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template<template< typename U, typename V, typename...Args > class ObjectType = std::map, template< typename U, typename...Args > class ArrayType = std::vector, class StringType = std::string, class BooleanType = bool, class NumberIntegerType = int64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator> </div>
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<td class="memname"><a class="el" href="classnlohmann_1_1basic__json.html">nlohmann::basic_json</a>::<a class="el" href="classnlohmann_1_1basic__json.html">basic_json</a> </td>
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<td>(</td>
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<td class="paramtype"><a class="el" href="classnlohmann_1_1basic__json_aa23ac5808b9aa1a08d18e3ebea25c7ce.html#aa23ac5808b9aa1a08d18e3ebea25c7ce">list_init_t</a> </td>
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<td class="paramname"><em>init</em>, </td>
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</tr>
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<tr>
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<td class="paramkey"></td>
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<td></td>
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<td class="paramtype">bool </td>
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<td class="paramname"><em>type_deduction</em> = <code>true</code>, </td>
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</tr>
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<tr>
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<td class="paramkey"></td>
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<td></td>
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<td class="paramtype"><a class="el" href="classnlohmann_1_1basic__json_a231b02148577b69a154b2ce2c87a5522.html#a231b02148577b69a154b2ce2c87a5522">value_t</a> </td>
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<td class="paramname"><em>manual_type</em> = <code><a class="el" href="classnlohmann_1_1basic__json_a231b02148577b69a154b2ce2c87a5522.html#a231b02148577b69a154b2ce2c87a5522af1f713c9e000f5d3f280adbd124df4f5">value_t::array</a></code> </td>
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<td>)</td>
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</div><div class="memdoc">
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<p>Creates a JSON value of type array or object from the passed initializer list <em>init</em>. In case <em>type_deduction</em> is <code>true</code> (default), the type of the JSON value to be created is deducted from the initializer list <em>init</em> according to the following rules:</p>
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<ol type="1">
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<li>If the list is empty, an empty JSON object value <code>{}</code> is created.</li>
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<li>If the list consists of pairs whose first element is a string, a JSON object value is created where the first elements of the pairs are treated as keys and the second elements are as values.</li>
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<li>In all other cases, an array is created.</li>
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</ol>
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<p>The rules aim to create the best fit between a C++ initializer list and JSON values. The ratioinale is as follows:</p>
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<ol type="1">
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<li>The empty initializer list is written as <code>{}</code> which is exactly an empty JSON object.</li>
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<li>C++ has now way of describing mapped types other than to list a list of pairs. As JSON requires that keys must be of type string, rule 2 is the weakest constraint one can pose on initializer lists to interpret them as an object.</li>
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<li>In all other cases, the initializer list could not be interpreted as JSON object type, so interpreting it as JSON array type is safe.</li>
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</ol>
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<p>With the rules described above, the following JSON values cannot be expressed by an initializer list:</p>
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<ul>
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<li>the empty array (<code>[]</code>): use <a class="el" href="classnlohmann_1_1basic__json_a53590b99e380c464a83a0a5edf6da9ab.html#a53590b99e380c464a83a0a5edf6da9ab">array(list_init_t)</a> with an empty initializer list in this case</li>
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<li>arrays whose elements satisfy rule 2: use <a class="el" href="classnlohmann_1_1basic__json_a53590b99e380c464a83a0a5edf6da9ab.html#a53590b99e380c464a83a0a5edf6da9ab">array(list_init_t)</a> with the same initializer list in this case</li>
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</ul>
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<dl class="section note"><dt>Note</dt><dd>When used without parentheses around an empty initializer list, <a class="el" href="classnlohmann_1_1basic__json_a5a2d4dbcdbc8ea065b87daf52cd786b9.html#a5a2d4dbcdbc8ea065b87daf52cd786b9">basic_json()</a> is called instead of this function, yielding the JSON null value.</dd></dl>
