{"id":1989,"date":"2025-03-24T08:48:35","date_gmt":"2025-03-23T23:48:35","guid":{"rendered":"https:\/\/dexall.co.jp\/articles\/?p=1989"},"modified":"2025-03-24T08:48:59","modified_gmt":"2025-03-23T23:48:59","slug":"stdvariant%e3%81%a7%e5%ae%9f%e7%8f%be%e3%81%99%e3%82%8b%e5%9e%8b%e5%ae%89%e5%85%a8%e3%81%aac%e3%83%97%e3%83%ad%e3%82%b0%e3%83%a9%e3%83%9f%e3%83%b3%e3%82%b0%ef%bc%9a%e5%ae%9f%e8%b7%b5%e7%9a%84","status":"publish","type":"post","link":"https:\/\/dexall.co.jp\/articles\/?p=1989","title":{"rendered":"std::variant\u3067\u5b9f\u73fe\u3059\u308b\u578b\u5b89\u5168\u306aC++\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\uff1a\u5b9f\u8df5\u7684\u306a7\u3064\u306e\u4f7f\u7528\u4f8b\u3068\u6ce8\u610f\u70b9"},"content":{"rendered":"\n<div class=\"toc\"><br \/>\n<b>Warning<\/b>:  Undefined array key \"is_admin\" in <b>\/home\/xs392991\/dexall.co.jp\/public_html\/articles\/wp-content\/themes\/sango-theme\/library\/gutenberg\/dist\/classes\/Toc.php<\/b> on line <b>116<\/b><br \/>\n<br \/>\n<b>Warning<\/b>:  Undefined array key \"is_category_top\" in <b>\/home\/xs392991\/dexall.co.jp\/public_html\/articles\/wp-content\/themes\/sango-theme\/library\/gutenberg\/dist\/classes\/Toc.php<\/b> on line <b>121<\/b><br \/>\n<br \/>\n<b>Warning<\/b>:  Undefined array key \"is_top\" in <b>\/home\/xs392991\/dexall.co.jp\/public_html\/articles\/wp-content\/themes\/sango-theme\/library\/gutenberg\/dist\/classes\/Toc.php<\/b> on line <b>128<\/b><br \/>\n    <div id=\"toc_container\" class=\"sgb-toc--bullets js-smooth-scroll\" data-dialog-title=\"\u76ee\u6b21\">\n      <p class=\"toc_title\">\u76ee\u6b21 <\/p>\n      <ul class=\"toc_list\">  <li class=\"first\">    <a href=\"#i-0\">std::variant\u3068\u306f\uff1a\u30e2\u30c0\u30f3C++\u304c\u63d0\u4f9b\u3059\u308b\u578b\u5b89\u5168\u306a\u9078\u629e\u80a2<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-1\">\u5f93\u6765\u306eunion\u3068\u6bd4\u8f03\u3057\u305fstd::variant\u306e\u512a\u4f4d\u6027<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-2\">std::variant\u304c\u89e3\u6c7a\u3059\u308b3\u3064\u306e\u91cd\u8981\u306a\u8ab2\u984c<\/a>      <\/li>    <\/ul>  <\/li>  <li>    <a href=\"#i-3\">std::variant\u306e\u57fa\u672c\u7684\u306a\u4f7f\u3044\u65b9\u30de\u30b9\u30bf\u30fc\u30ac\u30a4\u30c9<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-4\">std::variant\u306e\u5ba3\u8a00\u3068\u521d\u671f\u5316\u30c6\u30af\u30cb\u30c3\u30af<\/a>      <\/li>      <li>        <a href=\"#i-5\">std::get\u95a2\u6570\u3092\u4f7f\u7528\u3057\u305f\u5b89\u5168\u306a\u5024\u306e\u53d6\u5f97\u65b9\u6cd5<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-6\">std::visit\u306b\u3088\u308b\u52b9\u7387\u7684\u306a\u578b\u5206\u5c90\u306e\u5b9f\u88c5<\/a>      <\/li>    <\/ul>  <\/li>  <li>    <a href=\"#i-7\">\u5b9f\u8df5\u7684\u306astd::variant\u6d3b\u7528\u30b7\u30fc\u30f3<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-8\">\u30b9\u30c6\u30fc\u30c8\u7ba1\u7406\u306b\u304a\u3051\u308bstd::variant\u306e\u6d3b\u7528\u6cd5<\/a>      <\/li>      <li>        <a