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<li class="navelem"><a class="el" href="dir_8cab8f464681f7cc51cee77e79a434cd.html">3rdparty</a></li><li class="navelem"><a class="el" href="dir_82e31a22178767beedddc7597fd1ecb6.html">dmlc-core</a></li><li class="navelem"><a class="el" href="dir_7dd5b88db83ff474628c03c453739a90.html">include</a></li><li class="navelem"><a class="el" href="dir_e30967e3ab51f65ad4b50dd298ccf4e7.html">dmlc</a></li> </ul>
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<a href="optional_8h.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span>&#160;</div><div class="line"><a name="l00006"></a><span class="lineno"> 6</span>&#160;<span class="preprocessor">#ifndef DMLC_OPTIONAL_H_</span></div><div class="line"><a name="l00007"></a><span class="lineno"> 7</span>&#160;<span class="preprocessor">#define DMLC_OPTIONAL_H_</span></div><div class="line"><a name="l00008"></a><span class="lineno"> 8</span>&#160;</div><div class="line"><a name="l00009"></a><span class="lineno"> 9</span>&#160;<span class="preprocessor">#include &lt;iostream&gt;</span></div><div class="line"><a name="l00010"></a><span class="lineno"> 10</span>&#160;<span class="preprocessor">#include &lt;string&gt;</span></div><div class="line"><a name="l00011"></a><span class="lineno"> 11</span>&#160;<span class="preprocessor">#include &lt;utility&gt;</span></div><div class="line"><a name="l00012"></a><span class="lineno"> 12</span>&#160;<span class="preprocessor">#include &lt;algorithm&gt;</span></div><div class="line"><a name="l00013"></a><span class="lineno"> 13</span>&#160;</div><div class="line"><a name="l00014"></a><span class="lineno"> 14</span>&#160;<span class="preprocessor">#include &quot;<a class="code" href="3rdparty_2dmlc-core_2include_2dmlc_2base_8h.html">./base.h</a>&quot;</span></div><div class="line"><a name="l00015"></a><span class="lineno"> 15</span>&#160;<span class="preprocessor">#include &quot;<a class="code" href="common_8h.html">./common.h</a>&quot;</span></div><div class="line"><a name="l00016"></a><span class="lineno"> 16</span>&#160;<span class="preprocessor">#include &quot;./logging.h&quot;</span></div><div class="line"><a name="l00017"></a><span class="lineno"> 17</span>&#160;<span class="preprocessor">#include &quot;<a class="code" href="type__traits_8h.html">./type_traits.h</a>&quot;</span></div><div class="line"><a name="l00018"></a><span class="lineno"> 18</span>&#160;</div><div class="line"><a name="l00019"></a><span class="lineno"> 19</span>&#160;<span class="keyword">namespace </span><a class="code" href="namespacedmlc.html">dmlc</a> {</div><div class="line"><a name="l00020"></a><span class="lineno"> 20</span>&#160;</div><div class="line"><a name="l00022"></a><span class="lineno"><a class="line" href="structdmlc_1_1nullopt__t.html"> 22</a></span>&#160;<span class="keyword">struct </span><a class="code" href="structdmlc_1_1nullopt__t.html">nullopt_t</a> {</div><div class="line"><a name="l00023"></a><span class="lineno"> 23</span>&#160;<span class="preprocessor">#if defined(_MSC_VER) &amp;&amp; _MSC_VER &lt; 1900</span></div><div class="line"><a name="l00024"></a><span class="lineno"> 24</span>&#160;</div><div class="line"><a name="l00025"></a><span class="lineno"> 25</span>&#160; <span class="keyword">explicit</span> <a class="code" href="structdmlc_1_1nullopt__t.html#a0d5231f7d348cbab57afe3f4b601b51d">nullopt_t</a>(<span class="keywordtype">int</span> a) {}</div><div class="line"><a name="l00026"></a><span class="lineno"> 26</span>&#160;<span class="preprocessor">#else</span></div><div class="line"><a name="l00027"></a><span class="lineno"> 27</span>&#160;</div><div class="line"><a name="l00028"></a><span class="lineno"><a class="line" href="structdmlc_1_1nullopt__t.html#a0d5231f7d348cbab57afe3f4b601b51d"> 28</a></span>&#160; constexpr <span class="keyword">explicit</span> <a class="code" href="structdmlc_1_1nullopt__t.html#a0d5231f7d348cbab57afe3f4b601b51d">nullopt_t</a>(<span class="keywordtype">int</span> a) {}</div><div class="line"><a name="l00029"></a><span class="lineno"> 29</span>&#160;<span class="preprocessor">#endif</span></div><div class="line"><a name="l00030"></a><span class="lineno"> 30</span>&#160;};</div><div class="line"><a name="l00031"></a><span class="lineno"> 31</span>&#160;</div><div class="line"><a name="l00033"></a><span class="lineno"><a class="line" href="namespacedmlc.html#a7e0f62af45e67c3b6fa22080e756b379"> 33</a></span>&#160;constexpr <span class="keyword">const</span> <a class="code" href="structdmlc_1_1nullopt__t.html">nullopt_t</a> <a class="code" href="namespacedmlc.html#a7e0f62af45e67c3b6fa22080e756b379">nullopt</a> = <a class="code" href="structdmlc_1_1nullopt__t.html#a0d5231f7d348cbab57afe3f4b601b51d">nullopt_t</a>(0);</div><div class="line"><a name="l00034"></a><span class="lineno"> 34</span>&#160;</div><div class="line"><a name="l00042"></a><span class="lineno"> 