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<dl class="params"><dt>Parameters</dt><dd>
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<table class="params">
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<tr><td class="paramdir">[in]</td><td class="paramname">init</td><td>initializer list with JSON values</td></tr>
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<tr><td class="paramdir">[in]</td><td class="paramname">type_deduction</td><td>internal parameter; when set to <code>true</code>, the type of the JSON value is deducted from the initializer list <em>init</em>; when set to <code>false</code>, the type provided via <em>manual_type</em> is forced. This mode is used by the functions <a class="el" href="classnlohmann_1_1basic__json_a53590b99e380c464a83a0a5edf6da9ab.html#a53590b99e380c464a83a0a5edf6da9ab">array(list_init_t)</a> and <a class="el" href="classnlohmann_1_1basic__json_afb9664e6f30038e691f2e864e7f6a740.html#afb9664e6f30038e691f2e864e7f6a740">object(list_init_t)</a>.</td></tr>
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<tr><td class="paramdir">[in]</td><td class="paramname">manual_type</td><td>internal parameter; when <em>type_deduction</em> is set to <code>false</code>, the created JSON value will use the provided type (only <a class="el" href="classnlohmann_1_1basic__json_a231b02148577b69a154b2ce2c87a5522.html#a231b02148577b69a154b2ce2c87a5522af1f713c9e000f5d3f280adbd124df4f5">value_t::array</a> and <a class="el" href="classnlohmann_1_1basic__json_a231b02148577b69a154b2ce2c87a5522.html#a231b02148577b69a154b2ce2c87a5522aa8cfde6331bd59eb2ac96f8911c4b666">value_t::object</a> are valid); when <em>type_deduction</em> is set to <code>true</code>, this parameter has no effect</td></tr>
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</table>
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</dd>
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</dl>
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<dl class="exception"><dt>Exceptions</dt><dd>
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<table class="exception">
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<tr><td class="paramname">std::domain_error</td><td>if <em>type_deduction</em> is <code>false</code>, <em>manual_type</em> is <code><a class="el" href="classnlohmann_1_1basic__json_a231b02148577b69a154b2ce2c87a5522.html#a231b02148577b69a154b2ce2c87a5522aa8cfde6331bd59eb2ac96f8911c4b666" title="object (unordered set of name/value pairs) ">value_t::object</a></code>, but <em>init</em> contains an element which is not a pair whose first element is a string</td></tr>
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</table>
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</dd>
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</dl>
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<dl class="section user"><dt>Complexity</dt><dd>Linear in the size of the initializer list <em>init</em>.</dd></dl>
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<dl class="section user"><dt>Example</dt><dd>The example below shows how JSON values are created from initializer lists <div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> <span class="preprocessor">#include <json.hpp></span></div>
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<div class="line"><a name="l00002"></a><span class="lineno"> 2</span> </div>
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<div class="line"><a name="l00003"></a><span class="lineno"> 3</span> <span class="keyword">using namespace </span><a class="code" href="namespacenlohmann.html">nlohmann</a>;</div>
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<div class="line"><a name="l00004"></a><span class="lineno"> 4</span> </div>
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<div class="line"><a name="l00005"></a><span class="lineno"> 5</span> <span class="keywordtype">int</span> main()</div>
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<div class="line"><a name="l00006"></a><span class="lineno"> 6</span> {</div>
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<div class="line"><a name="l00007"></a><span class="lineno"> 7</span>  <span class="comment">// create JSON values</span></div>
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<div class="line"><a name="l00008"></a><span class="lineno"> 8</span>  <a class="code" href="classnlohmann_1_1basic__json.html">json</a> j_empty_init_list = <a class="code" href="namespacenlohmann_a2bfd99e845a2e5cd90aeaf1b1431f474.html#a2bfd99e845a2e5cd90aeaf1b1431f474">json</a>({});</div>
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<div class="line"><a name="l00009"></a><span class="lineno"> 9</span>  <a class="code" href="classnlohmann_1_1basic__json.html">json</a> j_object = { {<span class="stringliteral">"one"</span>, 1}, {<span class="stringliteral">"two"</span>, 2} };</div>
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<div class="line"><a name="l00010"></a><span class="lineno"> 10</span>  <a class="code" href="classnlohmann_1_1basic__json.html">json</a> j_array = {1, 2, 3, 4};</div>