href=\"#i-9\">\u30a8\u30e9\u30fc\u30cf\u30f3\u30c9\u30ea\u30f3\u30b0\u3067\u306estd::variant\u306e\u4f7f\u7528\u4f8b<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-10\">\u30c7\u30fc\u30bf\u69cb\u9020\u8a2d\u8a08\u306b\u304a\u3051\u308bstd::variant\u306e\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9<\/a>      <\/li>    <\/ul>  <\/li>  <li>    <a href=\"#i-11\">std::variant\u306e\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u3068\u6700\u9069\u5316\u30c6\u30af\u30cb\u30c3\u30af<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-12\">\u30e1\u30e2\u30ea\u4f7f\u7528\u91cf\u306e\u6700\u9069\u5316\u65b9\u6cd5<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-13\">\u5b9f\u884c\u6642\u30aa\u30fc\u30d0\u30fc\u30d8\u30c3\u30c9\u306e\u524a\u6e1b\u6226\u7565<\/a>      <\/li>    <\/ul>  <\/li>  <li>    <a href=\"#i-14\">std::variant\u306e\u5b9f\u88c5\u306b\u304a\u3051\u308b\u6ce8\u610f\u70b9\u3068\u843d\u3068\u3057\u7a74<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-15\">\u30e1\u30e2\u30ea\u30a2\u30e9\u30a4\u30e1\u30f3\u30c8\u306b\u95a2\u3059\u308b\u8003\u616e\u4e8b\u9805<\/a>      <\/li>      <li>        <a href=\"#i-16\">\u4f8b\u5916\u5b89\u5168\u6027\u3092\u78ba\u4fdd\u3059\u308b\u305f\u3081\u306e\u5b9f\u88c5\u65b9\u6cd5<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-17\">\u30b3\u30f3\u30d1\u30a4\u30e9\u5225\u306e\u52d5\u4f5c\u306e\u9055\u3044\u3068\u5bfe\u51e6\u6cd5<\/a>      <\/li>    <\/ul>  <\/li>  <li>    <a href=\"#i-18\">std::variant\u3092\u4f7f\u7528\u3057\u305f\u30b3\u30fc\u30c9\u306e\u4fdd\u5b88\u6027\u5411\u4e0a\u30c6\u30af\u30cb\u30c3\u30af<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-19\">\u53ef\u8aad\u6027\u306e\u9ad8\u3044visitor\u5b9f\u88c5\u30d1\u30bf\u30fc\u30f3<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-20\">\u30e6\u30cb\u30c3\u30c8\u30c6\u30b9\u30c8\u3067\u306estd::variant\u306e\u6271\u3044\u65b9<\/a>      <\/li>    <\/ul>  <\/li>  <li class=\"last\">    <a href=\"#i-21\">\u767a\u5c55\u7684\u306astd::variant\u6d3b\u7528\u30c6\u30af\u30cb\u30c3\u30af<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-22\">\u518d\u5e30\u7684\u306avisitor\u30d1\u30bf\u30fc\u30f3\u306e\u5b9f\u88c5\u65b9\u6cd5<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-23\">\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30e1\u30bf\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u3068\u306e\u7d44\u307f\u5408\u308f\u305b\u4f8b<\/a>      <\/li>    <\/ul>  <\/li><\/ul>\n      <a href=\"#\" class=\"sgb-toc-button js-toc-button\" rel=\"nofollow\" data-open-dialog=\"true\"><i class=\"fa fa-list\"><\/i><span class=\"sgb-toc-button__text\">\u76ee\u6b21\u3078<\/span><\/a>\n    <\/div><\/div><h2 