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<header data-kunai-mdinfo="{&#34;meta&#34;: {&#34;header&#34;: [&#34;charconv&#34;], &#34;id-type&#34;: [&#34;function&#34;], &#34;namespace&#34;: [&#34;std&#34;], &#34;cpp&#34;: [&#34;cpp17&#34;]}, &#34;sources&#34;: [{&#34;id&#34;: &#34;e3e678615764dd8d9c57df6715b41fcffa9f223d&#34;, &#34;source&#34;: &#34;#include &lt;iostream&gt;\n#include &lt;charconv&gt;\n#include &lt;string_view&gt;\n\nint main()\n{\n  char out[50]{};\n  auto begin = std::begin(out);\n  auto end = std::end(out);\n\n  //(1) 10\u9032\u6570\u6587\u5b57\u5217\u3078\u5909\u63db\n  if (auto [ptr, ec] = std::to_chars(begin, end, 10); ec == std::errc{}) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n  //(1) 2\u9032\u6570\u6587\u5b57\u5217\u3078\u5909\u63db\n  if (auto [ptr, ec] = std::to_chars(begin, end, 65535, 2); ec == std::errc{}) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n  //(1) 36\u9032\u6570\u6587\u5b57\u5217\u3078\u5909\u63db\n  if (auto [ptr, ec] = std::to_chars(begin, end, 35, 36); ec == std::errc{}) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n\n  //\u30ea\u30a6\u30f4\u30a3\u30eb\u6570\n  constexpr double l = 0.11000100000000000000000100000000000;\n\n  //(3) \u7cbe\u5ea6\u30fb\u30d5\u30a9\u30fc\u30de\u30c3\u30c8\u6307\u5b9a\u306a\u3057\u306e\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u5909\u63db\n  if (auto [ptr, ec] = std::to_chars(begin, end, l); ec == std::errc{}) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n\n  //(7) \u7cbe\u5ea6\u6307\u5b9a\u306a\u3057\u306e\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u5909\u63db\u3001\u6307\u6570\u8868\u8a18\n  if (auto [ptr, ec] = std::to_chars(begin, end, l, std::chars_format::scientific); ec == std::errc{}) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n  //(7) \u7cbe\u5ea6\u6307\u5b9a\u306a\u3057\u306e\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u5909\u63db\u3001\u56fa\u5b9a\u5c0f\u6570\u8868\u8a18\n  if (auto [ptr, ec] = std::to_chars(begin, end, l, std::chars_format::fixed); ec == std::errc{}) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n  //(7) \u7cbe\u5ea6\u6307\u5b9a\u306a\u3057\u306e\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u5909\u63db\u300116\u9032\u6307\u6570\u8868\u8a18\n  if (auto [ptr, ec] = std::to_chars(begin, end, l, std::chars_format::hex); ec == std::errc{}) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n\n  //(11) \u7cbe\u5ea6\u6307\u5b9a\u3042\u308a\u306e\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u5909\u63db\u3001\u6307\u6570\u8868\u8a18\n  if (auto [ptr, ec] = std::to_chars(begin, end, l, std::chars_format::scientific, 16); ec == std::errc{}) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n  //(11) \u7cbe\u5ea6\u6307\u5b9a\u3042\u308a\u306e\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u5909\u63db\u3001\u56fa\u5b9a\u5c0f\u6570\u8868\u8a18\n  if (auto [ptr, ec] = std::to_chars(begin, end, l, std::chars_format::fixed, 16); ec == std::errc{}) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n  //(11) \u7cbe\u5ea6\u6307\u5b9a\u3042\u308a\u306e\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u5909\u63db\u300116\u9032\u6307\u6570\u8868\u8a18\n  if (auto [ptr, ec] = std::to_chars(begin, end, l, std::chars_format::hex, 16); ec == std::errc{}) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n}\n&#34;}, {&#34;id&#34;: &#34;648e21f1840110bd3727f4d4a34d11fa6e6cea89&#34;, &#34;source&#34;: &#34;#include &lt;iostream&gt;\n#include &lt;charconv&gt;\n\nint main()\n{\n  char out[50]{};\n  auto begin = std::begin(out);\n  auto end = std::end(out);\n\n  //(1) 10\u9032\u6570\u6587\u5b57\u5217\u3078\u5909\u63db\n  if (auto [ptr, ec] = std::to_chars(begin, end, 10)) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n  //(1) 2\u9032\u6570\u6587\u5b57\u5217\u3078\u5909\u63db\n  if (auto [ptr, ec] = std::to_chars(begin, end, 65535, 2)) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n  //(1) 36\u9032\u6570\u6587\u5b57\u5217\u3078\u5909\u63db\n  if (auto [ptr, ec] = std::to_chars(begin, end, 35, 36)) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n\n  //\u30ea\u30a6\u30f4\u30a3\u30eb\u6570\n  constexpr double l = 0.11000100000000000000000100000000000;\n\n  //(3) \u7cbe\u5ea6\u30fb\u30d5\u30a9\u30fc\u30de\u30c3\u30c8\u6307\u5b9a\u306a\u3057\u306e\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u5909\u63db\n  if (auto [ptr, ec] = std::to_chars(begin, end, l)) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n\n  //(7) \u7cbe\u5ea6\u6307\u5b9a\u306a\u3057\u306e\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u5909\u63db\u3001\u6307\u6570\u8868\u8a18\n  if (auto [ptr, ec] = std::to_chars(begin, end, l, std::chars_format::scientific)) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n  //(7) \u7cbe\u5ea6\u6307\u5b9a\u306a\u3057\u306e\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u5909\u63db\u3001\u56fa\u5b9a\u5c0f\u6570\u8868\u8a18\n  if (auto [ptr, ec] = std::to_chars(begin, end, l, std::chars_format::fixed)) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n  //(7) \u7cbe\u5ea6\u6307\u5b9a\u306a\u3057\u306e\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u5909\u63db\u300116\u9032\u6307\u6570\u8868\u8a18\n  if (auto [ptr, ec] = std::to_chars(begin, end, l, std::chars_format::hex)) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n\n  //(11) \u7cbe\u5ea6\u6307\u5b9a\u3042\u308a\u306e\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u5909\u63db\u3001\u6307\u6570\u8868\u8a18\n  if (auto [ptr, ec] = std::to_chars(begin, end, l, std::chars_format::scientific, 16)) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n  //(11) \u7cbe\u5ea6\u6307\u5b9a\u3042\u308a\u306e\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u5909\u63db\u3001\u56fa\u5b9a\u5c0f\u6570\u8868\u8a18\n  if (auto [ptr, ec] = std::to_chars(begin, end, l, std::chars_format::fixed, 16)) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n  //(11) \u7cbe\u5ea6\u6307\u5b9a\u3042\u308a\u306e\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u5909\u63db\u300116\u9032\u6307\u6570\u8868\u8a18\n  if (auto [ptr, ec] = std::to_chars(begin, end, l, std::chars_format::hex, 16)) {\n    std::cout &lt;&lt; std::string_view(begin, ptr - begin) &lt;&lt; std::endl;\n  }\n  else {\n    std::cout &lt;&lt; \&#34;conversion failed.\&#34; &lt;&lt; std::endl;\n  }\n}\n&#34;}], &#34;page_id&#34;: [&#34;reference&#34;, &#34;charconv&#34;, &#34;to_chars&#34;]}">
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  <div class="identifier-type">function</div><div class="header">&lt;charconv&gt;</div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="token">to_chars</span><span class="cpp cpp17" title="C++17で追加">(C++17)</span></h1>
<div itemprop="articleBody"><p><div class="codehilite"><pre><span></span><code><span class="k">namespace</span><span class="w"> </span><span class="nn">std</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="c1">//整数型用</span>
<span class="w">  </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="n"><i>see below</i></span><span class="w"> </span><span class="n">value</span><span class="p">,</span>
<span class="w">             </span><span class="kt">int</span><span class="w"> </span><span class="n">base</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">10</span><span class="p">);</span><span class="w">        </span><span class="c1">// (1) C++17</span>
<span class="w">  </span><span class="k">constexpr</span><span class="w"> </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="n"><i>integer-type</i></span><span class="w"> </span><span class="n">value</span><span class="p">,</span>
<span class="w">             </span><span class="kt">int</span><span class="w"> </span><span class="n">base</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">10</span><span class="p">);</span><span class="w">        </span><span class="c1">// (1) C++23</span>
<span class="w">  </span><span class="c1">//boolの変換は禁止</span>
<span class="w">  </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="kt">bool</span><span class="w"> </span><span class="n">value</span><span class="p">,</span>
<span class="w">             </span><span class="kt">int</span><span class="w"> </span><span class="n">base</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">10</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">delete</span><span class="p">;</span><span class="w"> </span><span class="c1">// C++20</span>
<span class="w">  </span><span class="c1">//精度、フォーマット指定なし</span>
<span class="w">  </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="kt">float</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">               </span><span class="c1">// (2) C++17からC++20まで</span>
<span class="w">  </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="kt">double</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">              </span><span class="c1">// (3) C++17からC++20まで</span>
<span class="w">  </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="kt">long</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">         </span><span class="c1">// (4) C++17からC++20まで</span>
<span class="w">  </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="n"><i>floating-point-type</i></span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w"> </span><span class="c1">// (5) C++23</span>