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<div class="line"><a name="l00011"></a><span class="lineno"> 11</span>  <a class="code" href="classnlohmann_1_1basic__json.html">json</a> j_nested_object = { {<span class="stringliteral">"one"</span>, {1}}, {<span class="stringliteral">"two"</span>, {1, 2}} };</div>
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<div class="line"><a name="l00012"></a><span class="lineno"> 12</span>  <a class="code" href="classnlohmann_1_1basic__json.html">json</a> j_nested_array = { {{1}, <span class="stringliteral">"one"</span>}, {{1, 2}, <span class="stringliteral">"two"</span>} };</div>
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<div class="line"><a name="l00013"></a><span class="lineno"> 13</span> </div>
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<div class="line"><a name="l00014"></a><span class="lineno"> 14</span>  <span class="comment">// serialize the JSON value</span></div>
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<div class="line"><a name="l00015"></a><span class="lineno"> 15</span>  std::cout << j_empty_init_list << <span class="charliteral">'\n'</span>;</div>
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<div class="line"><a name="l00016"></a><span class="lineno"> 16</span>  std::cout << j_object << <span class="charliteral">'\n'</span>;</div>
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<div class="line"><a name="l00017"></a><span class="lineno"> 17</span>  std::cout << j_array << <span class="charliteral">'\n'</span>;</div>
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<div class="line"><a name="l00018"></a><span class="lineno"> 18</span>  std::cout << j_nested_object << <span class="charliteral">'\n'</span>;</div>
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<div class="line"><a name="l00019"></a><span class="lineno"> 19</span>  std::cout << j_nested_array << <span class="charliteral">'\n'</span>;</div>
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<div class="line"><a name="l00020"></a><span class="lineno"> 20</span> }</div>
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<div class="ttc" id="namespacenlohmann_a2bfd99e845a2e5cd90aeaf1b1431f474_html_a2bfd99e845a2e5cd90aeaf1b1431f474"><div class="ttname"><a href="namespacenlohmann_a2bfd99e845a2e5cd90aeaf1b1431f474.html#a2bfd99e845a2e5cd90aeaf1b1431f474">nlohmann::json</a></div><div class="ttdeci">basic_json<> json</div><div class="ttdoc">default JSON class </div><div class="ttdef"><b>Definition:</b> json.hpp:5979</div></div>
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<div class="ttc" id="classnlohmann_1_1basic__json_html"><div class="ttname"><a href="classnlohmann_1_1basic__json.html">nlohmann::basic_json</a></div><div class="ttdoc">a class to store JSON values </div><div class="ttdef"><b>Definition:</b> json.hpp:121</div></div>
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<div class="ttc" id="namespacenlohmann_html"><div class="ttname"><a href="namespacenlohmann.html">nlohmann</a></div><div class="ttdoc">namespace for Niels Lohmann </div><div class="ttdef"><b>Definition:</b> json.hpp:56</div></div>
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</div><!-- fragment --> Output: <pre class="fragment">{}
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{"one":1,"two":2}
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[1,2,3,4]
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{"one":[1],"two":[1,2]}
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[[[1],"one"],[[1,2],"two"]]
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</pre> The example code above can be translated with<pre class="fragment">g++ -std=c++11 -Isrc doc/examples/basic_json__list_init_t.cpp -o basic_json__list_init_t </pre>.</dd></dl>
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<dl class="section see"><dt>See also</dt><dd><a class="el" href="classnlohmann_1_1basic__json.html" title="a class to store JSON values ">basic_json</a> <a class="el" href="classnlohmann_1_1basic__json_a53590b99e380c464a83a0a5edf6da9ab.html#a53590b99e380c464a83a0a5edf6da9ab" title="explicitly create an array from an initializer list ">array(list_init_t)</a> - create a JSON <a class="el" href="classnlohmann_1_1basic__json_a53590b99e380c464a83a0a5edf6da9ab.html#a53590b99e380c464a83a0a5edf6da9ab" title="explicitly create an array from an initializer list ">array</a> value from an initializer list </dd>
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<dd>
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<a class="el" href="classnlohmann_1_1basic__json.html" title="a class to store JSON values ">basic_json</a> <a class="el" href="classnlohmann_1_1basic__json_afb9664e6f30038e691f2e864e7f6a740.html#afb9664e6f30038e691f2e864e7f6a740" title="explicitly create an object from an initializer list ">object(list_init_t)</a> - create a JSON <a class="el" href="classnlohmann_1_1basic__json_afb9664e6f30038e691f2e864e7f6a740.html#afb9664e6f30038e691f2e864e7f6a740" title="explicitly create an object from an initializer list ">object</a> value from an initializer list </dd></dl>
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<li class="footer">Generated on Mon Jun 22 2015 23:22:00 for JSON for Modern C++ by
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<img class="footer" src="doxygen.png" alt="doxygen"/></a> 1.8.9.1 </li>
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