class=\"wp-block-heading\" id=\"i-0\">std::variant\u3068\u306f\uff1a\u30e2\u30c0\u30f3C++\u304c\u63d0\u4f9b\u3059\u308b\u578b\u5b89\u5168\u306a\u9078\u629e\u80a2<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">C++17\u3067\u5c0e\u5165\u3055\u308c\u305f<code>std::variant<\/code>\u306f\u3001\u578b\u5b89\u5168\u306a\u5171\u7528\u4f53\uff08union\uff09\u3092\u5b9f\u73fe\u3059\u308b\u6a19\u6e96\u30e9\u30a4\u30d6\u30e9\u30ea\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3067\u3059\u3002\u5f93\u6765\u306eunion\u304c\u6301\u3064\u578b\u5b89\u5168\u6027\u306e\u554f\u984c\u3092\u89e3\u6c7a\u3057\u3001\u3088\u308a\u5b89\u5168\u3067\u30e2\u30c0\u30f3\u306aC++\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u3092\u53ef\u80fd\u306b\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-1\">\u5f93\u6765\u306eunion\u3068\u6bd4\u8f03\u3057\u305fstd::variant\u306e\u512a\u4f4d\u6027<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u5f93\u6765\u306eunion\u306b\u306f\u4ee5\u4e0b\u306e\u3088\u3046\u306a\u554f\u984c\u304c\u3042\u308a\u307e\u3057\u305f\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">union ValueHolder {\n    int intValue;\n    float floatValue;\n    std::string strValue;  \/\/ \u554f\u984c\uff1a\u975e\u30c8\u30ea\u30d3\u30a2\u30eb\u306a\u578b\u306f\u4f7f\u7528\u4e0d\u53ef\n};<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u308c\u306b\u5bfe\u3057\u3001std::variant\u306f\u4ee5\u4e0b\u306e\u3088\u3046\u306a\u5229\u70b9\u3092\u63d0\u4f9b\u3057\u307e\u3059\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ std::variant\u306e\u57fa\u672c\u7684\u306a\u4f7f\u7528\u4f8b\n#include &lt;variant&gt;\n#include &lt;string&gt;\n\nstd::variant&lt;int, float, std::string&gt; modernValue;\nmodernValue = 42;                    \/\/ int\u578b\u3068\u3057\u3066\u521d\u671f\u5316\nmodernValue = std::string(\"Hello\");  \/\/ \u6587\u5b57\u5217\u578b\u306b\u5909\u66f4\u53ef\u80fd<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u4e3b\u306a\u512a\u4f4d\u6027\uff1a<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u578b\u5b89\u5168\u6027\u306e\u4fdd\u8a3c<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u30a2\u30af\u30c6\u30a3\u30d6\u306a\u578b\u306e\u8ffd\u8de1\u304c\u81ea\u52d5\u7684\u306b\u884c\u308f\u308c\u308b<\/li>\n\n\n\n<li>\u4e0d\u6b63\u306a\u30a2\u30af\u30bb\u30b9\u3092\u9632\u3050\u578b\u30c1\u30a7\u30c3\u30af\u304c\u7d44\u307f\u8fbc\u307e\u308c\u3066\u3044\u308b<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u975e\u30c8\u30ea\u30d3\u30a2\u30eb\u306a\u578b\u306e\u30b5\u30dd\u30fc\u30c8<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u30af\u30e9\u30b9\u3084\u30ab\u30b9\u30bf\u30e0\u578b\u3092\u542b\u3080\u4efb\u610f\u306e\u578b\u3092\u4fdd\u6301\u53ef\u80fd<\/li>\n\n\n\n<li>\u30c7\u30b9\u30c8\u30e9\u30af\u30bf\u306e\u9069\u5207\u306a\u547c\u3073\u51fa\u3057\u304c\u4fdd\u8a3c\u3055\u308c\u308b<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u4f8b\u5916\u5b89\u5168\u6027\u306e\u78ba\u4fdd<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u578b\u5909\u63db\u6642\u306e\u4f8b\u5916\u304c\u9069\u5207\u306b\u51e6\u7406\u3055\u308c\u308b<\/li>\n\n\n\n<li>\u30ea\u30bd\u30fc\u30b9\u30ea\u30fc\u30af\u3092\u9632\u3050RAII\u306e\u6069\u6075\u3092\u53d7\u3051\u3089\u308c\u308b<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-2\">std::variant\u304c\u89e3\u6c7a\u3059\u308b3\u3064\u306e\u91cd\u8981\u306a\u8ab2\u984c<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u578b\u5b89\u5168\u6027\u306e\u6b20\u5982<\/strong><\/li>\n<\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ \u5f93\u6765\u306eunion\u3067\u306e\u5371\u967a\u306a\u4f7f\u7528\u4f8b\nunion OldUnion {\n    int i;\n    float f;\n};\n\nOldUnion u;\nu.i = 42;\nfloat f = u.f;  \/\/ \u672a\u5b9a\u7fa9\u52d5\u4f5c\uff1a\u8aa4\u3063\u305f\u578b\u3067\u30a2\u30af\u30bb\u30b9\n\n\/\/ std::variant\u3067\u306e\u5b89\u5168\u306a\u4f7f\u7528\u4f8b\nstd::variant&lt;int, float&gt; v = 42;\ntry {\n    float f = std::get&lt;float&gt;(v);  \/\/ \u4f8b\u5916\uff1a\u4e0d\u6b63\u306a\u30a2\u30af\u30bb\u30b9\u3092\u691c\u51fa\n} catch (const std::bad_variant_access&amp; e) {\n    std::cerr &lt;&lt; \"\u4e0d\u6b63\u306a\u578b\u30a2\u30af\u30bb\u30b9\" &lt;&lt; std::endl;\n}<\/pre>\n\n\n\n<ol start=\"2\" class=\"wp-block-list\">\n<li><strong>\u72b6\u614b\u7ba1\u7406\u306e\u8907\u96d1\u3055<\/strong><\/li>\n<\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ std::variant\u306b\u3088\u308b\u660e\u793a\u7684\u306a\u72b6\u614b\u7ba1\u7406\nstd::variant&lt;int, std::string, std::vector&lt;int&gt;&gt; state;\nstate = std::vector&lt;int&gt;{1, 2, 3};\n\n\/\/ \u578b\u306e\u78ba\u8a8d\u304c\u53ef\u80fd\nif (std::holds_alternative&lt;std::vector&lt;int&gt;&gt;(state)) {\n    auto&amp; vec = std::get&lt;std::vector&lt;int&gt;&gt;(state);\n    \/\/ \u5b89\u5168\u306b\u64cd\u4f5c\u53ef\u80fd\n}<\/pre>\n\n\n\n<ol start=\"3\" class=\"wp-block-list\">\n<li><strong>\u30d3\u30b8\u30bf\u30fc\u30d1\u30bf\u30fc\u30f3\u306e\u5b9f\u88c5\u306e\u7169\u96d1\u3055<\/strong><\/li>\n<\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ std::visit\u3092\u4f7f\u7528\u3057\u305f\u578b\u306b\u5fdc\u3058\u305f\u51e6\u7406\nstd::variant&lt;int, std::string&gt; value = \"Hello\";\n\nstd::visit([](const auto&amp; val) {\n    using T = std::decay_t&lt;decltype(val)&gt;;\n    if constexpr (std::is_same_v&lt;T, int&gt;) {\n        std::cout &lt;&lt; \"\u6574\u6570\u5024: \" &lt;&lt; val &lt;&lt; std::endl;\n    } else if constexpr (std::is_same_v&lt;T, std::string&gt;) {\n        std::cout &lt;&lt; \"\u6587\u5b57\u5217: \" &lt;&lt; val &lt;&lt; std::endl;\n    }\n}, value);<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">std::variant\u306e\u5c0e\u5165\u306b\u3088\u308a\u3001C++\u30d7\u30ed\u30b0\u30e9\u30de\u30fc\u306f\u578b\u5b89\u5168\u6027\u3092\u7dad\u6301\u3057\u306a\u304c\u3089\u3001\u67d4\u8edf\u306a\u5024\u306e\u4fdd\u6301\u3068\u64cd\u4f5c\u304c\u53ef\u80fd\u306b\u306a\u308a\u307e\u3057\u305f\u3002\u7279\u306b\u5927\u898f\u6a21\u306a\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u3084\u30e9\u30a4\u30d6\u30e9\u30ea\u958b\u767a\u306b\u304a\u3044\u3066\u3001\u30b3\u30fc\u30c9\u306e\u4fdd\u5b88\u6027\u3068\u4fe1\u983c\u6027\u3092\u5927\u304d\u304f\u5411\u4e0a\u3055\u305b\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u306e\u57fa\u76e4\u7684\u306a\u7406\u89e3\u306e\u4e0a\u306b\u3001\u6b21\u7bc0\u304b\u3089\u5177\u4f53\u7684\u306a\u4f7f\u7528\u65b9\u6cd5\u3068\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\u306b\u3064\u3044\u3066\u8a73\u3057\u304f\u898b\u3066\