f8be0d12122">remove_cv_t<_Tp></a>, <a class="code" href="a09996.html">nullopt_t</a>>>,</div><div class="line"><a name="l00506"></a><span class="lineno"> 506</span>  __not_<<a class="code" href="a03880.html">is_same</a><<a class="code" href="a01476.html#ga33d8994a84545d04adc29f8be0d12122">remove_cv_t<_Tp></a>, <a class="code" href="a09992.html">in_place_t</a>>>,</div><div class="line"><a name="l00507"></a><span class="lineno"> 507</span>  __not_<<a class="code" href="a03396.html">is_reference<_Tp></a>>>(),</div><div class="line"><a name="l00508"></a><span class="lineno"> 508</span>  <span class="stringliteral">"Invalid instantiation of optional<T>"</span>);</div><div class="line"><a name="l00509"></a><span class="lineno"> 509</span> </div><div class="line"><a name="l00510"></a><span class="lineno"> 510</span>  <span class="keyword">private</span>:</div><div class="line"><a name="l00511"></a><span class="lineno"> 511</span>  <span class="keyword">using</span> _Base = <a class="code" href="a10024.html">_Optional_base<_Tp></a>;</div><div class="line"><a name="l00512"></a><span class="lineno"> 512</span> </div><div class="line"><a name="l00513"></a><span class="lineno"> 513</span>  <span class="keyword">public</span>:</div><div class="line"><a name="l00514"></a><span class="lineno"> 514</span>  <span class="keyword">using</span> value_type = _Tp;</div><div class="line"><a name="l00515"></a><span class="lineno"> 515</span> </div><div class="line"><a name="l00516"></a><span class="lineno"> 516</span>  <span class="comment">// _Optional_base has the responsibility for construction.</span></div><div class="line"><a name="l00517"></a><span class="lineno"> 517</span>  <span class="keyword">using</span> _Base::_Base;</div><div class="line"><a name="l00518"></a><span class="lineno"> 518</span> </div><div class="line"><a name="l00519"></a><span class="lineno"> 519</span>  constexpr <a class="code" href="a09988.html">optional</a>() = <span class="keywordflow">default</span>;</div><div class="line"><a name="l00520"></a><span class="lineno"> 520</span>  <span class="comment">// Converting constructors for engaged optionals.</span></div><div class="line"><a name="l00521"></a><span class="lineno"> 521</span>  <span class="keyword">template</span> <<span class="keyword">typename</span> _Up = _Tp,</div><div class="line"><a name="l00522"></a><span class="lineno"> 522</span>  <a class="code" href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">enable_if_t</a><__and_<</div><div class="line"><a name="l00523"></a><span class="lineno"> 523</span>  __not_<is_same<optional<_Tp>, <a class="code" href="a01476.html#gabe26c12710bb4c683badfaf0a586c5be">decay_t<_Up></a>>>,</div><div class="line"><a name="l00524"></a><span class="lineno"> 524</span>  <a class="code" href="a03572.html">is_constructible<_Tp, _Up&&></a>,</div><div class="line"><a name="l00525"></a><span class="lineno"> 525</span>  <a class="code" href="a03900.html">is_convertible<_Up&&, _Tp></a></div><div class="line"><a name="l00526"></a><span class="lineno"> 526</span>  >::value, <span class="keywordtype">bool</span>> = <span class="keyword">true</span>></div><div class="line"><a name="l00527"></a><span class="lineno"> 527</span>  constexpr <a class="code" href="a09988.html">optional</a>(_Up&& __t)</div><div class="line"><a name="l00528"></a><span class="lineno"> 528</span>  : _Base(<a class="code" href="a01515.html#ga69b3880c858acc1b7f88478d209b2fb3">in_place</a>, <a class="code" href="a01538.html">std</a>::<a class="code" href="a01477.html#gacb5baec338e12b99cb6bddea7506c7c6">forward</a><_Up>(__t)) { }</div><div class="line"><a name="l00529"></a><span class="lineno"> 529</span> </div><div class="line"><a name="l00530"></a><span class="lineno"> 530</span>  <span class="keyword">template</span> <<span class="keyword">typename</span> _Up = _Tp,</div><div class="line"><a name="l00531"></a><span class="lineno"> 531</span>  <a class="code" href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">enable_if_t</a><__and_<</div><div class="line"><a name="l00532"></a><span class="lineno"> 532</span>  __not_<is_same<optional<_Tp>, <a class="code" href="a01476.html#gabe26c12710bb4c683badfaf0a586c5be">decay_t<_Up></a>>>,</div><div class="line"><a name="l00533"></a><span class="lineno"> 533</span>  <a class="code" href="a03572.html">is_constructible<_Tp, _Up&&></a>,</div><div class="line"><a name="l00534"></a><span class="lineno"> 534</span>  __not_<is_convertible<_Up&&, _Tp>></div><div class="line"><a name="l00535"></a><span class="lineno"> 535</span>  >::value, <span class="keywordtype">bool</span>> = <span class="keyword">false</span>></div><div class="line"><a name="l00536"></a><span class="lineno"> 536</span>  <span class="keyword">explicit</span> constexpr optional(_Up&& __t)</div><div class="line"><a name="l00537"></a><span class="lineno"> 537</span>  : _Base(<a class="code" href="a01515.html#ga69b3880c858acc1b7f88478d209b2fb3">in_place</a>, <a class="code" href="a01538.html">std</a>::<a class="code" href="a01477.html#gacb5baec338e12b99cb6bddea7506c7c6">forward</a><_Up>(__t)) { }</div><div class="line"><a name="l00538"></a><span class="lineno"> 538</span> </div><div class="line"><a name="l00539"></a><span class="lineno"> 539</span>  <span class="keyword">template</span> <<span class="keyword">typename</span> _Up,</div><div class="line"><a name="l00540"></a><span class="lineno"> 540</span>  <a class="code" href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">enable_if_t</a><__and_<</div><div class="line"><a name="l00541"></a><span class="lineno"> 541</span>  __not_<is_same<_Tp, _Up>>,</div><div class="line"><a name="l00542"></a><span class="lineno"> 542</span>  <a class="code" href="a03572.html">is_constructible<_Tp, const _Up&></a>,</div><div class="line"><a name="l00543"></a><span class="lineno"> 543</span>  <a class="code" href="a03900.html">is_convertible<const _Up&, _Tp></a>,</div><div class="line"><a name="l00544"></a><span class="lineno"> 544</span>  __not_<__converts_from_optional<_Tp, _Up>></div><div class="line"><a name="l00545"></a><span class="lineno"> 545</span>  >::value, <span class="keywordtype">bool</span>> = <span class="keyword">true</span>></div><div class="line"><a name="l00546"></a><span class="lineno"> 546</span>  constexpr optional(<span class="keyword">const</span> optional<_Up>& __t)</div><div class="line"><a name="l00547"></a><span class="lineno"> 547</span>  {</div><div class="line"><a name="l00548"></a><span class="lineno"> 548</span>  <span class="keywordflow">if</span> (__t)</div><div class="line"><a name="l00549"></a><span class="lineno"> 549</span>  emplace(*__t);</div><div class="line"><a name="l00550"></a><span class="lineno"> 550</span>  }</div><div class="line"><a name="l00551"></a><span class="lineno"> 551</span> </div><div class="line"><a name="l00552"></a><span class="lineno"> 552</span>  <span class="keyword">template</span> <<span class="keyword">typename</span> _Up,</div><div class="line"><a name="l00553"></a><span class="lineno"> 553</span>  <a class="code" href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">enable_if_t</a><__and_<</div><div class="line"><a name="l00554"></a><span class="lineno"> 554</span>  __not_<is_same<_Tp, _Up>>,</div><div class="line"><a name="l00555"></a><span class="lineno"> 555</span>  is_constructible<_Tp, const _Up&>,</div><div class="line"><a name="l00556"></a><span class="lineno"> 556</span>  __not_<is_convertible<const _Up&, _Tp>>,</div><div class="line"><a name="l00557"></a><span class="lineno"> 557</span>  __not_<__converts_from_optional<_Tp, _Up>></div><div class="line"><a name="l00558"></a><span class="lineno"> 558</span>  >::value, <span class="keywordtype">bool</span>> = <span class="keyword">false</span>></div><div class="line"><a name="l00559"></a><span class="lineno"> 559</span>  <span class="keyword">explicit</span> constexpr optional(<span class="keyword">const</span> optional<_Up>& __t)</div><div class="line"><a name="l00560"></a><span class="lineno"> 560</span>  {</div><div class="line"><a name="l00561"></a><span class="lineno"> 561</span>  <span class="keywordflow">if</span> (__t)</div><div class="line"><a name="l00562"></a><span class="lineno"> 562</span>  emplace(*__t);</div><div class="line"><a name="l00563"></a><span class="lineno"> 563</span>  }</div><div class="line"><a name="l00564"></a><span class="lineno"> 564</span> </div><div class="line"><a name="l00565"></a><span class="lineno"> 565</span>  <span class="keyword">template</span> <<span class="keyword">typename</span> _Up,</div><div class="line"><a name="l00566"></a><span class="lineno"> 566</span>  <a class="code" href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">enable_if_t</a><__and_<</div><div class="line"><a name="l00567"></a><span class="lineno"> 567</span>  __not_<is_same<_Tp, _Up>>,</div><div class="line"><a name="l00568"></a><span class="lineno"> 568</span>  is_constructible<_Tp, _Up&&>,</div><div class="line"><a name="l00569"></a><span class="lineno"> 569</span>  is_convertible<_Up&&, _Tp>,</div><div class="line"><a name="l00570"></a><span class="lineno"> 570</span>  __not_<__converts_from_optional<_Tp, _Up>></div><div class="line"><a name="l00571"></a><span class="lineno"> 571</span>  >::value, <span class="keywordtype">bool</span>> = <span class="keyword">true</span>></div><div class="line"><a name="l00572"></a><span class="lineno"> 572</span>  constexpr optional(optional<_Up>&& __t)</div><div class="line"><a name="l00573"></a><span class="lineno"> 573</span>  {</div><div class="line"><a name="l00574"></a><span class="lineno"> 574</span>  <span class="keywordflow">if</span> (__t)</div><div class="line"><a name="l00575"></a><span class="lineno"> 575</span>  emplace(std::move(*__t));</div><div class="line"><a name="l00576"></a><span class="lineno"> 576</span>  }</div><div class="line"><a name="l00577"></a><span class="lineno"> 577</span> </div><div class="line"><a name="l00578"></a><span class="lineno"> 578</span>  <span class="keyword">template</span> <<span class="keyword">typename</span> _Up,</div><div class="line"><a name="l00579"></a><span class="lineno"> 579</span>  <a class="code" href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">enable_if_t</a><__and_<</div><div class="line"><a name="l00580"></a><span class="lineno"> 580</span>  __not_<is_same<_Tp, _Up>>,</div><div class="line"><a name="l00581"></a><span class="lineno"> 581</span>  is_constructible<_Tp, _Up&&>,</div><div class="line"><a name="l00582"></a><span class="lineno"> 582</span>  __not_<is_convertible<_Up&&, _Tp>>,</div><div class="line"><a name="l00583"></a><span class="lineno"> 583</span>  __not_<__converts_from_optional<_Tp, _Up>></div><div class="line"><a name="l00584"></a><span class="lineno"> 584</span>  >::value, <span class="keywordtype">bool</span>> = <span class="keyword">false</span>></div><div class="line"><a name="l00585"></a><span class="lineno"> 585</span>  <span class="keyword">explicit</span> constexpr optional(optional<_Up>&& __t)</div><div class="line"><a name="l00586"></a><span class="lineno"> 586</span>  {</div><div class="line"><a name="l00587"></a><span class="lineno"> 587</span>  <span class="keywordflow">if</span> (__t)</div><div class="line"><a name="l00588"></a><span class="lineno"> 588</span>  emplace(std::move(*__t));</div><div class="line"><a name="l00589"></a><span class="lineno"> 589</span>  }</div><div class="line"><a name="l00590"></a><span class="lineno"> 590</span> </div><div class="line"><a name="l00591"></a><span class="lineno"> 591</span>  <span class="comment">// [X.Y.4.3] (partly) Assignment.</span></div><div class="line"><a name="l00592"></a><span class="lineno"> 592</span>  optional&</div><div class="line"><a name="l00593"></a><span class="lineno"> 593</span>  operator=(nullopt_t) noexcept</div><div class="line"><a name="l00594"></a><span class="lineno"> 594</span>  {</div><div class="line"><a name="l00595"></a><span class="lineno"> 595</span>  this->_M_reset();</div><div class="line"><a name="l00596"></a><span class="lineno"> 596</span>  <span class="keywordflow">return</span> *<span class="keyword">this</span>;</div><div class="line"><a name="l00597"></a><span class="lineno"> 597</span>  }</div><div class="line"><a name="l00598"></a><span class="lineno"> 598</span> </div><div class="line"><a name="l00599"></a><span class="lineno"> 599</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Up = _Tp></div><div class="line"><a name="l00600"></a><span class="lineno"> 600</span>  <a class="code" href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">enable_if_t</a><__and_<</div><div class="line"><a name="l00601"></a><span class="lineno"> 601</span>  __not_<is_same<optional<_Tp>, decay_t<_Up>>>,</div><div class="line"><a name="l00602"></a><span class="lineno"> 602</span>  is_constructible<_Tp, _Up>,</div><div class="line"><a name="l00603"></a><span class="lineno"> 603</span>  __not_<__and_<is_scalar<_Tp>,</div><div class="line"><a name="l00604"></a><span class="lineno"> 604</span>  is_same<_Tp, decay_t<_Up>>>>,</div><div class="line"><a name="l00605"></a><span class="lineno"> 605</span>  is_assignable<_Tp&, _Up>>::value,</div><div class="line"><a name="l00606"></a><span class="lineno"> 606</span>  optional&></div><div class="line"><a name="l00607"></a><span class="lineno"> 607</span>  operator=(_Up&& __u)</div><div class="line"><a name="l00608"></a><span class="lineno"> 608</span>  {</div><div class="line"><a name="l00609"></a><span class="lineno"> 609</span>  <span class="keywordflow">if</span> (this->_M_is_engaged())</div><div class="line"><a name="l00610"></a><span class="lineno"> 610</span>  this->_M_get() = std::forward<_Up>(__u);</div><div class="line"><a name="l00611"></a><span class="lineno"> 611</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00612"></a><span class="lineno"> 612</span>  this->_M_construct(std::forward<_Up>(__u));</div><div class="line"><a name="l00613"></a><span class="lineno"> 613</span> </div><div class="line"><a name="l00614"></a><span class="lineno"> 614</span>  <span class="keywordflow">return</span> *<span class="keyword">this</span>;</div><div class="line"><a name="l00615"></a><span class="lineno"> 615</span>  }</div><div class="line"><a name="l00616"></a><span class="lineno"> 616</span> </div><div class="line"><a name="l00617"></a><span class="lineno"> 617</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Up></div><div class="line"><a name="l00618"></a><span class="lineno"> 618</span>  <a class="code" href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">enable_if_t</a><__and_<</div><div class="line"><a name="l00619"></a><span class="lineno"> 619</span>  __not_<is_same<_Tp, _Up>>,</div><div class="line"><a name="l00620"></a><span class="lineno"> 620</span>  is_constructible<_Tp, const _Up&>,</div><div class="line"><a name="l00621"></a><span class="lineno"> 621</span>  is_assignable<_Tp&, _Up>,</div><div class="line"><a name="l00622"></a><span class="lineno"> 622</span>  __not_<__converts_from_optional<_Tp, _Up>>,</div><div class="line"><a name="l00623"></a><span class="lineno"> 623</span>  __not_<__assigns_from_optional<_Tp, _Up>></div><div class="line"><a name="l00624"></a><span class="lineno"> 624</span>  >::value,</div><div class="line"><a name="l00625"></a><span class="lineno"> 625</span>  optional&></div><div class="line"><a name="l00626"></a><span class="lineno"> 626</span>  operator=(<span class="keyword">const</span> optional<_Up>& __u)</div><div class="line"><a name="l00627"></a><span class="lineno"> 627</span>  {</div><div class="line"><a name="l00628"></a><span class="lineno"> 628</span>  <span class="keywordflow">if</span> (__u)</div><div class="line"><a name="l00629"></a><span class="lineno"> 629</span>  {</div><div class="line"><a name="l00630"></a><span class="lineno"> 630</span>  <span class="keywordflow">if</span> (this->_M_is_engaged())</div><div class="line"><a name="l00631"></a><span class="lineno"> 631</span>  this->_M_get() = *__u;</div><div class="line"><a name="l00632"></a><span class="lineno"> 632</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00633"></a><span class="lineno"> 633</span>  this->_M_construct(*__u);</div><div class="line"><a name="l00634"></a><span class="lineno"> 634</span>  }</div><div class="line"><a name="l00635"></a><span class="lineno"> 635</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00636"></a><span class="lineno"> 636</span>  {</div><div class="line"><a name="l00637"></a><span class="lineno"> 637</span>  this->_M_reset();</div><div class="line"><a name="l00638"></a><span class="lineno"> 638</span>  }</div><div class="line"><a name="l00639"></a><span class="lineno"> 639</span>  <span class="keywordflow">return</span> *<span class="keyword">this</span>;</div><div class="line"><a name="l00640"></a><span class="lineno"> 640</span>  }</div><div class="line"><a name="l00641"></a><span class="lineno"> 641</span> </div><div class="line"><a name="l00642"></a><span class="lineno"> 642</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Up></div><div class="line"><a name="l00643"></a><span class="lineno"> 643</span>  <a class="code" href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">enable_if_t</a><__and_<</div><div class="line"><a name="l00644"></a><span class="lineno"> 644</span>  __not_<is_same<_Tp, _Up>>,</div><div class="line"><a name="l00645"></a><span class="lineno"> 645</span>  is_constructible<_Tp, _Up>,</div><div class="line"><a name="l00646"></a><span class="lineno"> 646</span>  is_assignable<_Tp&, _Up>,</div><div class="line"><a name="l00647"></a><span class="lineno"> 647</span>  __not_<__converts_from_optional<_Tp, _Up>>,</div><div class="line"><a name="l00648"></a><span class="lineno"> 648</span>  __not_<__assigns_from_optional<_Tp, _Up>></div><div class="line"><a name="l00649"></a><span class="lineno"> 649</span>  >::value,</div><div class="line"><a name="l00650"></a><span class="lineno"> 650</span>  optional&></div><div class="line"><a name="l00651"></a><span class="lineno"> 651</span>  operator=(optional<_Up>&& __u)</div><div class="line"><a name="l00652"></a><span class="lineno"> 652</span>  {</div><div class="line"><a name="l00653"></a><span class="lineno"> 653</span>  <span class="keywordflow">if</span> (__u)</div><div class="line"><a name="l00654"></a><span class="lineno"> 654</span>  {</div><div class="line"><a name="l00655"></a><span class="lineno"> 655</span>  <span class="keywordflow">if</span> (this->_M_is_engaged())</div><div class="line"><a name="l00656"></a><span class="lineno"> 656</span>  this->_M_get() = std::move(*__u);</div><div class="line"><a name="l00657"></a><span class="lineno"> 657</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00658"></a><span class="lineno"> 658</span>  this->_M_construct(std::move(*__u));</div><div class="line"><a name="l00659"></a><span class="lineno"> 659</span>  }</div><div class="line"><a name="l00660"></a><span class="lineno"> 660</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00661"></a><span class="lineno"> 661</span>  {</div><div class="line"><a name="l00662"></a><span class="lineno"> 662</span>  this->_M_reset();</div><div class="line"><a name="l00663"></a><span class="lineno"> 663</span>  }</div><div class="line"><a name="l00664"></a><span class="lineno"> 664</span> </div><div class="line"><a name="l00665"></a><span class="lineno"> 665</span>  <span class="keywordflow">return</span> *<span class="keyword">this</span>;</div><div class="line"><a name="l00666"></a><span class="lineno"> 666</span>  }</div><div class="line"><a name="l00667"></a><span class="lineno"> 667</span> </div><div class="line"><a name="l00668"></a><span class="lineno"> 668</span>  <span class="keyword">template</span><<span class="keyword">typename</span>... _Args></div><div class="line"><a name="l00669"></a><span class="lineno"> 669</span>  <a class="code" href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">enable_if_t</a><is_constructible<_Tp, _Args&&...>::value></div><div class="line"><a name="l00670"></a><span class="lineno"> 670</span>  emplace(_Args&&... __args)</div><div class="line"><a name="l00671"></a><span class="lineno"> 671</span>  {</div><div class="line"><a name="l00672"></a><span class="lineno"> 672</span>  this->_M_reset();</div><div class="line"><a name="l00673"></a><span class="lineno"> 673</span>  this->_M_construct(std::forward<_Args>(__args)...);</div><div class="line"><a name="l00674"></a><span class="lineno"> 674</span>  }</div><div class="line"><a name="l00675"></a><span class="lineno"> 675</span> </div><div class="line"><a name="l00676"></a><span class="lineno"> 676</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Up, <span class="keyword">typename</span>... _Args></div><div class="line"><a name="l00677"></a><span class="lineno"> 677</span>  enable_if_t<is_constructible<_Tp, initializer_list<_Up>&,</div><div class="line"><a name="l00678"></a><span class="lineno"> 678</span>  _Args&&...>::value></div><div class="line"><a name="l00679"></a><span class="lineno"> 679</span>  emplace(initializer_list<_Up> __il, _Args&&... __args)</div><div class="line"><a name="l00680"></a><span class="lineno"> 680</span>  {</div><div class="line"><a name="l00681"></a><span class="lineno"> 681</span>  this->_M_reset();</div><div class="line"><a name="l00682"></a><span class="lineno"> 682</span>  this->_M_construct(__il, std::forward<_Args>(__args)...);</div><div class="line"><a name="l00683"></a><span class="lineno"> 683</span>  }</div><div class="line"><a name="l00684"></a><span class="lineno"> 684</span> </div><div class="line"><a name="l00685"></a><span class="lineno"> 685</span>  <span class="comment">// [X.Y.4.2] Destructor is implicit, implemented in _Optional_base.</span></div><div class="line"><a name="l00686"></a><span class="lineno"> 686</span> </div><div class="line"><a name="l00687"></a><span class="lineno"> 687</span>  <span class="comment">// [X.Y.4.4] Swap.</span></div><div class="line"><a name="l00688"></a><span class="lineno"> 688</span>  <span class="keywordtype">void</span></div><div class="line"><a name="l00689"></a><span class="lineno"> 689</span>  swap(optional& __other)</div><div class="line"><a name="l00690"></a><span class="lineno"> 690</span>  noexcept(is_nothrow_move_constructible<_Tp>()</div><div class="line"><a name="l00691"></a><span class="lineno"> 691</span>  && __is_nothrow_swappable<_Tp>::value)</div><div class="line"><a name="l00692"></a><span class="lineno"> 692</span>  {</div><div class="line"><a name="l00693"></a><span class="lineno"> 693</span>  <span class="keyword">using</span> std::swap;</div><div class="line"><a name="l00694"></a><span class="lineno"> 694</span> </div><div class="line"><a name="l00695"></a><span class="lineno"> 695</span>  <span class="keywordflow">if</span> (this->_M_is_engaged() && __other._M_is_engaged())</div><div class="line"><a name="l00696"></a><span class="lineno"> 696</span>  swap(this->_M_get(), __other._M_get());</div><div class="line"><a name="l00697"></a><span class="lineno"> 697</span>  <span class="keywordflow">else</span> <span class="keywordflow">if</span> (this->_M_is_engaged())</div><div class="line"><a name="l00698"></a><span class="lineno"> 698</span>  {</div><div class="line"><a name="l00699"></a><span class="lineno"> 699</span>  __other._M_construct(std::move(this->_M_get()));</div><div class="line"><a name="l00700"></a><span class="lineno"> 700</span>  this->_M_destruct();</div><div class="line"><a name="l00701"></a><span class="lineno"> 701</span>  }</div><div class="line"><a name="l00702"></a><span class="lineno"> 702</span>  <span class="keywordflow">else</span> <span class="keywordflow">if</span> (__other._M_is_engaged())</div><div class="line"><a name="l00703"></a><span class="lineno"> 703</span>  {</div><div class="line"><a name="l00704"></a><span class="lineno"> 704</span>  this->_M_construct(std::move(__other._M_get()));</div><div class="line"><a name="l00705"></a><span class="lineno"> 705</span>  __other._M_destruct();</div><div class="line"><a name="l00706"></a><span class="lineno"> 706</span>  }</div><div class="line"><a name="l00707"></a><span class="lineno"> 707</span>  }</div><div class="line"><a name="l00708"></a><span class="lineno"> 708</span> </div><div class="line"><a name="l00709"></a><span class="lineno"> 709</span>  <span class="comment">// [X.Y.4.5] Observers.</span></div><div class="line"><a name="l00710"></a><span class="lineno"> 710</span>  constexpr <span class="keyword">const</span> _Tp*</div><div class="line"><a name="l00711"></a><span class="lineno"> 711</span>  operator->()<span class="keyword"> const</span></div><div class="line"><a name="l00712"></a><span class="lineno"> 712</span> <span class="keyword"> </span>{</div><div class="line"><a name="l00713"></a><span class="lineno"> 713</span> <span class="preprocessor">#ifndef __cpp_lib_addressof_constexpr</span></div><div class="line"><a name="l00714"></a><span class="lineno"> 714</span>  <span class="keywordflow">return</span> <a class="code" href="a01515.html#gaec6098e9e49d3b1918c5de29086aeead">__constexpr_addressof</a>(this->_M_get());</div><div class="line"><a name="l00715"></a><span class="lineno"> 715</span> <span class="preprocessor">#else</span></div><div class="line"><a name="l00716"></a><span class="lineno"> 716</span>  <span class="keywordflow">return</span> <a class="code" href="a01477.html#ga1954d5552e24586051011312041033f6">std::__addressof</a>(this->_M_get());</div><div class="line"><a name="l00717"></a><span class="lineno"> 717</span> <span class="preprocessor">#endif</span></div><div class="line"><a name="l00718"></a><span class="lineno"> 718</span>  }</div><div class="line"><a name="l00719"></a><span class="lineno"> 719</span> </div><div class="line"><a name="l00720"></a><span class="lineno"> 720</span>  _Tp*</div><div class="line"><a name="l00721"></a><span class="lineno"> 721</span>  operator->()</div><div class="line"><a name="l00722"></a><span class="lineno"> 722</span>  { <span class="keywordflow">return</span> <a class="code" href="a01477.html#ga1954d5552e24586051011312041033f6">std::__addressof</a>(this->_M_get()); }</div><div class="line"><a name="l00723"></a><span class="lineno"> 723</span> </div><div class="line"><a name="l00724"></a><span class="lineno"> 724</span>  constexpr <span class="keyword">const</span> _Tp&</div><div class="line"><a name="l00725"></a><span class="lineno"> 725</span>  operator*() const&</div><div