42</span>&#160;<span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div><div class="line"><a name="l00043"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html"> 43</a></span>&#160;<span class="keyword">class </span><a class="code" href="classdmlc_1_1optional.html">optional</a> {</div><div class="line"><a name="l00044"></a><span class="lineno"> 44</span>&#160; <span class="keyword">public</span>:</div><div class="line"><a name="l00046"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html#a358bf8befa660e58c07856b06c2e2b41"> 46</a></span>&#160; <a class="code" href="classdmlc_1_1optional.html#a358bf8befa660e58c07856b06c2e2b41">optional</a>() : is_none(true) {}</div><div class="line"><a name="l00048"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html#ad8d39fd99191c6f232063b60a1b7bb6f"> 48</a></span>&#160; <span class="keyword">explicit</span> <a class="code" href="classdmlc_1_1optional.html#ad8d39fd99191c6f232063b60a1b7bb6f">optional</a>(<span class="keyword">const</span> T&amp; value) {</div><div class="line"><a name="l00049"></a><span class="lineno"> 49</span>&#160;<span class="preprocessor">#pragma GCC diagnostic push</span></div><div class="line"><a name="l00050"></a><span class="lineno"> 50</span>&#160;<span class="preprocessor">#if __GNUC__ &gt;= 6</span></div><div class="line"><a name="l00051"></a><span class="lineno"> 51</span>&#160;<span class="preprocessor">#pragma GCC diagnostic ignored &quot;-Wmaybe-uninitialized&quot;</span></div><div class="line"><a name="l00052"></a><span class="lineno"> 52</span>&#160;<span class="preprocessor">#endif</span></div><div class="line"><a name="l00053"></a><span class="lineno"> 53</span>&#160; is_none = <span class="keyword">false</span>;</div><div class="line"><a name="l00054"></a><span class="lineno"> 54</span>&#160; <span class="keyword">new</span> (&amp;val) T(value);</div><div class="line"><a name="l00055"></a><span class="lineno"> 55</span>&#160;<span class="preprocessor">#pragma GCC diagnostic pop</span></div><div class="line"><a name="l00056"></a><span class="lineno"> 56</span>&#160; }</div><div class="line"><a name="l00058"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html#a0a0f99e2ba48f2583f164c2286dacc58"> 58</a></span>&#160; <a class="code" href="classdmlc_1_1optional.html#a0a0f99e2ba48f2583f164c2286dacc58">optional</a>(<span class="keyword">const</span> <a class="code" href="classdmlc_1_1optional.html">optional&lt;T&gt;</a>&amp; other) {</div><div class="line"><a name="l00059"></a><span class="lineno"> 59</span>&#160;<span class="preprocessor">#pragma GCC diagnostic push</span></div><div class="line"><a name="l00060"></a><span class="lineno"> 60</span>&#160;<span class="preprocessor">#if __GNUC__ &gt;= 6</span></div><div class="line"><a name="l00061"></a><span class="lineno"> 61</span>&#160;<span class="preprocessor">#pragma GCC diagnostic ignored &quot;-Wmaybe-uninitialized&quot;</span></div><div class="line"><a name="l00062"></a><span class="lineno"> 62</span>&#160;<span class="preprocessor">#endif</span></div><div class="line"><a name="l00063"></a><span class="lineno"> 63</span>&#160; is_none = other.is_none;</div><div class="line"><a name="l00064"></a><span class="lineno"> 64</span>&#160; <span class="keywordflow">if</span> (!is_none) {</div><div class="line"><a name="l00065"></a><span class="lineno"> 65</span>&#160; <span class="keyword">new</span> (&amp;val) T(other.<a class="code" href="classdmlc_1_1optional.html#aaf22cb65a584841e054aa69e4acdd0be">value</a>());</div><div class="line"><a name="l00066"></a><span class="lineno"> 66</span>&#160; }</div><div class="line"><a name="l00067"></a><span class="lineno"> 67</span>&#160;<span class="preprocessor">#pragma GCC diagnostic pop</span></div><div class="line"><a name="l00068"></a><span class="lineno"> 68</span>&#160; }</div><div class="line"><a name="l00070"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html#aacd056f3191890afa191f8ad50ebf27f"> 70</a></span>&#160; <a class="code" href="classdmlc_1_1optional.html#aacd056f3191890afa191f8ad50ebf27f">~optional</a>() {</div><div class="line"><a name="l00071"></a><span class="lineno"> 71</span>&#160; <span class="keywordflow">if</span> (!is_none) {</div><div class="line"><a name="l00072"></a><span class="lineno"> 72</span>&#160; <span class="keyword">reinterpret_cast&lt;</span>T*<span class="keyword">&gt;</span>(&amp;val)-&gt;~T();</div><div class="line"><a name="l00073"></a><span class="lineno"> 73</span>&#160; }</div><div class="line"><a name="l00074"></a><span class="lineno"> 74</span>&#160; }</div><div class="line"><a name="l00076"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html#aca79e391f4df7aaca345d05ae65a4d16"> 76</a></span>&#160; <span class="keywordtype">void</span> <a class="code" href="classdmlc_1_1optional.html#aca79e391f4df7aaca345d05ae65a4d16">swap</a>(<a class="code" href="classdmlc_1_1optional.html">optional&lt;T&gt;</a>&amp; other) {</div><div