u3044\u304d\u307e\u3057\u3087\u3046\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"i-3\">std::variant\u306e\u57fa\u672c\u7684\u306a\u4f7f\u3044\u65b9\u30de\u30b9\u30bf\u30fc\u30ac\u30a4\u30c9<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-4\">std::variant\u306e\u5ba3\u8a00\u3068\u521d\u671f\u5316\u30c6\u30af\u30cb\u30c3\u30af<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">std::variant\u306e\u57fa\u672c\u7684\u306a\u5ba3\u8a00\u3068\u521d\u671f\u5316\u306b\u306f\u3001\u8907\u6570\u306e\u30a2\u30d7\u30ed\u30fc\u30c1\u304c\u5b58\u5728\u3057\u307e\u3059\u3002\u4ee5\u4e0b\u306b\u4e3b\u8981\u306a\u30d1\u30bf\u30fc\u30f3\u3092\u793a\u3057\u307e\u3059\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;string&gt;\n#include &lt;iostream&gt;\n\n\/\/ \u57fa\u672c\u7684\u306a\u5ba3\u8a00\u30d1\u30bf\u30fc\u30f3\nstd::variant&lt;int, std::string, double&gt; v1;          \/\/ \u30c7\u30d5\u30a9\u30eb\u30c8\u3067\u306f\u7b2c\u4e00\u306e\u578b\u3067\u521d\u671f\u5316\nstd::variant&lt;int, std::string&gt; v2{\"Hello\"};         \/\/ \u76f4\u63a5\u521d\u671f\u5316\nstd::variant&lt;std::string, int&gt; v3{42};              \/\/ \u578b\u63a8\u8ad6\u306b\u3088\u308b\u521d\u671f\u5316\n\n\/\/ \u30e2\u30ce\u30b9\u30c6\u30fc\u30c8\uff08\u5358\u4e00\u306e\u5024\u306e\u307f\u3092\u6301\u3064\uff09\u30d1\u30bf\u30fc\u30f3\nstd::variant&lt;std::monostate, std::string&gt; v4;       \/\/ \u521d\u671f\u72b6\u614b\u3092\u8868\u73fe\n\n\/\/ \u521d\u671f\u5316\u5f8c\u306e\u5024\u306e\u5909\u66f4\nvoid demonstrate_initialization() {\n    std::variant&lt;int, std::string&gt; value = 42;\n    std::cout &lt;&lt; std::get&lt;int&gt;(value) &lt;&lt; std::endl;  \/\/ \u51fa\u529b: 42\n\n    value = \"\u5909\u66f4\u5f8c\";\n    std::cout &lt;&lt; std::get&lt;std::string&gt;(value) &lt;&lt; std::endl;  \/\/ \u51fa\u529b: \u5909\u66f4\u5f8c\n}<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-5\">std::get\u95a2\u6570\u3092\u4f7f\u7528\u3057\u305f\u5b89\u5168\u306a\u5024\u306e\u53d6\u5f97\u65b9\u6cd5<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">std::variant\u304b\u3089\u5024\u3092\u53d6\u5f97\u3059\u308b\u969b\u306f\u3001\u8907\u6570\u306e\u65b9\u6cd5\u304c\u7528\u610f\u3055\u308c\u3066\u3044\u307e\u3059\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;string&gt;\n#include &lt;iostream&gt;\n\nvoid demonstrate_value_access() {\n    std::variant&lt;int, std::string, double&gt; value = 3.14;\n\n    \/\/ 1. \u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306b\u3088\u308b\u30a2\u30af\u30bb\u30b9\n    try {\n        double d = std::get&lt;2&gt;(value);  \/\/ \u30a4\u30f3\u30c7\u30c3\u30af\u30b92\uff08double\uff09\u306e\u5024\u3092\u53d6\u5f97\n        std::cout &lt;&lt; \"\u5024: \" &lt;&lt; d &lt;&lt; std::endl;\n    } catch (const std::bad_variant_access&amp; e) {\n        std::cerr &lt;&lt; \"\u7121\u52b9\u306a\u30a2\u30af\u30bb\u30b9\" &lt;&lt; std::endl;\n    }\n\n    \/\/ 2. \u578b\u306b\u3088\u308b\u30a2\u30af\u30bb\u30b9\n    if (auto pval = std::get_if&lt;double&gt;(&amp;value)) {\n        std::cout &lt;&lt; \"double\u5024: \" &lt;&lt; *pval &lt;&lt; std::endl;\n    }\n\n    \/\/ 3. \u578b\u30c1\u30a7\u30c3\u30af\n    if (std::holds_alternative&lt;double&gt;(value)) {\n        std::cout &lt;&lt; \"\u73fe\u5728double\u3092\u4fdd\u6301\u4e2d\" &lt;&lt; std::endl;\n    }\n}<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-6\">std::visit\u306b\u3088\u308b\u52b9\u7387\u7684\u306a\u578b\u5206\u5c90\u306e\u5b9f\u88c5<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">std::visit\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u3067\u3001\u578b\u306b\u5fdc\u3058\u305f\u51e6\u7406\u3092\u52b9\u7387\u7684\u306b\u5b9f\u88c5\u3067\u304d\u307e\u3059\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;string&gt;\n#include &lt;iostream&gt;\n\n\/\/ \u57fa\u672c\u7684\u306a\u30d3\u30b8\u30bf\u30fc\u30d1\u30bf\u30fc\u30f3\nvoid basic_visitor_example() {\n    std::variant&lt;int, std::string, double&gt; value = \"Hello\";\n\n    std::visit([](const auto&amp; val) {\n        using T = std::decay_t&lt;decltype(val)&gt;;\n        if constexpr (std::is_same_v&lt;T, int&gt;) {\n            std::cout &lt;&lt; \"\u6574\u6570: \" &lt;&lt; val &lt;&lt; std::endl;\n        } else if constexpr (std::is_same_v&lt;T, std::string&gt;) {\n            std::cout &lt;&lt; \"\u6587\u5b57\u5217: \" &lt;&lt; val &lt;&lt; std::endl;\n        } else if constexpr (std::is_same_v&lt;T, double&gt;) {\n            std::cout &lt;&lt; \"\u6d6e\u52d5\u5c0f\u6570\u70b9: \" &lt;&lt; val &lt;&lt; std::endl;\n        }\n    }, value);\n}\n\n\/\/ \u69cb\u9020\u5316\u3055\u308c\u305f\u30d3\u30b8\u30bf\u30fc\u306e\u5b9f\u88c5\nstruct ValuePrinter {\n    void operator()(int value) const { \n        std::cout &lt;&lt; \"\u6574\u6570\u5024: \" &lt;&lt; value &lt;&lt; std::endl; \n    }\n    void operator()(const std::string&amp; value) const { \n        std::cout &lt;&lt; \"\u6587\u5b57\u5217\u5024: \" &lt;&lt; value &lt;&lt; std::endl; \n    }\n    void operator()(double value) const { \n        std::cout &lt;&lt; \"\u6d6e\u52d5\u5c0f\u6570\u70b9\u5024: \" &lt;&lt; value &lt;&lt; std::endl; \n    }\n};\n\nvoid structured_visitor_example() {\n    std::variant&lt;int, std::string, double&gt; value = 42;\n    std::visit(ValuePrinter{}, value);\n}\n\n\/\/ \u5024\u306e\u5909\u63db\u3092\u884c\u3046\u30d3\u30b8\u30bf\u30fc\u30d1\u30bf\u30fc\u30f3\ntemplate&lt;typename T&gt;\nstruct ToStringConverter {\n    std::string operator()(const T&amp; value) const {\n        return std::to_string(value);\n    }\n    std::string operator()(const std::string&amp; value) const {\n        return value;\n    }\n};\n\nvoid converter_example() {\n    std::variant&lt;int, std::string, double&gt; value = 3.14;\n    std::string result = std::visit(ToStringConverter&lt;double&gt;{}, value);\n    std::cout &lt;&lt; \"\u5909\u63db\u7d50\u679c: \" &lt;&lt; result &lt;&lt; std::endl;\n}<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u308c\u3089\u306e\u57fa\u672c\u7684\u306a\u4f7f\u3044\u65b9\u3092\u7406\u89e3\u3059\u308b\u3053\u3068\u3067\u3001std::variant\u3092\u52b9\u679c\u7684\u306b\u6d3b\u7528\u3067\u304d\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002\u6b21\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u306f\u3001\u3053\u308c\u3089\u306e\u57fa\u672c\u30c6\u30af\u30cb\u30c3\u30af\u3092\u6d3b\u7528\u3057\u305f\u5b9f\u8df5\u7684\u306a\u4f7f\u7528\u4f8b\u3092\u898b\u3066\u3044\u304d\u307e\u3057\u3087\u3046\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u5b9f\u88c5\u6642\u306e\u91cd\u8981\u306a\u30dd\u30a4\u30f3\u30c8\uff1a<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u578b\u5b89\u5168\u6027\u306e\u7dad\u6301<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u5e38\u306bstd::get_if\u3084std::holds_alternative\u3092\u4f7f\u7528\u3057\u3066\u578b\u30c1\u30a7\u30c3\u30af\u3092\u884c\u3046<\/li>\n\n\n\n<li>\u4f8b\u5916\u51e6\u7406\u3092\u9069\u5207\u306b\u5b9f\u88c5\u3059\u308b<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u306e\u8003\u616e<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u4e0d\u5fc5\u8981\u306a\u578b\u5909\u63db\u3092\u907f\u3051\u308b<\/li>\n\n\n\n<li>\u30d3\u30b8\u30bf\u30fc\u30d1\u30bf\u30fc\u30f3\u3092\u52b9\u7387\u7684\u306b\u5b9f\u88c5\u3059\u308b<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u30b3\u30fc\u30c9\u306e\u53ef\u8aad\u6027<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u660e\u78ba\u306a\u547d\u540d\u898f\u5247\u3092\u4f7f\u7528\u3059\u308b<\/li>\n\n\n\n<li>\u9069\u5207\u306a\u30b3\u30e1\u30f3\u30c8\u3092\u8ffd\u52a0\u3059\u308b<\/li>\n\n\n\n<li>\u69cb\u9020\u5316\u3055\u308c\u305f\u30d3\u30b8\u30bf\u30fc\u30d1\u30bf\u30fc\u30f3\u3092\u4f7f\u7528\u3059\u308b<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u308c\u3089\u306e\u57fa\u672c\u539f\u5247\u3092\u5b88\u308b\u3053\u3068\u3067\u3001\u4fdd\u5b88\u6027\u304c\u9ad8\u304f\u3001\u52b9\u7387\u7684\u306a\u30b3\u30fc\u30c9\u3092\u5b9f\u88c5\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"i-7\">\u5b9f\u8df5\u7684\u306astd::variant\u6d3b\u7528\u30b7\u30fc\u30f3<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u5b9f\u52d9\u3067\u306e\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u306b\u304a\u3044\u3066\u3001std::variant\u306f\u69d8\u3005\u306a\u5834\u9762\u3067\u6d3b\u7528\u3067\u304d\u307e\u3059\u3002\u672c\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u306f\u3001\u5177\u4f53\u7684\u306a\u30e6\u30fc\u30b9\u30b1\u30fc\u30b9\u3068\u5b9f\u88c5\u4f8b\u3092\u7d39\u4ecb\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-8\">\u30b9\u30c6\u30fc\u30c8\u7ba1\u7406\u306b\u304a\u3051\u308bstd::variant\u306e\u6d3b\u7528\u6cd5<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u30b9\u30c6\u30fc\u30c8\u30de\u30b7\u30f3\u3084UI\u72b6\u614b\u306e\u7ba1\u7406\u306b\u304a\u3044\u3066\u3001std::variant\u306f\u578b\u5b89\u5168\u306a\u72b6\u614b\u7ba1\u7406\u3092\u5b9f\u73fe\u3057\u307e\u3059\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;string&gt;\n#include &lt;iostream&gt;\n\n\/\/ UI\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u72b6\u614b\u3092\u8868\u73fe\nstruct LoadingState {\n    std::string message;\n};\n\nstruct ErrorState {\n    