class="line"><a name="l00726"></a><span class="lineno"> 726</span>  { <span class="keywordflow">return</span> this->_M_get(); }</div><div class="line"><a name="l00727"></a><span class="lineno"> 727</span> </div><div class="line"><a name="l00728"></a><span class="lineno"> 728</span>  constexpr _Tp&</div><div class="line"><a name="l00729"></a><span class="lineno"> 729</span>  operator*()&</div><div class="line"><a name="l00730"></a><span class="lineno"> 730</span>  { <span class="keywordflow">return</span> this->_M_get(); }</div><div class="line"><a name="l00731"></a><span class="lineno"> 731</span> </div><div class="line"><a name="l00732"></a><span class="lineno"> 732</span>  constexpr _Tp&&</div><div class="line"><a name="l00733"></a><span class="lineno"> 733</span>  operator*()&&</div><div class="line"><a name="l00734"></a><span class="lineno"> 734</span>  { <span class="keywordflow">return</span> std::move(this->_M_get()); }</div><div class="line"><a name="l00735"></a><span class="lineno"> 735</span> </div><div class="line"><a name="l00736"></a><span class="lineno"> 736</span>  constexpr <span class="keyword">const</span> _Tp&&</div><div class="line"><a name="l00737"></a><span class="lineno"> 737</span>  operator*() const&&</div><div class="line"><a name="l00738"></a><span class="lineno"> 738</span>  { <span class="keywordflow">return</span> std::move(this->_M_get()); }</div><div class="line"><a name="l00739"></a><span class="lineno"> 739</span> </div><div class="line"><a name="l00740"></a><span class="lineno"> 740</span>  constexpr <span class="keyword">explicit</span> <span class="keyword">operator</span> bool() const noexcept</div><div class="line"><a name="l00741"></a><span class="lineno"> 741</span>  { <span class="keywordflow">return</span> this->_M_is_engaged(); }</div><div class="line"><a name="l00742"></a><span class="lineno"> 742</span> </div><div class="line"><a name="l00743"></a><span class="lineno"> 743</span>  constexpr <span class="keyword">const</span> _Tp&</div><div class="line"><a name="l00744"></a><span class="lineno"> 744</span>  value() const&</div><div class="line"><a name="l00745"></a><span class="lineno"> 745</span>  {</div><div class="line"><a name="l00746"></a><span class="lineno"> 746</span>  <span class="keywordflow">return</span> this->_M_is_engaged()</div><div class="line"><a name="l00747"></a><span class="lineno"> 747</span>  ? this->_M_get()</div><div class="line"><a name="l00748"></a><span class="lineno"> 748</span>  : (__throw_bad_optional_access(<span class="stringliteral">"Attempt to access value of a "</span></div><div class="line"><a name="l00749"></a><span class="lineno"> 749</span>  <span class="stringliteral">"disengaged optional object"</span>),</div><div class="line"><a name="l00750"></a><span class="lineno"> 750</span>  this->_M_get());</div><div class="line"><a name="l00751"></a><span class="lineno"> 751</span>  }</div><div class="line"><a name="l00752"></a><span class="lineno"> 752</span> </div><div class="line"><a name="l00753"></a><span class="lineno"> 753</span>  constexpr _Tp&</div><div class="line"><a name="l00754"></a><span class="lineno"> 754</span>  value()&</div><div class="line"><a name="l00755"></a><span class="lineno"> 755</span>  {</div><div class="line"><a name="l00756"></a><span class="lineno"> 756</span>  <span class="keywordflow">return</span> this->_M_is_engaged()</div><div class="line"><a name="l00757"></a><span class="lineno"> 757</span>  ? this->_M_get()</div><div class="line"><a name="l00758"></a><span class="lineno"> 758</span>  : (__throw_bad_optional_access(<span class="stringliteral">"Attempt to access value of a "</span></div><div class="line"><a name="l00759"></a><span class="lineno"> 759</span>  <span class="stringliteral">"disengaged optional object"</span>),</div><div class="line"><a name="l00760"></a><span class="lineno"> 760</span>  this->_M_get());</div><div class="line"><a name="l00761"></a><span class="lineno"> 761</span>  }</div><div class="line"><a name="l00762"></a><span class="lineno"> 762</span> </div><div class="line"><a name="l00763"></a><span class="lineno"> 763</span>  constexpr _Tp&&</div><div class="line"><a name="l00764"></a><span class="lineno"> 764</span>  value()&&</div><div class="line"><a name="l00765"></a><span class="lineno"> 765</span>  {</div><div class="line"><a name="l00766"></a><span class="lineno"> 766</span>  <span class="keywordflow">return</span> this->_M_is_engaged()</div><div class="line"><a name="l00767"></a><span class="lineno"> 767</span>  ? std::move(this->_M_get())</div><div class="line"><a name="l00768"></a><span class="lineno"> 768</span>  : (__throw_bad_optional_access(<span class="stringliteral">"Attempt to access value of a "</span></div><div class="line"><a name="l00769"></a><span class="lineno"> 769</span>  <span class="stringliteral">"disengaged optional object"</span>),</div><div class="line"><a name="l00770"></a><span class="lineno"> 770</span>  <a class="code" href="a01538.html">std</a>::move(this->_M_get()));</div><div class="line"><a name="l00771"></a><span class="lineno"> 771</span>  }</div><div class="line"><a name="l00772"></a><span class="lineno"> 772</span> </div><div class="line"><a name="l00773"></a><span class="lineno"> 773</span>  constexpr <span class="keyword">const</span> _Tp&&</div><div class="line"><a name="l00774"></a><span class="lineno"> 774</span>  value() const&&</div><div class="line"><a name="l00775"></a><span class="lineno"> 775</span>  {</div><div class="line"><a name="l00776"></a><span class="lineno"> 776</span>  <span class="keywordflow">return</span> this->_M_is_engaged()</div><div class="line"><a name="l00777"></a><span class="lineno"> 777</span>  ? std::move(this->_M_get())</div><div class="line"><a name="l00778"></a><span class="lineno"> 778</span>  : (__throw_bad_optional_access(<span class="stringliteral">"Attempt to access value of a "</span></div><div class="line"><a name="l00779"></a><span class="lineno"> 779</span>  <span class="stringliteral">"disengaged optional object"</span>),</div><div class="line"><a name="l00780"></a><span class="lineno"> 780</span>  <a class="code" href="a01538.html">std</a>::move(this->_M_get()));</div><div class="line"><a name="l00781"></a><span class="lineno"> 781</span>  }</div><div class="line"><a name="l00782"></a><span class="lineno"> 782</span> </div><div class="line"><a name="l00783"></a><span class="lineno"> 783</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Up></div><div class="line"><a name="l00784"></a><span class="lineno"> 784</span>  constexpr _Tp</div><div class="line"><a name="l00785"></a><span class="lineno"> 785</span>  value_or(_Up&& __u) <span class="keyword">const</span>&</div><div class="line"><a name="l00786"></a><span class="lineno"> 786</span>  {</div><div class="line"><a name="l00787"></a><span class="lineno"> 787</span>  static_assert(__and_<is_copy_constructible<_Tp>,</div><div class="line"><a name="l00788"></a><span class="lineno"> 788</span>  is_convertible<_Up&&, _Tp>>(),</div><div class="line"><a name="l00789"></a><span class="lineno"> 789</span>  <span class="stringliteral">"Cannot return value"</span>);</div><div class="line"><a name="l00790"></a><span class="lineno"> 790</span> </div><div class="line"><a name="l00791"></a><span class="lineno"> 791</span>  <span class="keywordflow">return</span> this->_M_is_engaged()</div><div class="line"><a name="l00792"></a><span class="lineno"> 792</span>  ? this->_M_get()</div><div class="line"><a name="l00793"></a><span class="lineno"> 793</span>  : static_cast<_Tp>(<a class="code" href="a01538.html">std</a>::<a class="code" href="a01477.html#gacb5baec338e12b99cb6bddea7506c7c6">forward</a><_Up>(__u));</div><div class="line"><a name="l00794"></a><span class="lineno"> 794</span>  }</div><div class="line"><a name="l00795"></a><span class="lineno"> 795</span> </div><div class="line"><a name="l00796"></a><span class="lineno"> 796</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Up></div><div class="line"><a name="l00797"></a><span class="lineno"> 797</span>  _Tp</div><div class="line"><a name="l00798"></a><span class="lineno"> 798</span>  value_or(_Up&& __u) &&</div><div class="line"><a name="l00799"></a><span class="lineno"> 799</span>  {</div><div class="line"><a name="l00800"></a><span class="lineno"> 800</span>  static_assert(__and_<is_move_constructible<_Tp>,</div><div class="line"><a name="l00801"></a><span class="lineno"> 801</span>  is_convertible<_Up&&, _Tp>>(),</div><div class="line"><a name="l00802"></a><span class="lineno"> 802</span>  <span class="stringliteral">"Cannot return value"</span> );</div><div class="line"><a name="l00803"></a><span class="lineno"> 803</span> </div><div class="line"><a name="l00804"></a><span class="lineno"> 804</span>  <span class="keywordflow">return</span> this->_M_is_engaged()</div><div class="line"><a name="l00805"></a><span class="lineno"> 805</span>  ? std::move(this->_M_get())</div><div class="line"><a name="l00806"></a><span class="lineno"> 806</span>  : static_cast<_Tp>(<a class="code" href="a01538.html">std</a>::<a class="code" href="a01477.html#gacb5baec338e12b99cb6bddea7506c7c6">forward</a><_Up>(__u));</div><div class="line"><a name="l00807"></a><span class="lineno"> 807</span>  }</div><div class="line"><a name="l00808"></a><span class="lineno"> 808</span>  };</div><div class="line"><a name="l00809"></a><span class="lineno"> 809</span> </div><div class="line"><a name="l00810"></a><span class="lineno"> 810</span>  <span class="comment">// [X.Y.8] Comparisons between optional values.