<span class="w">  </span><span class="c1">//精度指定なし</span>
<span class="w">  </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="kt">float</span><span class="w"> </span><span class="n">value</span><span class="p">,</span>
<span class="w">             </span><span class="n">chars_format</span><span class="w"> </span><span class="n">fmt</span><span class="p">);</span><span class="w">          </span><span class="c1">// (6) C++17からC++20まで</span>
<span class="w">  </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="kt">double</span><span class="w"> </span><span class="n">value</span><span class="p">,</span>
<span class="w">             </span><span class="n">chars_format</span><span class="w"> </span><span class="n">fmt</span><span class="p">);</span><span class="w">          </span><span class="c1">// (7) C++17からC++20まで</span>
<span class="w">  </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="kt">long</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">value</span><span class="p">,</span>
<span class="w">             </span><span class="n">chars_format</span><span class="w"> </span><span class="n">fmt</span><span class="p">);</span><span class="w">          </span><span class="c1">// (8) C++17からC++20まで</span>
<span class="w">  </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="n"><i>floating-point-type</i></span><span class="w"> </span><span class="n">value</span><span class="p">,</span>
<span class="w">             </span><span class="n">chars_format</span><span class="w"> </span><span class="n">fmt</span><span class="p">);</span><span class="w">          </span><span class="c1">// (9) C++23</span>
<span class="w">  </span><span class="c1">//精度とフォーマットを指定</span>
<span class="w">  </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="kt">float</span><span class="w"> </span><span class="n">value</span><span class="p">,</span>
<span class="w">             </span><span class="n">chars_format</span><span class="w"> </span><span class="n">fmt</span><span class="p">,</span>
<span class="w">             </span><span class="kt">int</span><span class="w"> </span><span class="n">precision</span><span class="p">);</span><span class="w">             </span><span class="c1">// (10) C++17からC++20まで</span>
<span class="w">  </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="kt">double</span><span class="w"> </span><span class="n">value</span><span class="p">,</span>
<span class="w">             </span><span class="n">chars_format</span><span class="w"> </span><span class="n">fmt</span><span class="p">,</span>
<span class="w">             </span><span class="kt">int</span><span class="w"> </span><span class="n">precision</span><span class="p">);</span><span class="w">             </span><span class="c1">// (11) C++17からC++20まで</span>
<span class="w">  </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="kt">long</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">value</span><span class="p">,</span>
<span class="w">             </span><span class="n">chars_format</span><span class="w"> </span><span class="n">fmt</span><span class="p">,</span>
<span class="w">             </span><span class="kt">int</span><span class="w"> </span><span class="n">precision</span><span class="p">);</span><span class="w">             </span><span class="c1">// (12) C++17からC++20まで</span>
<span class="w">  </span><span class="n"><a href="to_chars_result.html">to_chars_result</a></span>
<span class="w">    </span><span class="nf">to_chars</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w">             </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w">             </span><span class="n"><i>floating-point-type</i></span><span class="w"> </span><span class="n">value</span><span class="p">,</span>
<span class="w">             </span><span class="n">chars_format</span><span class="w"> </span><span class="n">fmt</span><span class="p">,</span>
<span class="w">             </span><span class="kt">int</span><span class="w"> </span><span class="n">precision</span><span class="p">);</span><span class="w">             </span><span class="c1">// (13) C++23</span>
<span class="p">}</span>
</code></pre></div>
<h2>概要</h2>
<p>与えられた数値（<code>value</code>）を文字列へ変換し、<code>[first, last)</code>内へ出力する。<br />
変換に際し、メモリ確保を行わず<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を投げることもない。</p>
<p>C++標準はこれら関数の実装の詳細について何も規定しない。これは、各実装において可能な最も高速なアルゴリズムが選択されることを意図しての事である。</p>
<li>(1) : 整数型に対する<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a></li>
<li>(2) : <code>float</code>に対する<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a> (精度・フォーマット指定なし)</li>