class="line"><a name="l00077"></a><span class="lineno"> 77</span>&#160; std::swap(val, other.val);</div><div class="line"><a name="l00078"></a><span class="lineno"> 78</span>&#160; std::swap(is_none, other.is_none);</div><div class="line"><a name="l00079"></a><span class="lineno"> 79</span>&#160; }</div><div class="line"><a name="l00084"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html#ab7b4fba71d2e988cd5dacb99a5da315e"> 84</a></span>&#160; <a class="code" href="classdmlc_1_1optional.html">optional&lt;T&gt;</a>&amp; <a class="code" href="classdmlc_1_1optional.html#ab7b4fba71d2e988cd5dacb99a5da315e">operator=</a>(<span class="keyword">const</span> T&amp; value) {</div><div class="line"><a name="l00085"></a><span class="lineno"> 85</span>&#160; (<a class="code" href="classdmlc_1_1optional.html">optional&lt;T&gt;</a>(value)).swap(*<span class="keyword">this</span>);</div><div class="line"><a name="l00086"></a><span class="lineno"> 86</span>&#160; <span class="keywordflow">return</span> *<span class="keyword">this</span>;</div><div class="line"><a name="l00087"></a><span class="lineno"> 87</span>&#160; }</div><div class="line"><a name="l00092"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html#a535a725a80a78681d96feac82c3f5110"> 92</a></span>&#160; <a class="code" href="classdmlc_1_1optional.html">optional&lt;T&gt;</a>&amp; <a class="code" href="classdmlc_1_1optional.html#a535a725a80a78681d96feac82c3f5110">operator=</a>(<span class="keyword">const</span> <a class="code" href="classdmlc_1_1optional.html">optional&lt;T&gt;</a> &amp;other) {</div><div class="line"><a name="l00093"></a><span class="lineno"> 93</span>&#160; (<a class="code" href="classdmlc_1_1optional.html">optional&lt;T&gt;</a>(other)).swap(*<span class="keyword">this</span>);</div><div class="line"><a name="l00094"></a><span class="lineno"> 94</span>&#160; <span class="keywordflow">return</span> *<span class="keyword">this</span>;</div><div class="line"><a name="l00095"></a><span class="lineno"> 95</span>&#160; }</div><div class="line"><a name="l00099"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html#ad2959fc0d19a5e4affbc9e1cd67e57ae"> 99</a></span>&#160; <a class="code" href="classdmlc_1_1optional.html">optional&lt;T&gt;</a>&amp; <a class="code" href="classdmlc_1_1optional.html#ad2959fc0d19a5e4affbc9e1cd67e57ae">operator=</a>(<a class="code" href="structdmlc_1_1nullopt__t.html">nullopt_t</a>) {</div><div class="line"><a name="l00100"></a><span class="lineno"> 100</span>&#160; (<a class="code" href="classdmlc_1_1optional.html">optional&lt;T&gt;</a>()).swap(*<span class="keyword">this</span>);</div><div class="line"><a name="l00101"></a><span class="lineno"> 101</span>&#160; <span class="keywordflow">return</span> *<span class="keyword">this</span>;</div><div class="line"><a name="l00102"></a><span class="lineno"> 102</span>&#160; }</div><div class="line"><a name="l00104"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html#a5df5732afa850c13c880db0db96c2702"> 104</a></span>&#160; T&amp; <a class="code" href="classdmlc_1_1optional.html#a5df5732afa850c13c880db0db96c2702">operator*</a>() { <span class="comment">// NOLINT(*)</span></div><div class="line"><a name="l00105"></a><span class="lineno"> 105</span>&#160; <span class="keywordflow">return</span> *<span class="keyword">reinterpret_cast&lt;</span>T*<span class="keyword">&gt;</span>(&amp;val);</div><div class="line"><a name="l00106"></a><span class="lineno"> 106</span>&#160; }</div><div class="line"><a name="l00108"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html#a0a8ba8634870786f4c8520b82550f57f"> 108</a></span>&#160; <span class="keyword">const</span> T&amp; <a class="code" href="classdmlc_1_1optional.html#a0a8ba8634870786f4c8520b82550f57f">operator*</a>()<span class="keyword"> const </span>{</div><div class="line"><a name="l00109"></a><span class="lineno"> 109</span>&#160; <span class="keywordflow">return</span> *<span class="keyword">reinterpret_cast&lt;</span><span class="keyword">const </span>T*<span class="keyword">&gt;</span>(&amp;val);</div><div class="line"><a name="l00110"></a><span class="lineno"> 110</span>&#160; }</div><div class="line"><a name="l00112"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html#a5c857b9eaf4721c111e3753cc7685cc0"> 112</a></span>&#160; <span class="keywordtype">bool</span> <a class="code" href="classdmlc_1_1optional.html#a5c857b9eaf4721c111e3753cc7685cc0">operator==</a>(<span class="keyword">const</span> <a class="code" href="classdmlc_1_1optional.html">optional&lt;T&gt;</a>&amp; other)<span class="keyword"> const </span>{</div><div class="line"><a name="l00113"></a><span class="lineno"> 113</span>&#160; <span class="keywordflow">return</span> this-&gt;is_none == other.is_none &amp;&amp;</div><div class="line"><a name="l00114"></a><span class="lineno"> 114</span>&#160; (this-&gt;is_none == <span class="keyword">true</span> || this-&gt;value() == other.