</span></div><div class="line"><a name="l00811"></a><span class="lineno"> 811</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00812"></a><span class="lineno"> 812</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00813"></a><span class="lineno"> 813</span>  operator==(<span class="keyword">const</span> optional<_Tp>& __lhs, <span class="keyword">const</span> optional<_Tp>& __rhs)</div><div class="line"><a name="l00814"></a><span class="lineno"> 814</span>  {</div><div class="line"><a name="l00815"></a><span class="lineno"> 815</span>  <span class="keywordflow">return</span> static_cast<bool>(__lhs) == static_cast<bool>(__rhs)</div><div class="line"><a name="l00816"></a><span class="lineno"> 816</span>  && (!__lhs || *__lhs == *__rhs);</div><div class="line"><a name="l00817"></a><span class="lineno"> 817</span>  }</div><div class="line"><a name="l00818"></a><span class="lineno"> 818</span> </div><div class="line"><a name="l00819"></a><span class="lineno"> 819</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00820"></a><span class="lineno"> 820</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00821"></a><span class="lineno"> 821</span>  operator!=(<span class="keyword">const</span> optional<_Tp>& __lhs, <span class="keyword">const</span> optional<_Tp>& __rhs)</div><div class="line"><a name="l00822"></a><span class="lineno"> 822</span>  { <span class="keywordflow">return</span> !(__lhs == __rhs); }</div><div class="line"><a name="l00823"></a><span class="lineno"> 823</span> </div><div class="line"><a name="l00824"></a><span class="lineno"> 824</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00825"></a><span class="lineno"> 825</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00826"></a><span class="lineno"> 826</span>  operator<(<span class="keyword">const</span> optional<_Tp>& __lhs, <span class="keyword">const</span> optional<_Tp>& __rhs)</div><div class="line"><a name="l00827"></a><span class="lineno"> 827</span>  {</div><div class="line"><a name="l00828"></a><span class="lineno"> 828</span>  <span class="keywordflow">return</span> static_cast<bool>(__rhs) && (!__lhs || *__lhs < *__rhs);</div><div class="line"><a name="l00829"></a><span class="lineno"> 829</span>  }</div><div class="line"><a name="l00830"></a><span class="lineno"> 830</span> </div><div class="line"><a name="l00831"></a><span class="lineno"> 831</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00832"></a><span class="lineno"> 832</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00833"></a><span class="lineno"> 833</span>  operator>(<span class="keyword">const</span> optional<_Tp>& __lhs, <span class="keyword">const</span> optional<_Tp>& __rhs)</div><div class="line"><a name="l00834"></a><span class="lineno"> 834</span>  { <span class="keywordflow">return</span> __rhs < __lhs; }</div><div class="line"><a name="l00835"></a><span class="lineno"> 835</span> </div><div class="line"><a name="l00836"></a><span class="lineno"> 836</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00837"></a><span class="lineno"> 837</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00838"></a><span class="lineno"> 838</span>  operator<=(<span class="keyword">const</span> optional<_Tp>& __lhs, <span class="keyword">const</span> optional<_Tp>& __rhs)</div><div class="line"><a name="l00839"></a><span class="lineno"> 839</span>  { <span class="keywordflow">return</span> !(__rhs < __lhs); }</div><div class="line"><a name="l00840"></a><span class="lineno"> 840</span> </div><div class="line"><a name="l00841"></a><span class="lineno"> 841</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00842"></a><span class="lineno"> 842</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00843"></a><span class="lineno"> 843</span>  operator>=(<span class="keyword">const</span> optional<_Tp>& __lhs, <span class="keyword">const</span> optional<_Tp>& __rhs)</div><div class="line"><a name="l00844"></a><span class="lineno"> 844</span>  { <span class="keywordflow">return</span> !(__lhs < __rhs); }</div><div class="line"><a name="l00845"></a><span class="lineno"> 845</span> </div><div class="line"><a name="l00846"></a><span class="lineno"> 846</span>  <span class="comment">// [X.Y.9] Comparisons with nullopt.</span></div><div class="line"><a name="l00847"></a><span class="lineno"> 847</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00848"></a><span class="lineno"> 848</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00849"></a><span class="lineno"> 849</span>  operator==(<span class="keyword">const</span> optional<_Tp>& __lhs, nullopt_t) noexcept</div><div class="line"><a name="l00850"></a><span class="lineno"> 850</span>  { <span class="keywordflow">return</span> !__lhs; }</div><div class="line"><a name="l00851"></a><span class="lineno"> 851</span> </div><div class="line"><a name="l00852"></a><span class="lineno"> 852</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00853"></a><span class="lineno"> 853</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00854"></a><span class="lineno"> 854</span>  operator==(nullopt_t, <span class="keyword">const</span> optional<_Tp>& __rhs) noexcept</div><div class="line"><a name="l00855"></a><span class="lineno"> 855</span>  { <span class="keywordflow">return</span> !__rhs; }</div><div class="line"><a name="l00856"></a><span class="lineno"> 856</span> </div><div class="line"><a name="l00857"></a><span class="lineno"> 857</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00858"></a><span class="lineno"> 858</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00859"></a><span class="lineno"> 859</span>  operator!=(<span class="keyword">const</span> optional<_Tp>& __lhs, nullopt_t) noexcept</div><div class="line"><a name="l00860"></a><span class="lineno"> 860</span>  { <span class="keywordflow">return</span> static_cast<bool>(__lhs); }</div><div class="line"><a name="l00861"></a><span class="lineno"> 861</span> </div><div class="line"><a name="l00862"></a><span class="lineno"> 862</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00863"></a><span class="lineno"> 863</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00864"></a><span class="lineno"> 864</span>  operator!=(nullopt_t, <span class="keyword">const</span> optional<_Tp>& __rhs) noexcept</div><div class="line"><a name="l00865"></a><span class="lineno"> 865</span>  { <span class="keywordflow">return</span> static_cast<bool>(__rhs); }</div><div class="line"><a name="l00866"></a><span class="lineno"> 866</span> </div><div class="line"><a name="l00867"></a><span class="lineno"> 867</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00868"></a><span class="lineno"> 868</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00869"></a><span class="lineno"> 869</span>  operator<(<span class="keyword">const</span> optional<_Tp>& <span class="comment">/* __lhs */</span>, nullopt_t) noexcept</div><div class="line"><a name="l00870"></a><span class="lineno"> 870</span>  { <span class="keywordflow">return</span> <span class="keyword">false</span>; }</div><div class="line"><a name="l00871"></a><span class="lineno"> 871</span> </div><div class="line"><a name="l00872"></a><span class="lineno"> 872</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00873"></a><span class="lineno"> 873</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00874"></a><span class="lineno"> 874</span>  operator<(nullopt_t, <span class="keyword">const</span> optional<_Tp>& __rhs) noexcept</div><div class="line"><a name="l00875"></a><span class="lineno"> 875</span>  { <span class="keywordflow">return</span> static_cast<bool>(__rhs); }</div><div class="line"><a name="l00876"></a><span class="lineno"> 876</span> </div><div class="line"><a name="l00877"></a><span class="lineno"> 877</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00878"></a><span class="lineno"> 878</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00879"></a><span class="lineno"> 879</span>  operator>(<span class="keyword">const</span> optional<_Tp>& __lhs, nullopt_t) noexcept</div><div class="line"><a name="l00880"></a><span class="lineno"> 880</span>  { <span class="keywordflow">return</span> static_cast<bool>(__lhs); }</div><div class="line"><a name="l00881"></a><span class="lineno"> 881</span> </div><div class="line"><a name="l00882"></a><span class="lineno"> 882</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00883"></a><span class="lineno"> 883</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00884"></a><span class="lineno"> 884</span>  operator>(nullopt_t, <span class="keyword">const</span> optional<_Tp>& <span class="comment">/* __rhs */</span>) noexcept</div><div class="line"><a name="l00885"></a><span class="lineno"> 885</span>  { <span class="keywordflow">return</span> <span class="keyword">false</span>; }</div><div class="line"><a name="l00886"></a><span class="lineno"> 886</span> </div><div class="line"><a name="l00887"></a><span class="lineno"> 887</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00888"></a><span class="lineno"> 888</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00889"></a><span class="lineno"> 889</span>  operator<=(<span class="keyword">const</span> optional<_Tp>& __lhs, nullopt_t) noexcept</div><div class="line"><a name="l00890"></a><span class="lineno"> 890</span>  { <span class="keywordflow">return</span> !