<li>(3) : <code>double</code>に対する<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a> (精度・フォーマット指定なし)</li>
<li>(4) : <code>long double</code>に対する<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a> (精度・フォーマット指定なし)</li>
<li>(5) : 浮動小数点数型に対する<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a> (精度・フォーマット指定なし)</li>
<li>(6) : <code>float</code>に対する<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a> (精度指定なし)</li>
<li>(7) : <code>double</code>に対する<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a> (精度指定なし)</li>
<li>(8) : <code>long double</code>に対する<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a> (精度指定なし)</li>
<li>(9) : 浮動小数点数型に対する<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a> (精度指定なし)</li>
<li>(10) : <code>float</code>に対する<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a> (精度・フォーマット指定)</li>
<li>(11) : <code>double</code>に対する<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a> (精度・フォーマット指定)</li>
<li>(12) : <code>long double</code>に対する<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a> (精度・フォーマット指定)</li>
<li>(13) : 浮動小数点数型に対する<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a> (精度・フォーマット指定)</li>
<h2>要件</h2>
<li>全て : 出力<a class="cpprefjp-defined-word" data-desc="2つのイテレータで表現される半開区間を表す。C++20からイテレータと番兵で異なる型であっても指定可能になる">イテレータ範囲</a><code>[first, last)</code>は有効な範囲であること（charのオブジェクトが構築済みであり、連続していること）。</li>
<li>(1) : <code>base</code>は2～36までの値であること。</li>
<li>(6)-(13)  : <code>fmt</code>は<code><a href="chars_format.html">chars_format</a></code>の列挙値のうちの一つであること。</li>
<h2>引数</h2>
<li><code>first</code> -- 変換結果の文字列を出力する範囲の先頭ポインタ。</li>
<li><code>last</code> -- 変換結果の文字列を出力する範囲の終端ポインタ。</li>
<li><code>value</code> -- 文字列へ変換する値。</li>
<li><code>base</code> -- 整数の出力基数（n進数のn）指定、2進数から36進数まで。</li>
<li><code>fmt</code> -- 浮動小数点数の出力フォーマット指定、<code><a href="chars_format.html">chars_format</a></code>のいずれか。</li>
<li><code>precision</code> -- 浮動小数点数の出力精度（小数点以下の桁数）指定、<code>printf</code>において<code>%.nf, %.ne</code>などとしたときの<code>n</code>にあたる。</li>
<h2>効果</h2>
<p>全て : <code>value</code>の値を文字列へ変換し、結果文字列を<code>[first, last)</code>に書き込む。<br />
    出力文字列が<code>[first, last)</code>に収まらない場合は失敗する。</p>
<p>(1) : <code>base</code>の値をnとすると、整数値をn進数の文字列へ変換する（ <code>value</code>が負なら<code>-</code>が先頭に付く）。<br />
    10 &lt; nの場合、10～35の値はアルファベットの小文字a～zがあてられる。<br />
    桁数を合わせるために左側を0でパディングすること（0埋め）は行われない。</p>
<p>(2), (3), (4), (5) : Cロケールで<code>printf</code>によって行われたかのように浮動小数点数を文字列へ変換する。<br />
    フォーマット指定子は<code>%f,%e</code>どちらかを出力文字列が最も短くなるように（両者が同じなら<code>%f</code>が優先）選択する。</p>
<p>(6), (7), (8), (9) : <code>fmt</code>によって指定されたフォーマット指定子を用いて、Cロケールで<code>printf</code>によって行われたかのように浮動小数点数を文字列へ変換する。<br />
    出力文字列が最も短くなるように変換される。<br />
<code>chars_format::general</code>が指定された場合は(2), (3), (4), (5)と同等。</p>
<p>(10), (11), (12), (13) : <code>fmt</code>と<code>precision</code>によって指定されたフォーマット指定子と精度を用いて、Cロケールで<code>printf</code>によって行われたかのように浮動小数点数を文字列へ変換する。<br />
    精度は、<code>chars_format::fixed</code>では小数点以下の正確な桁数、<code>chars_format::scientific</code>と<code>chars_format::hex</code>では最小の桁数を表す。<br />
<code>chars_format::general</code>が指定された場合は次のようになる。</p>
<li>指数表記したときの指数を<code>X</code>、<code>precision</code>と1の大きいほうを<code>P</code>とする。</li>
<li><code>P &gt; X ≥ −4</code> のとき、精度 <code>P - 1 - X</code> で固定小数形式を使用する。</li>
<li>それ以外の場合は、精度 <code>P - 1</code> で指数形式を使用する。</li>
<p>出力文字列が最も短くなるようにとは、小数点の前に少なくとも1桁あり、対応する<code><a href="from_chars.html">from_chars</a></code>関数によって値を正確に復元できるような最小の文字数、になることである。<br />
そのような文字列表現が複数ある場合、<code>value</code>の値との差が最も小さくなる物が選ばれ、それも複数あるときは<code><a href="../limits/float_round_style.html">std::round_to_nearest</a></code>に従った丸めによって一つを選択する。</p>
<p>なお、<code><a href="from_chars.html">from_chars</a></code>関数によって値を正確に復元できるのは両関数が同じ処理系で提供されているときにのみ保証される。</p>
<p>全ての<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a>において、変換に失敗した場合の<code>[first, last)</code>の状態は<a class="cpprefjp-defined-word" data-desc="未規定の動作。事前の断りなく処理系によって異なる動作をする" href="../../implementation-compliance.html#dfn-unspecified-behavior">未規定</a>。</p>
<h2><a class="cpprefjp-defined-word" data-desc="関数呼び出し式の評価結果となるオブジェクト・値">戻り値</a></h2>
<p><code><a href="to_chars_result.html">to_chars_result</a></code>の値。</p>
<li>成功した場合<ul>
<li><code>ptr</code> : 書き込まれた最後の文字の次の位置を指す（一般的な<a class="cpprefjp-defined-word" data-desc="2つのイテレータで表現される半開区間を表す。C++20からイテレータと番兵で異なる型であっても指定可能になる">イテレータ範囲</a>におけるendに相当）。</li>
<li><code>ec</code> : <code>ec == errc{}</code></li>
<li>失敗した場合<ul>
<li><code>ptr</code> : <code>ptr == last</code></li>
<li><code>ec</code> : <code>ec == <a href="../system_error/errc.html">errc::value_too_large</a></code></li>
<p>どちらの場合も<code>*ptr == '\0'</code>や<code>*(--ptr) == '\0'</code>は保証されない。すなわち、変換後文字列はnull終端されない。</p>