<a class="code" href="classdmlc_1_1optional.html#aaf22cb65a584841e054aa69e4acdd0be">value</a>());</div><div class="line"><a name="l00115"></a><span class="lineno"> 115</span>&#160; }</div><div class="line"><a name="l00119"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html#aaf22cb65a584841e054aa69e4acdd0be"> 119</a></span>&#160; <span class="keyword">const</span> T&amp; <a class="code" href="classdmlc_1_1optional.html#aaf22cb65a584841e054aa69e4acdd0be">value</a>()<span class="keyword"> const </span>{</div><div class="line"><a name="l00120"></a><span class="lineno"> 120</span>&#160; <span class="keywordflow">if</span> (is_none) {</div><div class="line"><a name="l00121"></a><span class="lineno"> 121</span>&#160; <span class="keywordflow">throw</span> std::logic_error(<span class="stringliteral">&quot;bad optional access&quot;</span>);</div><div class="line"><a name="l00122"></a><span class="lineno"> 122</span>&#160; }</div><div class="line"><a name="l00123"></a><span class="lineno"> 123</span>&#160; <span class="keywordflow">return</span> *<span class="keyword">reinterpret_cast&lt;</span><span class="keyword">const </span>T*<span class="keyword">&gt;</span>(&amp;val);</div><div class="line"><a name="l00124"></a><span class="lineno"> 124</span>&#160; }</div><div class="line"><a name="l00126"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html#aeac40cbe8bcc4c6a5d582fe7a39bc146"> 126</a></span>&#160; <span class="keyword">explicit</span> <span class="keyword">operator</span> bool()<span class="keyword"> const </span>{ <span class="keywordflow">return</span> !is_none; }</div><div class="line"><a name="l00128"></a><span class="lineno"><a class="line" href="classdmlc_1_1optional.html#a0c135346d7c6425ce730493a89761c96"> 128</a></span>&#160; <span class="keywordtype">bool</span> <a class="code" href="classdmlc_1_1optional.html#a0c135346d7c6425ce730493a89761c96">has_value</a>()<span class="keyword"> const </span>{ <span class="keywordflow">return</span> <span class="keyword">operator</span> bool(); }</div><div class="line"><a name="l00129"></a><span class="lineno"> 129</span>&#160;</div><div class="line"><a name="l00130"></a><span class="lineno"> 130</span>&#160; <span class="keyword">private</span>:</div><div class="line"><a name="l00131"></a><span class="lineno"> 131</span>&#160; <span class="comment">// whether this is none</span></div><div class="line"><a name="l00132"></a><span class="lineno"> 132</span>&#160; <span class="keywordtype">bool</span> is_none;</div><div class="line"><a name="l00133"></a><span class="lineno"> 133</span>&#160; <span class="comment">// on stack storage of value</span></div><div class="line"><a name="l00134"></a><span class="lineno"> 134</span>&#160; <span class="keyword">typename</span> std::aligned_storage&lt;sizeof(T), alignof(T)&gt;::type val;</div><div class="line"><a name="l00135"></a><span class="lineno"> 135</span>&#160;};</div><div class="line"><a name="l00136"></a><span class="lineno"> 136</span>&#160;</div><div class="line"><a name="l00150"></a><span class="lineno"> 150</span>&#160;<span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div><div class="line"><a name="l00151"></a><span class="lineno"><a class="line" href="namespacedmlc.html#acf31f99192b5ed0d5d77398d58023912"> 151</a></span>&#160;std::ostream &amp;operator&lt;&lt;(std::ostream &amp;os, const optional&lt;T&gt; &amp;t) {</div><div class="line"><a name="l00152"></a><span class="lineno"> 152</span>&#160; <span class="keywordflow">if</span> (t) {</div><div class="line"><a name="l00153"></a><span class="lineno"> 153</span>&#160; os &lt;&lt; *t;</div><div class="line"><a name="l00154"></a><span class="lineno"> 154</span>&#160; } <span class="keywordflow">else</span> {</div><div class="line"><a name="l00155"></a><span class="lineno"> 155</span>&#160; os &lt;&lt; <span class="stringliteral">&quot;None&quot;</span>;</div><div class="line"><a name="l00156"></a><span class="lineno"> 156</span>&#160; }</div><div class="line"><a name="l00157"></a><span class="lineno"> 157</span>&#160; <span class="keywordflow">return</span> os;</div><div class="line"><a name="l00158"></a><span class="lineno"> 158</span>&#160;}</div><div class="line"><a name="l00159"></a><span class="lineno"> 159</span>&#160;</div><div class="line"><a name="l00177"></a><span class="lineno"> 177</span>&#160;<span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div><div class="line"><a name="l00178"></a><span class="lineno"><a class="line" href="namespacedmlc.html#acc4b71c13985425358cb63cc45d49512"> 178</a></span>&#160;std::istream &amp;<a class="code" href="namespacedmlc.html#acc4b71c13985425358cb63cc45d49512">operator&gt;&gt;</a>(std::istream &amp;is, <a class="code" href="classdmlc_1_1optional.html">optional&lt;T&gt;</a> &amp;t) {</div><div class="line"><a name="l00179"></a><span class="lineno"> 179</span>&#160; <span