__lhs; }</div><div class="line"><a name="l00891"></a><span class="lineno"> 891</span> </div><div class="line"><a name="l00892"></a><span class="lineno"> 892</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00893"></a><span class="lineno"> 893</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00894"></a><span class="lineno"> 894</span>  operator<=(nullopt_t, <span class="keyword">const</span> optional<_Tp>& <span class="comment">/* __rhs */</span>) noexcept</div><div class="line"><a name="l00895"></a><span class="lineno"> 895</span>  { <span class="keywordflow">return</span> <span class="keyword">true</span>; }</div><div class="line"><a name="l00896"></a><span class="lineno"> 896</span> </div><div class="line"><a name="l00897"></a><span class="lineno"> 897</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00898"></a><span class="lineno"> 898</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00899"></a><span class="lineno"> 899</span>  operator>=(<span class="keyword">const</span> optional<_Tp>& <span class="comment">/* __lhs */</span>, nullopt_t) noexcept</div><div class="line"><a name="l00900"></a><span class="lineno"> 900</span>  { <span class="keywordflow">return</span> <span class="keyword">true</span>; }</div><div class="line"><a name="l00901"></a><span class="lineno"> 901</span> </div><div class="line"><a name="l00902"></a><span class="lineno"> 902</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00903"></a><span class="lineno"> 903</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00904"></a><span class="lineno"> 904</span>  operator>=(nullopt_t, <span class="keyword">const</span> optional<_Tp>& __rhs) noexcept</div><div class="line"><a name="l00905"></a><span class="lineno"> 905</span>  { <span class="keywordflow">return</span> !__rhs; }</div><div class="line"><a name="l00906"></a><span class="lineno"> 906</span> </div><div class="line"><a name="l00907"></a><span class="lineno"> 907</span>  <span class="comment">// [X.Y.10] Comparisons with value type.</span></div><div class="line"><a name="l00908"></a><span class="lineno"> 908</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00909"></a><span class="lineno"> 909</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00910"></a><span class="lineno"> 910</span>  operator==(<span class="keyword">const</span> optional<_Tp>& __lhs, <span class="keyword">const</span> _Tp& __rhs)</div><div class="line"><a name="l00911"></a><span class="lineno"> 911</span>  { <span class="keywordflow">return</span> __lhs && *__lhs == __rhs; }</div><div class="line"><a name="l00912"></a><span class="lineno"> 912</span> </div><div class="line"><a name="l00913"></a><span class="lineno"> 913</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00914"></a><span class="lineno"> 914</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00915"></a><span class="lineno"> 915</span>  operator==(<span class="keyword">const</span> _Tp& __lhs, <span class="keyword">const</span> optional<_Tp>& __rhs)</div><div class="line"><a name="l00916"></a><span class="lineno"> 916</span>  { <span class="keywordflow">return</span> __rhs && __lhs == *__rhs; }</div><div class="line"><a name="l00917"></a><span class="lineno"> 917</span> </div><div class="line"><a name="l00918"></a><span class="lineno"> 918</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00919"></a><span class="lineno"> 919</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00920"></a><span class="lineno"> 920</span>  operator!=(<span class="keyword">const</span> optional<_Tp>& __lhs, _Tp <span class="keyword">const</span>& __rhs)</div><div class="line"><a name="l00921"></a><span class="lineno"> 921</span>  { <span class="keywordflow">return</span> !__lhs || !(*__lhs == __rhs); }</div><div class="line"><a name="l00922"></a><span class="lineno"> 922</span> </div><div class="line"><a name="l00923"></a><span class="lineno"> 923</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00924"></a><span class="lineno"> 924</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00925"></a><span class="lineno"> 925</span>  operator!=(<span class="keyword">const</span> _Tp& __lhs, <span class="keyword">const</span> optional<_Tp>& __rhs)</div><div class="line"><a name="l00926"></a><span class="lineno"> 926</span>  { <span class="keywordflow">return</span> !__rhs || !(__lhs == *__rhs); }</div><div class="line"><a name="l00927"></a><span class="lineno"> 927</span> </div><div class="line"><a name="l00928"></a><span class="lineno"> 928</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00929"></a><span class="lineno"> 929</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00930"></a><span class="lineno"> 930</span>  operator<(<span class="keyword">const</span> optional<_Tp>& __lhs, <span class="keyword">const</span> _Tp& __rhs)</div><div class="line"><a name="l00931"></a><span class="lineno"> 931</span>  { <span class="keywordflow">return</span> !__lhs || *__lhs < __rhs; }</div><div class="line"><a name="l00932"></a><span class="lineno"> 932</span> </div><div class="line"><a name="l00933"></a><span class="lineno"> 933</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00934"></a><span class="lineno"> 934</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00935"></a><span class="lineno"> 935</span>  operator<(<span class="keyword">const</span> _Tp& __lhs, <span class="keyword">const</span> optional<_Tp>& __rhs)</div><div class="line"><a name="l00936"></a><span class="lineno"> 936</span>  { <span class="keywordflow">return</span> __rhs && __lhs < *__rhs; }</div><div class="line"><a name="l00937"></a><span class="lineno"> 937</span> </div><div class="line"><a name="l00938"></a><span class="lineno"> 938</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00939"></a><span class="lineno"> 939</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00940"></a><span class="lineno"> 940</span>  operator>(<span class="keyword">const</span> optional<_Tp>& __lhs, <span class="keyword">const</span> _Tp& __rhs)</div><div class="line"><a name="l00941"></a><span class="lineno"> 941</span>  { <span class="keywordflow">return</span> __lhs && __rhs < *__lhs; }</div><div class="line"><a name="l00942"></a><span class="lineno"> 942</span> </div><div class="line"><a name="l00943"></a><span class="lineno"> 943</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00944"></a><span class="lineno"> 944</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00945"></a><span class="lineno"> 945</span>  operator>(<span class="keyword">const</span> _Tp& __lhs, <span class="keyword">const</span> optional<_Tp>& __rhs)</div><div class="line"><a name="l00946"></a><span class="lineno"> 946</span>  { <span class="keywordflow">return</span> !__rhs || *__rhs < __lhs; }</div><div class="line"><a name="l00947"></a><span class="lineno"> 947</span> </div><div class="line"><a name="l00948"></a><span class="lineno"> 948</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00949"></a><span class="lineno"> 949</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00950"></a><span class="lineno"> 950</span>  operator<=(<span class="keyword">const</span> optional<_Tp>& __lhs, <span class="keyword">const</span> _Tp& __rhs)</div><div class="line"><a name="l00951"></a><span class="lineno"> 951</span>  { <span class="keywordflow">return</span> !__lhs || !