<h2><a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a></h2>
<p>投げない。</p>
<h2>備考</h2>
<li>MSVCでは浮動小数点数→10進文字列変換の実装に<a href="https://github.com/ulfjack/ryu" target="_blank">Ryu</a>というアルゴリズムを利用している。</li>
<li>(1) : 実装によって全ての整数型（符号付、無し）および<code>char</code>の<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a>が提供される</li>
<li>(5), (9), (13) : 浮動小数点数型は<a class="cpprefjp-defined-word" data-desc="&lt;stdfloat&gt;で定義される内部表現の規定された浮動小数点数型" href="../stdfloat.html">拡張浮動小数点数型</a>を含む</li>
<h3>基本の使用例 (C++17)</h3>
<p><div class="yata" id="e3e678615764dd8d9c57df6715b41fcffa9f223d"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html">&lt;iostream&gt;</a></span>
<span class="cp">#include <a href="../charconv.html">&lt;charconv&gt;</a></span>
<span class="cp">#include <a href="../string_view.html">&lt;string_view&gt;</a></span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="w">  </span><span class="kt">char</span><span class="w"> </span><span class="n">out</span><span class="p">[</span><span class="mi">50</span><span class="p">]{};</span>
<span class="w">  </span><span class="k">auto</span><span class="w"> </span><span class="n">begin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../iterator/begin.html">std::begin</a></span><span class="p">(</span><span class="n">out</span><span class="p">);</span>
<span class="w">  </span><span class="k">auto</span><span class="w"> </span><span class="n">end</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../iterator/end.html">std::end</a></span><span class="p">(</span><span class="n">out</span><span class="p">);</span>
<span class="w">  </span><span class="c1">//(1) 10進数文字列へ変換</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::to_chars</span></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p">);</span><span class="w"> </span><span class="n">ec</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n"><a href="../system_error/errc.html">std::errc</a></span><span class="p">{})</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(1) 2進数文字列へ変換</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::to_chars</span></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="mi">65535</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">);</span><span class="w"> </span><span class="n">ec</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n"><a href="../system_error/errc.html">std::errc</a></span><span class="p">{})</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(1) 36進数文字列へ変換</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::to_chars</span></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="mi">35</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p">);</span><span class="w"> </span><span class="n">ec</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n"><a href="../system_error/errc.html">std::errc</a></span><span class="p">{})</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//リウヴィル数</span>
<span class="w">  </span><span class="k">constexpr</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">l</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.11000100000000000000000100000000000</span><span class="p">;</span>
<span class="w">  </span><span class="c1">//(3) 精度・フォーマット指定なしの浮動小数点数変換</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::to_chars</span></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">);</span><span class="w"> </span><span class="n">ec</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n"><a href="../system_error/errc.html">std::errc</a></span><span class="p">{})</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(7) 精度指定なしの浮動小数点数変換、指数表記</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::to_chars</span></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="chars_format.html">std::chars_format</a></span><span class="o">::</span><span class="n">scientific</span><span class="p">);</span><span class="w"> </span><span class="n">ec</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n"><a href="../system_error/errc.html">std::errc</a></span><span class="p">{})</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(7) 精度指定なしの浮動小数点数変換、固定小数表記</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::to_chars</span></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="chars_format.html">std::chars_format</a></span><span class="o">::</span><span class="n">fixed</span><span class="p">);</span><span class="w"> </span><span class="n">ec</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n"><a href="../system_error/errc.html">std::errc</a></span><span class="p">{})</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(7) 