class="keywordtype">char</span> buf[4];</div><div class="line"><a name="l00180"></a><span class="lineno"> 180</span>&#160; std::streampos origin = is.tellg();</div><div class="line"><a name="l00181"></a><span class="lineno"> 181</span>&#160; is.read(buf, 4);</div><div class="line"><a name="l00182"></a><span class="lineno"> 182</span>&#160; <span class="keywordflow">if</span> (is.fail() || buf[0] != <span class="charliteral">&#39;N&#39;</span> || buf[1] != <span class="charliteral">&#39;o&#39;</span> ||</div><div class="line"><a name="l00183"></a><span class="lineno"> 183</span>&#160; buf[2] != <span class="charliteral">&#39;n&#39;</span> || buf[3] != <span class="charliteral">&#39;e&#39;</span>) {</div><div class="line"><a name="l00184"></a><span class="lineno"> 184</span>&#160; is.clear();</div><div class="line"><a name="l00185"></a><span class="lineno"> 185</span>&#160; is.seekg(origin);</div><div class="line"><a name="l00186"></a><span class="lineno"> 186</span>&#160; T x;</div><div class="line"><a name="l00187"></a><span class="lineno"> 187</span>&#160; is &gt;&gt; x;</div><div class="line"><a name="l00188"></a><span class="lineno"> 188</span>&#160; t = x;</div><div class="line"><a name="l00189"></a><span class="lineno"> 189</span>&#160; <span class="keywordflow">if</span> (std::is_integral&lt;T&gt;::value &amp;&amp; !is.eof() &amp;&amp; is.peek() == <span class="charliteral">&#39;L&#39;</span>) is.get();</div><div class="line"><a name="l00190"></a><span class="lineno"> 190</span>&#160; } <span class="keywordflow">else</span> {</div><div class="line"><a name="l00191"></a><span class="lineno"> 191</span>&#160; t = <a class="code" href="namespacedmlc.html#a7e0f62af45e67c3b6fa22080e756b379">nullopt</a>;</div><div class="line"><a name="l00192"></a><span class="lineno"> 192</span>&#160; }</div><div class="line"><a name="l00193"></a><span class="lineno"> 193</span>&#160; <span class="keywordflow">return</span> is;</div><div class="line"><a name="l00194"></a><span class="lineno"> 194</span>&#160;}</div><div class="line"><a name="l00215"></a><span class="lineno"><a class="line" href="namespacedmlc.html#a5018d09b0f92f75d2c3ee572f62c0346"> 215</a></span>&#160;<span class="keyword">inline</span> std::istream &amp;<a class="code" href="namespacedmlc.html#acc4b71c13985425358cb63cc45d49512">operator&gt;&gt;</a>(std::istream &amp;is, <a class="code" href="classdmlc_1_1optional.html">optional&lt;bool&gt;</a> &amp;t) {</div><div class="line"><a name="l00216"></a><span class="lineno"> 216</span>&#160; <span class="comment">// Discard initial whitespace</span></div><div class="line"><a name="l00217"></a><span class="lineno"> 217</span>&#160; <span class="keywordflow">while</span> (<a class="code" href="namespacedmlc.html#a52dcf01c9ba22be9b08e455194fb2ab3">isspace</a>(is.peek()))</div><div class="line"><a name="l00218"></a><span class="lineno"> 218</span>&#160; is.get();</div><div class="line"><a name="l00219"></a><span class="lineno"> 219</span>&#160; <span class="comment">// Extract chars that might be valid into a separate string, stopping</span></div><div class="line"><a name="l00220"></a><span class="lineno"> 220</span>&#160; <span class="comment">// on whitespace or other non-alphanumerics such as &quot;,)]&quot;.</span></div><div class="line"><a name="l00221"></a><span class="lineno"> 221</span>&#160; std::string s;</div><div class="line"><a name="l00222"></a><span class="lineno"> 222</span>&#160; <span class="keywordflow">while</span> (isalnum(is.peek()))</div><div class="line"><a name="l00223"></a><span class="lineno"> 223</span>&#160; s.push_back(is.get());</div><div class="line"><a name="l00224"></a><span class="lineno"> 224</span>&#160;</div><div class="line"><a name="l00225"></a><span class="lineno"> 225</span>&#160; <span class="keywordflow">if</span> (!is.fail()) {</div><div class="line"><a name="l00226"></a><span class="lineno"> 226</span>&#160; std::transform(s.begin(), s.end(), s.begin(), ::tolower);</div><div class="line"><a name="l00227"></a><span class="lineno"> 227</span>&#160; <span class="keywordflow">if</span> (s == <span class="stringliteral">&quot;1&quot;</span> || s == <span class="stringliteral">&quot;true&quot;</span>)</div><div class="line"><a name="l00228"></a><span class="lineno"> 228</span>&#160; t = <span class="keyword">true</span>;</div><div class="line"><a name="l00229"></a><span class="lineno"> 229</span>&#160; <span class="keywordflow">else</span> <span class="keywordflow">if</span> (s == <span class="stringliteral">&quot;0&quot;</span> || s == <span class="stringliteral">&quot;false&quot;</span>)</div><div class="line"><a name="l00230"></a><span class="lineno"> 230</span>&#160; t = <span class="keyword">false</span>;</div><div class="line"><a name="l00231"></a><span class="lineno"> 231</span>&#160; <span class="keywordflow">else</span> <span class="keywordflow">if</span> (s == <span class="stringliteral">&quot;none&quot;</span>)</div><div