(__rhs < *__lhs); }</div><div class="line"><a name="l00952"></a><span class="lineno"> 952</span> </div><div class="line"><a name="l00953"></a><span class="lineno"> 953</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00954"></a><span class="lineno"> 954</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00955"></a><span class="lineno"> 955</span>  operator<=(<span class="keyword">const</span> _Tp& __lhs, <span class="keyword">const</span> optional<_Tp>& __rhs)</div><div class="line"><a name="l00956"></a><span class="lineno"> 956</span>  { <span class="keywordflow">return</span> __rhs && !(*__rhs < __lhs); }</div><div class="line"><a name="l00957"></a><span class="lineno"> 957</span> </div><div class="line"><a name="l00958"></a><span class="lineno"> 958</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00959"></a><span class="lineno"> 959</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00960"></a><span class="lineno"> 960</span>  operator>=(<span class="keyword">const</span> optional<_Tp>& __lhs, <span class="keyword">const</span> _Tp& __rhs)</div><div class="line"><a name="l00961"></a><span class="lineno"> 961</span>  { <span class="keywordflow">return</span> __lhs && !(*__lhs < __rhs); }</div><div class="line"><a name="l00962"></a><span class="lineno"> 962</span> </div><div class="line"><a name="l00963"></a><span class="lineno"> 963</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00964"></a><span class="lineno"> 964</span>  constexpr <span class="keywordtype">bool</span></div><div class="line"><a name="l00965"></a><span class="lineno"> 965</span>  operator>=(<span class="keyword">const</span> _Tp& __lhs, <span class="keyword">const</span> optional<_Tp>& __rhs)</div><div class="line"><a name="l00966"></a><span class="lineno"> 966</span>  { <span class="keywordflow">return</span> !__rhs || !(__lhs < *__rhs); }</div><div class="line"><a name="l00967"></a><span class="lineno"> 967</span> </div><div class="line"><a name="l00968"></a><span class="lineno"> 968</span>  <span class="comment">// [X.Y.11]</span></div><div class="line"><a name="l00969"></a><span class="lineno"> 969</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00970"></a><span class="lineno"> 970</span>  <span class="keyword">inline</span> <span class="keywordtype">void</span></div><div class="line"><a name="l00971"></a><span class="lineno"> 971</span>  swap(optional<_Tp>& __lhs, optional<_Tp>& __rhs)</div><div class="line"><a name="l00972"></a><span class="lineno"> 972</span>  noexcept(noexcept(__lhs.swap(__rhs)))</div><div class="line"><a name="l00973"></a><span class="lineno"> 973</span>  { __lhs.swap(__rhs); }</div><div class="line"><a name="l00974"></a><span class="lineno"> 974</span> </div><div class="line"><a name="l00975"></a><span class="lineno"> 975</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00976"></a><span class="lineno"> 976</span>  constexpr optional<decay_t<_Tp>></div><div class="line"><a name="l00977"></a><span class="lineno"> 977</span>  make_optional(_Tp&& __t)</div><div class="line"><a name="l00978"></a><span class="lineno"> 978</span>  { <span class="keywordflow">return</span> optional<decay_t<_Tp>> { std::forward<_Tp>(__t) }; }</div><div class="line"><a name="l00979"></a><span class="lineno"> 979</span> </div><div class="line"><a name="l00980"></a><span class="lineno"> 980</span>  <span class="comment">// @} group optional</span></div><div class="line"><a name="l00981"></a><span class="lineno"> 981</span> } <span class="comment">// namespace fundamentals_v1</span></div><div class="line"><a name="l00982"></a><span class="lineno"> 982</span> } <span class="comment">// namespace experimental</span></div><div class="line"><a name="l00983"></a><span class="lineno"> 983</span> </div><div class="line"><a name="l00984"></a><span class="lineno"> 984</span>  <span class="comment">// [X.Y.12]</span></div><div class="line"><a name="l00985"></a><span class="lineno"> 985</span>  <span class="keyword">template</span><<span class="keyword">typename</span> _Tp></div><div class="line"><a name="l00986"></a><span class="lineno"> 986</span>  <span class="keyword">struct </span>hash<experimental::optional<_Tp>></div><div class="line"><a name="l00987"></a><span class="lineno"> 987</span>  {</div><div class="line"><a name="l00988"></a><span class="lineno"> 988</span>  <span class="keyword">using</span> result_type = size_t;</div><div class="line"><a name="l00989"></a><span class="lineno"> 989</span>  <span class="keyword">using</span> argument_type = experimental::optional<_Tp>;</div><div class="line"><a name="l00990"></a><span class="lineno"> 990</span> </div><div class="line"><a name="l00991"></a><span class="lineno"> 991</span>  <span class="keywordtype">size_t</span></div><div class="line"><a name="l00992"></a><span class="lineno"> 992</span>  operator()(<span class="keyword">const</span> experimental::optional<_Tp>& __t) <span class="keyword">const</span></div><div class="line"><a name="l00993"></a><span class="lineno"> 993</span>  noexcept(noexcept(hash<_Tp> {}(*__t)))</div><div class="line"><a name="l00994"></a><span class="lineno"> 994</span>  {</div><div class="line"><a name="l00995"></a><span class="lineno"> 995</span>  <span class="comment">// We pick an arbitrary hash for disengaged optionals which hopefully</span></div><div class="line"><a name="l00996"></a><span class="lineno"> 996</span>  <span class="comment">// usual values of _Tp won't typically hash to.</span></div><div class="line"><a name="l00997"></a><span class="lineno"> 997</span>  constexpr <span class="keywordtype">size_t</span> __magic_disengaged_hash = static_cast<size_t>(-3333);</div><div class="line"><a name="l00998"></a><span class="lineno"> 998</span>  <span class="keywordflow">return</span> __t ? hash<_Tp> {}(*__t) : __magic_disengaged_hash;</div><div class="line"><a name="l00999"></a><span class="lineno"> 999</span>  }</div><div class="line"><a name="l01000"></a><span class="lineno"> 1000</span>  };</div><div class="line"><a name="l01001"></a><span class="lineno"> 1001</span> </div><div class="line"><a name="l01002"></a><span class="lineno"> 1002</span> _GLIBCXX_END_NAMESPACE_VERSION</div><div class="line"><a name="l01003"></a><span class="lineno"> 1003</span> } <span class="comment">// namespace std</span></div><div class="line"><a name="l01004"></a><span class="lineno"> 1004</span> </div><div class="line"><a name="l01005"></a><span class="lineno"> 1005</span> <span class="preprocessor">#endif // C++14</span></div><div class="line"><a name="l01006"></a><span class="lineno"> 1006</span> </div><div class="line"><a name="l01007"></a><span class="lineno"> 1007</span> <span class="preprocessor">#endif // _GLIBCXX_EXPERIMENTAL_OPTIONAL</span></div><div class="ttc" id="a01515_html_ga2221e221b29838a39e88d176b5859900"><div class="ttname"><a href="a01515.html#ga2221e221b29838a39e88d176b5859900">std::experimental::fundamentals_v1::nullopt</a></div><div class="ttdeci">constexpr nullopt_t nullopt</div><div class="ttdoc">Tag to disengage optional objects.</div><div class="ttdef"><b>Definition:</b> <a href="a01007_source.html#l00107">optional:107</a></div></div>
<div class="ttc" id="a03848_html"><div class="ttname"><a href="a03848.html">std::is_trivially_destructible</a></div><div class="ttdoc">is_trivially_destructible</div><div class="ttdef"><b>Definition:</b> <a href="a00167_source.html#l01229">type_traits:1229</a></div></div>
<div class="ttc" id="a17211_html"><div class="ttname"><a href="a17211.html">type_traits</a></div></div>
<div class="ttc" id="a01515_html_ga69b3880c858acc1b7f88478d209b2fb3"><div class="ttname"><a href="a01515.html#ga69b3880c858acc1b7f88478d209b2fb3">std::experimental::fundamentals_v1::in_place</a></div><div class="ttdeci">constexpr in_place_t in_place</div><div class="ttdoc">Tag for in-place construction.</div><div class="ttdef"><b>Definition:</b> <a href="a01007_source.html#l00088">optional:88</a></div></div>
<div class="ttc" id="a00356_html"><div class="ttname"><a href="a00356.html">functexcept.h</a></div></div>
<div class="ttc" id="a10000_html"><div class="ttname"><a href="a10000.html">std::experimental::fundamentals_v1::bad_optional_access</a></div><div class="ttdoc">Exception class thrown when a disengaged optional object is dereferenced.</div><div class="ttdef"><b>Definition:</b> <a href="a01007_source.html#l00115">optional:115</a></div></div>
<div class="ttc" id="a09988_html"><div class="ttname"><a href="a09988.html">std::experimental::fundamentals_v1::optional</a></div><div class="ttdoc">Class template for optional values.</div><div class="ttdef"><b>Definition:</b> <a href="a01007_source.html#l00081">optional:81</a></div></div>
<div class="ttc" id="a00359_html"><div class="ttname"><a href="a00359.html">functional_hash.h</a></div></div>
<div class="ttc" id="a10020_html"><div class="ttname"><a href="a10020.html">std::experimental::fundamentals_v1::_Has_addressof</a></div><div class="ttdoc">Trait that detects the presence of an overloaded unary operator&.</div><div class="ttdef"><b>Definition:</b> <a href="a01007_source.html#l00162">optional:162</a></div></div>