精度指定なしの浮動小数点数変換、16進指数表記</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::to_chars</span></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="chars_format.html">std::chars_format</a></span><span class="o">::</span><span class="n">hex</span><span class="p">);</span><span class="w"> </span><span class="n">ec</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n"><a href="../system_error/errc.html">std::errc</a></span><span class="p">{})</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(11) 精度指定ありの浮動小数点数変換、指数表記</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::to_chars</span></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="chars_format.html">std::chars_format</a></span><span class="o">::</span><span class="n">scientific</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p">);</span><span class="w"> </span><span class="n">ec</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n"><a href="../system_error/errc.html">std::errc</a></span><span class="p">{})</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(11) 精度指定ありの浮動小数点数変換、固定小数表記</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::to_chars</span></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="chars_format.html">std::chars_format</a></span><span class="o">::</span><span class="n">fixed</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p">);</span><span class="w"> </span><span class="n">ec</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n"><a href="../system_error/errc.html">std::errc</a></span><span class="p">{})</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(11) 精度指定ありの浮動小数点数変換、16進指数表記</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::to_chars</span></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="chars_format.html">std::chars_format</a></span><span class="o">::</span><span class="n">hex</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p">);</span><span class="w"> </span><span class="n">ec</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n"><a href="../system_error/errc.html">std::errc</a></span><span class="p">{})</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="p">}</span>
</code></pre></div>
<h4>出力例（VS2019 16.5 preview 1）</h4>
<p><pre><code>10
1.10001e-01
1.c29068986fcdfp-4
1.c29068986fcdf000p-4
</code></pre></p>
<h3>基本の使用例 (C++26)</h3>
<p><div class="yata" id="648e21f1840110bd3727f4d4a34d11fa6e6cea89"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html">&lt;iostream&gt;</a></span>
<span class="cp">#include <a href="../charconv.html">&lt;charconv&gt;</a></span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="w">  </span><span class="kt">char</span><span class="w"> </span><span class="n">out</span><span class="p">[</span><span class="mi">50</span><span class="p">]{};</span>
<span class="w">  </span><span class="k">auto</span><span class="w"> </span><span class="n">begin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../iterator/begin.html">std::begin</a></span><span class="p">(</span><span class="n">out</span><span class="p">);</span>
<span class="w">  </span><span class="k">auto</span><span class="w"> </span><span class="n">end</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../iterator/end.html">std::end</a></span><span class="p">(</span><span class="n">out</span><span class="p">);</span>
<span class="w">  </span><span class="c1">//(1) 10進数文字列へ変換</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">to_chars</span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p">))</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(1) 2進数文字列へ変換</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">to_chars</span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="mi">65535</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">))</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(1) 36進数文字列へ変換</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">to_chars</span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="mi">35</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p">))</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//リウヴィル数</span>
<span class="w">  </span><span class="k">constexpr</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">l</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.11000100000000000000000100000000000</span><span class="p">;</span>