class="line"><a name="l00232"></a><span class="lineno"> 232</span>&#160; t = <a class="code" href="namespacedmlc.html#a7e0f62af45e67c3b6fa22080e756b379">nullopt</a>;</div><div class="line"><a name="l00233"></a><span class="lineno"> 233</span>&#160; <span class="keywordflow">else</span></div><div class="line"><a name="l00234"></a><span class="lineno"> 234</span>&#160; is.setstate(std::ios::failbit);</div><div class="line"><a name="l00235"></a><span class="lineno"> 235</span>&#160; }</div><div class="line"><a name="l00236"></a><span class="lineno"> 236</span>&#160;</div><div class="line"><a name="l00237"></a><span class="lineno"> 237</span>&#160; <span class="keywordflow">return</span> is;</div><div class="line"><a name="l00238"></a><span class="lineno"> 238</span>&#160;}</div><div class="line"><a name="l00239"></a><span class="lineno"> 239</span>&#160;</div><div class="line"><a name="l00241"></a><span class="lineno"> 241</span>&#160;<a class="code" href="namespacedmlc.html#ae0e0e4f86115e4c4e7f761de5c8a6797">DMLC_DECLARE_TYPE_NAME</a>(<a class="code" href="classdmlc_1_1optional.html">optional&lt;int&gt;</a>, <span class="stringliteral">&quot;int or None&quot;</span>);</div><div class="line"><a name="l00243"></a><span class="lineno"> 243</span>&#160;<a class="code" href="namespacedmlc.html#ae0e0e4f86115e4c4e7f761de5c8a6797">DMLC_DECLARE_TYPE_NAME</a>(<a class="code" href="classdmlc_1_1optional.html">optional&lt;bool&gt;</a>, <span class="stringliteral">&quot;boolean or None&quot;</span>);</div><div class="line"><a name="l00245"></a><span class="lineno"> 245</span>&#160;<a class="code" href="namespacedmlc.html#ae0e0e4f86115e4c4e7f761de5c8a6797">DMLC_DECLARE_TYPE_NAME</a>(<a class="code" href="classdmlc_1_1optional.html">optional&lt;float&gt;</a>, <span class="stringliteral">&quot;float or None&quot;</span>);</div><div class="line"><a name="l00247"></a><span class="lineno"> 247</span>&#160;<a class="code" href="namespacedmlc.html#ae0e0e4f86115e4c4e7f761de5c8a6797">DMLC_DECLARE_TYPE_NAME</a>(<a class="code" href="classdmlc_1_1optional.html">optional&lt;double&gt;</a>, <span class="stringliteral">&quot;double or None&quot;</span>);</div><div class="line"><a name="l00248"></a><span class="lineno"> 248</span>&#160;</div><div class="line"><a name="l00249"></a><span class="lineno"> 249</span>&#160;} <span class="comment">// namespace dmlc</span></div><div class="line"><a name="l00250"></a><span class="lineno"> 250</span>&#160;</div><div class="line"><a name="l00251"></a><span class="lineno"><a class="line" href="namespacestd.html"> 251</a></span>&#160;<span class="keyword">namespace </span><a class="code" href="namespacestd.html">std</a> {</div><div class="line"><a name="l00253"></a><span class="lineno"> 253</span>&#160;<span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div><div class="line"><a name="l00254"></a><span class="lineno"><a class="line" href="structstd_1_1hash_3_01dmlc_1_1optional_3_01T_01_4_01_4.html"> 254</a></span>&#160;<span class="keyword">struct </span>hash&lt;<a class="code" href="namespacedmlc.html">dmlc</a>::optional&lt;T&gt; &gt; {</div><div class="line"><a name="l00260"></a><span class="lineno"><a class="line" href="structstd_1_1hash_3_01dmlc_1_1optional_3_01T_01_4_01_4.html#a5c5faf408cca3c5aacd9a84e79e6420d"> 260</a></span>&#160; <span class="keywordtype">size_t</span> <a class="code" href="structstd_1_1hash_3_01dmlc_1_1optional_3_01T_01_4_01_4.html#a5c5faf408cca3c5aacd9a84e79e6420d">operator()</a>(<span class="keyword">const</span> <a class="code" href="classdmlc_1_1optional.html">dmlc::optional&lt;T&gt;</a>&amp; val)<span class="keyword"> const </span>{</div><div class="line"><a name="l00261"></a><span class="lineno"> 261</span>&#160; std::hash&lt;bool&gt; hash_bool;</div><div class="line"><a name="l00262"></a><span class="lineno"> 262</span>&#160; <span class="keywordtype">size_t</span> res = hash_bool(val.<a class="code" href="classdmlc_1_1optional.html#a0c135346d7c6425ce730493a89761c96">has_value</a>());</div><div class="line"><a name="l00263"></a><span class="lineno"> 263</span>&#160; <span class="keywordflow">if</span> (val.<a class="code" href="classdmlc_1_1optional.html#a0c135346d7c6425ce730493a89761c96">has_value</a>()) {</div><div class="line"><a name="l00264"></a><span class="lineno"> 264</span>&#160; res = <a class="code" href="namespacedmlc.html#a8620a9c7572cd3aab1ed3135b7a8e137">dmlc::HashCombine</a>(res, val.<a class="code" href="classdmlc_1_1optional.html#aaf22cb65a584841e054aa69e4acdd0be">value</a>());</div><div class="line"><a name="l00265"></a><span class="lineno"> 265</span>&#160; }</div><div class="line"><a name="l00266"></a><span class="lineno"> 266</span>&#160; <span class="keywordflow">return</span> res;</div><div class="line"><a name="l00267"></a><span class="lineno"> 267</span>&#160; }</div><div class="line"><a name="l00268"></a><span class="lineno"> 268</span>&#160;};</div><div class="line"><a name="l00269"></a><span class="lineno"> 269</span>&#160;} <span class="comment">// namespace std</span></div><div class="line"><a name="l00270"></a><span class="lineno"> 270</span>&#160;</div><div class="line"><a name="l00271"></a><span class="lineno"> 271</span>&#160;<span class="preprocessor">#endif // DMLC_OPTIONAL_H_</span></div><div class="ttc" id="namespacedmlc_html_ae0e0e4f86115e4c4e7f761de5c8a6797"><div class="ttname"><a href="namespacedmlc.html#ae0e0e4f86115e4c4e7f761de5c8a6797">dmlc::DMLC_DECLARE_TYPE_NAME</a></div><div class="ttdeci">DMLC_DECLARE_TYPE_NAME(optional&lt; int &gt;, &quot;int or None&quot;)</div><div class="ttdoc">description for optional int </div></div>
