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>
<p>Returns a reference to the first element in the container. For a JSON container <code>c</code>, the expression <code>c.front()</code> is equivalent to <code>*c.<aclass="el"href="classnlohmann_1_1basic__json_af4261341695729a8e657b94772f95516.html#af4261341695729a8e657b94772f95516"title="returns an iterator to the first element ">begin()</a></code>.</p>
<dlclass="section return"><dt>Returns</dt><dd>In case of a compound value (array or object), a reference to the first element is returned. In cast of number, string, or boolean values, a reference to the value is returned.</dd></dl>
<dlclass="section note"><dt>Note</dt><dd>Calling <code>front</code> on an empty container is undefined.</dd></dl>
<dlclass="exception"><dt>Exceptions</dt><dd>
<tableclass="exception">
<tr><tdclass="paramname">std::out_of_range</td><td>when called on null value.</td></tr>
</table>
</dd>
</dl>
<dlclass="section user"><dt>Example</dt><dd>The following code shows an example for <aclass="el"href="classnlohmann_1_1basic__json_a83cbbfbf5d3ecbad6de8ece0be6b36c4.html#a83cbbfbf5d3ecbad6de8ece0be6b36c4">front</a>. <divclass="fragment"><divclass="line"><aname="l00001"></a><spanclass="lineno"> 1</span> <spanclass="preprocessor">#include <json.hpp></span></div>
<divclass="ttc"id="classnlohmann_1_1basic__json_a83cbbfbf5d3ecbad6de8ece0be6b36c4_html_a83cbbfbf5d3ecbad6de8ece0be6b36c4"><divclass="ttname"><ahref="classnlohmann_1_1basic__json_a83cbbfbf5d3ecbad6de8ece0be6b36c4.html#a83cbbfbf5d3ecbad6de8ece0be6b36c4">nlohmann::basic_json::front</a></div><divclass="ttdeci">reference front()</div><divclass="ttdoc">access the first element </div><divclass="ttdef"><b>Definition:</b> json.hpp:1753</div></div>
<divclass="ttc"id="classnlohmann_1_1basic__json_html"><divclass="ttname"><ahref="classnlohmann_1_1basic__json.html">nlohmann::basic_json</a></div><divclass="ttdoc">a class to store JSON values </div><divclass="ttdef"><b>Definition:</b> json.hpp:113</div></div>
<divclass="ttc"id="classnlohmann_1_1basic__json_a231b02148577b69a154b2ce2c87a5522_html_a231b02148577b69a154b2ce2c87a5522aa8cfde6331bd59eb2ac96f8911c4b666"><divclass="ttname"><ahref="classnlohmann_1_1basic__json_a231b02148577b69a154b2ce2c87a5522.html#a231b02148577b69a154b2ce2c87a5522aa8cfde6331bd59eb2ac96f8911c4b666">nlohmann::basic_json::value_t::object</a></div><divclass="ttdoc">object (unordered set of name/value pairs) </div></div>
<divclass="ttc"id="namespacenlohmann_html"><divclass="ttname"><ahref="namespacenlohmann.html">nlohmann</a></div><divclass="ttdoc">namespace for Niels Lohmann </div><divclass="ttdef"><b>Definition:</b> json.hpp:49</div></div>
<divclass="ttc"id="classnlohmann_1_1basic__json_a231b02148577b69a154b2ce2c87a5522_html_a231b02148577b69a154b2ce2c87a5522af1f713c9e000f5d3f280adbd124df4f5"><divclass="ttname"><ahref="classnlohmann_1_1basic__json_a231b02148577b69a154b2ce2c87a5522.html#a231b02148577b69a154b2ce2c87a5522af1f713c9e000f5d3f280adbd124df4f5">nlohmann::basic_json::value_t::array</a></div><divclass="ttdoc">array (ordered collection of values) </div></div>
</div><!-- fragment --> Output: <preclass="fragment">true
17
23.42
1
1
"Hello, world"
</pre> The example code above can be translated with<preclass="fragment">g++ -std=c++11 -Isrc doc/examples/front.cpp -o front </pre>. </dd></dl>
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