<span class="w">  </span><span class="c1">//(3) 精度・フォーマット指定なしの浮動小数点数変換</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">to_chars</span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">))</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(7) 精度指定なしの浮動小数点数変換、指数表記</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">to_chars</span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">chars_format</span><span class="o">::</span><span class="n">scientific</span><span class="p">))</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(7) 精度指定なしの浮動小数点数変換、固定小数表記</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">to_chars</span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">chars_format</span><span class="o">::</span><span class="n">fixed</span><span class="p">))</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(7) 精度指定なしの浮動小数点数変換、16進指数表記</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">to_chars</span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">chars_format</span><span class="o">::</span><span class="n">hex</span><span class="p">))</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(11) 精度指定ありの浮動小数点数変換、指数表記</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">to_chars</span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">chars_format</span><span class="o">::</span><span class="n">scientific</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p">))</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(11) 精度指定ありの浮動小数点数変換、固定小数表記</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">to_chars</span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">chars_format</span><span class="o">::</span><span class="n">fixed</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p">))</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//(11) 精度指定ありの浮動小数点数変換、16進指数表記</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">ptr</span><span class="p">,</span><span class="w"> </span><span class="n">ec</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">to_chars</span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">chars_format</span><span class="o">::</span><span class="n">hex</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p">))</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="p">(</span><span class="n">begin</span><span class="p">,</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">begin</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"conversion failed."</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="p">}</span>
</code></pre></div>
<h4>出力例</h4>
<p><pre><code>10
1.10001e-01
1.c29068986fcdfp-4
1.c29068986fcdf000p-4
</code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<li>C++17</li>
<h3>処理系</h3>
<li><a href="../../implementation.html#clang">Clang</a>: 7.0(整数のみ) <span aria-label="検証済" role="img" title="検証済">✅</span>, 14.0(full support ※) <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<li><a href="../../implementation.html#gcc">GCC</a>: 8.0(整数のみ) <span aria-label="検証済" role="img" title="検証済">✅</span>, 11.1(full support) <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<li><a href="../../implementation.html#visual_cpp">Visual C++</a>: 2017 update 7(整数のみ) <span aria-label="検証済" role="img" title="検証済">✅</span>, update 9(full support) <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<p>※ Clangの実装では、(8), (12)は第３引数のlong double変数が関数内でdouble型に変換される。</p>
<h2>関連項目</h2>
<li><code><a href="chars_format.html">chars_format</a></code></li>
<li><code><a href="to_chars_result.html">to_chars_result</a></code></li>
<li><code><a href="from_chars.html">from_chars</a></code></li>
<li><a href="../../lang/cpp26/structured_binding_declaration_as_a_condition.html">C++26 条件式での構造化束縛の使用を許可</a></li>
<h2>参照</h2>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0067r5.html" target="_blank">P0067R5: Elementary string conversions, revision 5</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0682r1.html" target="_blank">P0682R1: Repairing elementary string conversions</a></li>
<li><a href="https://wg21.cmeerw.net/lwg/issue3266" target="_blank">LWG Issue 3266. <code>to_chars(bool)</code> should be deleted</a></li>
<li><a href="https://docs.microsoft.com/en-us/visualstudio/releasenotes/vs2017-relnotes#-c" target="_blank">Visual Studio 2017 version 15.9.0 - Visual Studio 2017 version 15.9 Release Notes</a></li>
<li><a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2291r3.pdf" target="_blank">P2291R3: Add Constexpr Modifiers to Functions to_chars and from_chars for Integral Types in <code>&lt;charconv&gt;</code> Header</a><ul>
<li>C++23での(1)constexpr指定</li>
<li><a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p1467r9.html" target="_blank">P1467R9 Extended floating-point types and standard names</a><ul>
<li>C++23で<a class="cpprefjp-defined-word" data-desc="&lt;stdfloat&gt;で定義される内部表現の規定された浮動小数点数型" href="../stdfloat.html">拡張浮動小数点数型</a>に対応した</li>
<li><a href="https://ja.cppreference.com/w/c/io/fprintf" target="_blank">C言語リファレンス - fprintf</a></li>
</ul></div>
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