<div class="ttc" id="classdmlc_1_1optional_html"><div class="ttname"><a href="classdmlc_1_1optional.html">dmlc::optional</a></div><div class="ttdoc">c++17 compatible optional class. </div><div class="ttdef"><b>Definition:</b> optional.h:43</div></div>
<div class="ttc" id="classdmlc_1_1optional_html_aacd056f3191890afa191f8ad50ebf27f"><div class="ttname"><a href="classdmlc_1_1optional.html#aacd056f3191890afa191f8ad50ebf27f">dmlc::optional::~optional</a></div><div class="ttdeci">~optional()</div><div class="ttdoc">deconstructor </div><div class="ttdef"><b>Definition:</b> optional.h:70</div></div>
<div class="ttc" id="classdmlc_1_1optional_html_ad8d39fd99191c6f232063b60a1b7bb6f"><div class="ttname"><a href="classdmlc_1_1optional.html#ad8d39fd99191c6f232063b60a1b7bb6f">dmlc::optional::optional</a></div><div class="ttdeci">optional(const T &amp;value)</div><div class="ttdoc">construct an optional object with value </div><div class="ttdef"><b>Definition:</b> optional.h:48</div></div>
<div class="ttc" id="namespacestd_html"><div class="ttname"><a href="namespacestd.html">std</a></div><div class="ttdef"><b>Definition:</b> optional.h:251</div></div>
<div class="ttc" id="namespacedmlc_html_acc4b71c13985425358cb63cc45d49512"><div class="ttname"><a href="namespacedmlc.html#acc4b71c13985425358cb63cc45d49512">dmlc::operator&gt;&gt;</a></div><div class="ttdeci">std::istream &amp; operator&gt;&gt;(std::istream &amp;is, optional&lt; T &gt; &amp;t)</div><div class="ttdoc">parse a string object into optional&lt;T&gt; </div><div class="ttdef"><b>Definition:</b> optional.h:178</div></div>
<div class="ttc" id="classdmlc_1_1optional_html_a0a0f99e2ba48f2583f164c2286dacc58"><div class="ttname"><a href="classdmlc_1_1optional.html#a0a0f99e2ba48f2583f164c2286dacc58">dmlc::optional::optional</a></div><div class="ttdeci">optional(const optional&lt; T &gt; &amp;other)</div><div class="ttdoc">construct an optional object with another optional object </div><div class="ttdef"><b>Definition:</b> optional.h:58</div></div>
<div class="ttc" id="classdmlc_1_1optional_html_ab7b4fba71d2e988cd5dacb99a5da315e"><div class="ttname"><a href="classdmlc_1_1optional.html#ab7b4fba71d2e988cd5dacb99a5da315e">dmlc::optional::operator=</a></div><div class="ttdeci">optional&lt; T &gt; &amp; operator=(const T &amp;value)</div><div class="ttdoc">set this object to hold value </div><div class="ttdef"><b>Definition:</b> optional.h:84</div></div>
<div class="ttc" id="classdmlc_1_1optional_html_a5c857b9eaf4721c111e3753cc7685cc0"><div class="ttname"><a href="classdmlc_1_1optional.html#a5c857b9eaf4721c111e3753cc7685cc0">dmlc::optional::operator==</a></div><div class="ttdeci">bool operator==(const optional&lt; T &gt; &amp;other) const</div><div class="ttdoc">equal comparison </div><div class="ttdef"><b>Definition:</b> optional.h:112</div></div>
<div class="ttc" id="namespacedmlc_html_a8620a9c7572cd3aab1ed3135b7a8e137"><div class="ttname"><a href="namespacedmlc.html#a8620a9c7572cd3aab1ed3135b7a8e137">dmlc::HashCombine</a></div><div class="ttdeci">size_t HashCombine(size_t key, const T &amp;value)</div><div class="ttdoc">hash an object and combines the key with previous keys </div><div class="ttdef"><b>Definition:</b> common.h:37</div></div>
<div class="ttc" id="namespacedmlc_html_a52dcf01c9ba22be9b08e455194fb2ab3"><div class="ttname"><a href="namespacedmlc.html#a52dcf01c9ba22be9b08e455194fb2ab3">dmlc::isspace</a></div><div class="ttdeci">bool isspace(char c)</div><div class="ttdoc">Inline implementation of isspace(). Tests whether the given character is a whitespace letter...</div><div class="ttdef"><b>Definition:</b> strtonum.h:26</div></div>
<div class="ttc" id="classdmlc_1_1optional_html_ad2959fc0d19a5e4affbc9e1cd67e57ae"><div class="ttname"><a href="classdmlc_1_1optional.html#ad2959fc0d19a5e4affbc9e1cd67e57ae">dmlc::optional::operator=</a></div><div class="ttdeci">optional&lt; T &gt; &amp; operator=(nullopt_t)</div><div class="ttdoc">clear the value this object is holding. optional&lt;T&gt; x = nullopt; </div><div class="ttdef"><b>Definition:</b> optional.h:99</div></div>
<div class="ttc" id="namespacedmlc_html"><div class="ttname"><a href="namespacedmlc.html">dmlc</a></div><div class="ttdoc">namespace for dmlc </div><div class="ttdef"><b>Definition:</b> array_view.h:12</div></div>