<div class="ttc" id="a03644_html"><div class="ttname"><a href="a03644.html">std::is_nothrow_constructible</a></div><div class="ttdoc">is_nothrow_constructible</div><div class="ttdef"><b>Definition:</b> <a href="a00167_source.html#l00963">type_traits:963</a></div></div>
<div class="ttc" id="a09996_html"><div class="ttname"><a href="a09996.html">std::experimental::fundamentals_v1::nullopt_t</a></div><div class="ttdoc">Tag type to disengage optional objects.</div><div class="ttdef"><b>Definition:</b> <a href="a01007_source.html#l00092">optional:92</a></div></div>
<div class="ttc" id="a00323_html"><div class="ttname"><a href="a00323.html">enable_special_members.h</a></div></div>
<div class="ttc" id="a03676_html"><div class="ttname"><a href="a03676.html">std::is_nothrow_move_constructible</a></div><div class="ttdoc">is_nothrow_move_constructible</div><div class="ttdef"><b>Definition:</b> <a href="a00167_source.html#l01000">type_traits:1000</a></div></div>
<div class="ttc" id="a03396_html"><div class="ttname"><a href="a03396.html">std::is_reference</a></div><div class="ttdoc">is_reference</div><div class="ttdef"><b>Definition:</b> <a href="a00167_source.html#l00568">type_traits:568</a></div></div>
<div class="ttc" id="a01477_html_ga1954d5552e24586051011312041033f6"><div class="ttname"><a href="a01477.html#ga1954d5552e24586051011312041033f6">std::__addressof</a></div><div class="ttdeci">constexpr _Tp * __addressof(_Tp &__r) noexcept</div><div class="ttdoc">Same as C++11 std::addressof.</div><div class="ttdef"><b>Definition:</b> <a href="a00422_source.html#l00047">move.h:47</a></div></div>
<div class="ttc" id="a01477_html_gacb5baec338e12b99cb6bddea7506c7c6"><div class="ttname"><a href="a01477.html#gacb5baec338e12b99cb6bddea7506c7c6">std::forward</a></div><div class="ttdeci">constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept</div><div class="ttdoc">Forward an lvalue.</div><div class="ttdef"><b>Definition:</b> <a href="a00422_source.html#l00074">move.h:74</a></div></div>
<div class="ttc" id="a02784_html_a48e6f223bbd547dcea0d5efdb54b4951"><div class="ttname"><a href="a02784.html#a48e6f223bbd547dcea0d5efdb54b4951">std::logic_error::logic_error</a></div><div class="ttdeci">logic_error(const string &__arg) _GLIBCXX_TXN_SAFE</div></div>
<div class="ttc" id="a02784_html"><div class="ttname"><a href="a02784.html">std::logic_error</a></div><div class="ttdoc">One of two subclasses of exception.</div><div class="ttdef"><b>Definition:</b> <a href="a00146_source.html#l00113">stdexcept:113</a></div></div>
<div class="ttc" id="a01515_html_gaec6098e9e49d3b1918c5de29086aeead"><div class="ttname"><a href="a01515.html#gaec6098e9e49d3b1918c5de29086aeead">std::experimental::fundamentals_v1::__constexpr_addressof</a></div><div class="ttdeci">constexpr enable_if_t<!_Has_addressof< _Tp >::value, _Tp * > __constexpr_addressof(_Tp &__t)</div><div class="ttdoc">An overload that attempts to take the address of an lvalue as a constant expression....</div><div class="ttdef"><b>Definition:</b> <a href="a01007_source.html#l00175">optional:175</a></div></div>
<div class="ttc" id="a00995_html"><div class="ttname"><a href="a00995.html">lfts_config.h</a></div></div>
<div class="ttc" id="a00029_html"><div class="ttname"><a href="a00029.html">initializer_list</a></div></div>
<div class="ttc" id="a00146_html"><div class="ttname"><a href="a00146.html">stdexcept</a></div></div>
<div class="ttc" id="a01538_html"><div class="ttname"><a href="a01538.html">std</a></div><div class="ttdoc">ISO C++ entities toplevel namespace is std.</div></div>
<div class="ttc" id="a01476_html_gabe26c12710bb4c683badfaf0a586c5be"><div class="ttname"><a href="a01476.html#gabe26c12710bb4c683badfaf0a586c5be">std::decay_t</a></div><div class="ttdeci">typename decay< _Tp >::type decay_t</div><div class="ttdoc">Alias template for decay.</div><div class="ttdef"><b>Definition:</b> <a href="a00167_source.html#l02290">type_traits:2290</a></div></div>
<div class="ttc" id="a00032_html"><div class="ttname"><a href="a00032.html">new</a></div></div>
<div class="ttc" id="a10024_html"><div class="ttname"><a href="a10024.html">std::experimental::fundamentals_v1::_Optional_base</a></div><div class="ttdoc">Class template that holds the necessary state for Optional values and that has the responsibility for...</div><div class="ttdef"><b>Definition:</b> <a href="a01007_source.html#l00202">optional:202</a></div></div>
<div class="ttc" id="a03900_html"><div class="ttname"><a href="a03900.html">std::is_convertible</a></div><div class="ttdoc">is_convertible</div><div class="ttdef"><b>Definition:</b> <a href="a00167_source.html#l01327">type_traits:1327</a></div></div>
<div class="ttc" id="a01476_html_ga4e79124b56e4ce8037d87387898b9d1f"><div class="ttname"><a href="a01476.html#ga4e79124b56e4ce8037d87387898b9d1f">std::remove_const_t</a></div><div class="ttdeci">typename remove_const< _Tp >::type remove_const_t</div><div class="ttdoc">Alias template for remove_const.</div><div class="ttdef"><b>Definition:</b> <a href="a00167_source.html#l01384">type_traits:1384</a></div></div>
<div class="ttc" id="a01476_html_gaccc2a55dff256e901d69f67ef213d12c"><div class="ttname"><a href="a01476.html#gaccc2a55dff256e901d69f67ef213d12c">std::enable_if_t</a></div><div class="ttdeci">typename enable_if< _Cond, _Tp >::type enable_if_t</div><div class="ttdoc">Alias template for enable_if.</div><div class="ttdef"><b>Definition:</b> <a href="a00167_source.html#l02294">type_traits:2294</a></div></div>
<div class="ttc" id="a03752_html"><div class="ttname"><a href="a03752.html">std::is_nothrow_move_assignable</a></div><div class="ttdoc">is_nothrow_move_assignable</div><div class="ttdef"><b>Definition:</b> <a href="a00167_source.html#l01090">type_traits:1090</a></div></div>
<div class="ttc" id="a03040_html"><div class="ttname"><a href="a03040.html">std::integral_constant</a></div><div class="ttdoc">integral_constant</div><div class="ttdef"><b>Definition:</b> <a href="a00167_source.html#l00057">type_traits:57</a></div></div>
<div class="ttc" id="a05348_html"><div class="ttname"><a href="a05348.html">std::_Enable_copy_move</a></div><div class="ttdoc">A mixin helper to conditionally enable or disable the copy/move special members.</div><div class="ttdef"><b>Definition:</b> <a href="a00323_source.html#l00084">enable_special_members.h:84</a></div></div>
<div class="ttc" id="a09992_html"><div class="ttname"><a href="a09992.html">std::experimental::fundamentals_v1::in_place_t</a></div><div class="ttdoc">Tag type for in-place construction.</div><div class="ttdef"><b>Definition:</b> <a href="a01007_source.html#l00085">optional:85</a></div></div>
<div class="ttc" id="a01652_html"><div class="ttname"><a href="a01652.html">std::initializer_list</a></div><div class="ttdoc">initializer_list</div><div class="ttdef"><b>Definition:</b> <a href="a00029_source.html#l00047">initializer_list:47</a></div></div>
<div class="ttc" id="a03572_html"><div class="ttname"><a href="a03572.html">std::is_constructible</a></div><div class="ttdoc">is_constructible</div><div class="ttdef"><b>Definition:</b> <a href="a00167_source.html#l00872">type_traits:872</a></div></div>
<div class="ttc" id="a17232_html"><div class="ttname"><a href="a17232.html">utility</a></div></div>
<div class="ttc" id="a03880_html"><div class="ttname"><a href="a03880.html">std::is_same</a></div><div class="ttdoc">is_same</div><div class="ttdef"><b>Definition:</b> <a href="a00167_source.html#l01286">type_traits:1286</a></div></div>
<div class="ttc" id="a01476_html_ga33d8994a84545d04adc29f8be0d12122"><div class="ttname"><a href="a01476.html#ga33d8994a84545d04adc29f8be0d12122">std::remove_cv_t</a></div><div class="ttdeci">typename remove_cv< _Tp >::type remove_cv_t</div><div class="ttdoc">Alias template for remove_cv.</div><div class="ttdef"><b>Definition:</b> <a href="a00167_source.html#l01392">type_traits:1392</a></div></div>
<div class="ttc" id="a03680_html"><div class="ttname"><a href="a03680.html">std::is_assignable</a></div><div class="ttdoc">is_assignable</div><div class="ttdef"><b>Definition:</b> <a href="a00167_source.html#l01006">type_traits:1006</a></div></div>
</div><!-- fragment --></div><!-- contents -->
</div><!-- doc-content -->
<!-- start footer part -->
<div id="nav-path" class="navpath"><!-- id is needed for treeview function! -->
<ul>
<li class="navelem"><a class="el" href="dir_3a83f109ff04170a1f8448445d1bdcba.html">include</a></li><li class="navelem"><a class="el" href="dir_70d4ab3a5261b72adc47eec15b413144.html">experimental</a></li><li class="navelem"><a class="el" href="a01007.html">optional</a></li>
<li class="footer">Generated by
<a href="http://www.doxygen.org/index.html">
<img class="footer" src="doxygen.png" alt="doxygen"/></a> 1.8.15 </li>
</ul>
</div>
</body>
</html>