<div class="ttc" id="classdmlc_1_1optional_html_aca79e391f4df7aaca345d05ae65a4d16"><div class="ttname"><a href="classdmlc_1_1optional.html#aca79e391f4df7aaca345d05ae65a4d16">dmlc::optional::swap</a></div><div class="ttdeci">void swap(optional&lt; T &gt; &amp;other)</div><div class="ttdoc">swap two optional </div><div class="ttdef"><b>Definition:</b> optional.h:76</div></div>
<div class="ttc" id="namespacedmlc_html_a7e0f62af45e67c3b6fa22080e756b379"><div class="ttname"><a href="namespacedmlc.html#a7e0f62af45e67c3b6fa22080e756b379">dmlc::nullopt</a></div><div class="ttdeci">constexpr const nullopt_t nullopt</div><div class="ttdef"><b>Definition:</b> optional.h:33</div></div>
<div class="ttc" id="classdmlc_1_1optional_html_aaf22cb65a584841e054aa69e4acdd0be"><div class="ttname"><a href="classdmlc_1_1optional.html#aaf22cb65a584841e054aa69e4acdd0be">dmlc::optional::value</a></div><div class="ttdeci">const T &amp; value() const</div><div class="ttdoc">return the holded value. throws std::logic_error if holding no value </div><div class="ttdef"><b>Definition:</b> optional.h:119</div></div>
<div class="ttc" id="classdmlc_1_1optional_html_a0a8ba8634870786f4c8520b82550f57f"><div class="ttname"><a href="classdmlc_1_1optional.html#a0a8ba8634870786f4c8520b82550f57f">dmlc::optional::operator*</a></div><div class="ttdeci">const T &amp; operator*() const</div><div class="ttdoc">const dereference operator </div><div class="ttdef"><b>Definition:</b> optional.h:108</div></div>
<div class="ttc" id="classdmlc_1_1optional_html_a535a725a80a78681d96feac82c3f5110"><div class="ttname"><a href="classdmlc_1_1optional.html#a535a725a80a78681d96feac82c3f5110">dmlc::optional::operator=</a></div><div class="ttdeci">optional&lt; T &gt; &amp; operator=(const optional&lt; T &gt; &amp;other)</div><div class="ttdoc">set this object to hold the same value with other </div><div class="ttdef"><b>Definition:</b> optional.h:92</div></div>
<div class="ttc" id="structstd_1_1hash_3_01dmlc_1_1optional_3_01T_01_4_01_4_html_a5c5faf408cca3c5aacd9a84e79e6420d"><div class="ttname"><a href="structstd_1_1hash_3_01dmlc_1_1optional_3_01T_01_4_01_4.html#a5c5faf408cca3c5aacd9a84e79e6420d">std::hash&lt; dmlc::optional&lt; T &gt; &gt;::operator()</a></div><div class="ttdeci">size_t operator()(const dmlc::optional&lt; T &gt; &amp;val) const</div><div class="ttdoc">returns hash of the optional value. </div><div class="ttdef"><b>Definition:</b> optional.h:260</div></div>
<div class="ttc" id="classdmlc_1_1optional_html_a0c135346d7c6425ce730493a89761c96"><div class="ttname"><a href="classdmlc_1_1optional.html#a0c135346d7c6425ce730493a89761c96">dmlc::optional::has_value</a></div><div class="ttdeci">bool has_value() const</div><div class="ttdoc">whether this object is holding a value (alternate form). </div><div class="ttdef"><b>Definition:</b> optional.h:128</div></div>
<div class="ttc" id="classdmlc_1_1optional_html_a5df5732afa850c13c880db0db96c2702"><div class="ttname"><a href="classdmlc_1_1optional.html#a5df5732afa850c13c880db0db96c2702">dmlc::optional::operator*</a></div><div class="ttdeci">T &amp; operator*()</div><div class="ttdoc">non-const dereference operator </div><div class="ttdef"><b>Definition:</b> optional.h:104</div></div>
<div class="ttc" id="structdmlc_1_1nullopt__t_html_a0d5231f7d348cbab57afe3f4b601b51d"><div class="ttname"><a href="structdmlc_1_1nullopt__t.html#a0d5231f7d348cbab57afe3f4b601b51d">dmlc::nullopt_t::nullopt_t</a></div><div class="ttdeci">constexpr nullopt_t(int a)</div><div class="ttdoc">dummy constructor </div><div class="ttdef"><b>Definition:</b> optional.h:28</div></div>
<div class="ttc" id="3rdparty_2dmlc-core_2include_2dmlc_2base_8h_html"><div class="ttname"><a href="3rdparty_2dmlc-core_2include_2dmlc_2base_8h.html">base.h</a></div></div>
<div class="ttc" id="common_8h_html"><div class="ttname"><a href="common_8h.html">common.h</a></div><div class="ttdoc">defines some common utility function. </div></div>
<div class="ttc" id="structdmlc_1_1nullopt__t_html"><div class="ttname"><a href="structdmlc_1_1nullopt__t.html">dmlc::nullopt_t</a></div><div class="ttdoc">dummy type for assign null to optional </div><div class="ttdef"><b>Definition:</b> optional.h:22</div></div>
<div class="ttc" id="classdmlc_1_1optional_html_a358bf8befa660e58c07856b06c2e2b41"><div class="ttname"><a href="classdmlc_1_1optional.html#a358bf8befa660e58c07856b06c2e2b41">dmlc::optional::optional</a></div><div class="ttdeci">optional()</div><div class="ttdoc">construct an optional object that contains no value </div><div class="ttdef"><b>Definition:</b> optional.h:46</div></div>
<div class="ttc" id="type__traits_8h_html"><div class="ttname"><a href="type__traits_8h.html">type_traits.h</a></div><div class="ttdoc">type traits information header </div></div>
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