std::string errorMessage;\n    int errorCode;\n};\n\nstruct SuccessState {\n    std::vector&lt;std::string&gt; data;\n};\n\nclass UIComponent {\npublic:\n    using State = std::variant&lt;LoadingState, ErrorState, SuccessState&gt;;\n\n    void updateState(const State&amp; newState) {\n        state = newState;\n        renderUI();\n    }\n\nprivate:\n    void renderUI() {\n        std::visit(\n            [](const auto&amp; s) {\n                using T = std::decay_t&lt;decltype(s)&gt;;\n                if constexpr (std::is_same_v&lt;T, LoadingState&gt;) {\n                    std::cout &lt;&lt; \"Loading: \" &lt;&lt; s.message &lt;&lt; std::endl;\n                } else if constexpr (std::is_same_v&lt;T, ErrorState&gt;) {\n                    std::cout &lt;&lt; \"Error \" &lt;&lt; s.errorCode &lt;&lt; \": \" &lt;&lt; s.errorMessage &lt;&lt; std::endl;\n                } else if constexpr (std::is_same_v&lt;T, SuccessState&gt;) {\n                    std::cout &lt;&lt; \"Success! Data items: \" &lt;&lt; s.data.size() &lt;&lt; std::endl;\n                }\n            },\n            state\n        );\n    }\n\n    State state;\n};<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-9\">\u30a8\u30e9\u30fc\u30cf\u30f3\u30c9\u30ea\u30f3\u30b0\u3067\u306estd::variant\u306e\u4f7f\u7528\u4f8b<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Result\u578b\u30d1\u30bf\u30fc\u30f3\u306e\u5b9f\u88c5\u306bstd::variant\u3092\u6d3b\u7528\u3059\u308b\u4f8b\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;string&gt;\n#include &lt;optional&gt;\n\ntemplate&lt;typename T, typename E = std::string&gt;\nclass Result {\nprivate:\n    std::variant&lt;T, E&gt; data;\n\npublic:\n    Result(const T&amp; value) : data(value) {}\n    Result(const E&amp; error) : data(error) {}\n\n    bool isSuccess() const {\n        return std::holds_alternative&lt;T&gt;(data);\n    }\n\n    bool isError() const {\n        return std::holds_alternative&lt;E&gt;(data);\n    }\n\n    std::optional&lt;T&gt; getValue() const {\n        if (const T* value = std::get_if&lt;T&gt;(&amp;data)) {\n            return *value;\n        }\n        return std::nullopt;\n    }\n\n    std::optional&lt;E&gt; getError() const {\n        if (const E* error = std::get_if&lt;E&gt;(&amp;data)) {\n            return *error;\n        }\n        return std::nullopt;\n    }\n};\n\n\/\/ \u4f7f\u7528\u4f8b\nResult&lt;int&gt; divideNumbers(int a, int b) {\n    if (b == 0) {\n        return Result&lt;int&gt;(\"\u9664\u7b97by zero error\");\n    }\n    return Result&lt;int&gt;(a \/ b);\n}<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-10\">\u30c7\u30fc\u30bf\u69cb\u9020\u8a2d\u8a08\u306b\u304a\u3051\u308bstd::variant\u306e\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u8907\u96d1\u306a\u30c7\u30fc\u30bf\u69cb\u9020\u306e\u8a2d\u8a08\u306b\u304a\u3051\u308bstd::variant\u306e\u6d3b\u7528\u4f8b\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;vector&gt;\n#include &lt;string&gt;\n#include &lt;memory&gt;\n\n\/\/ JSON\u30e9\u30a4\u30af\u306a\u5024\u3092\u8868\u73fe\u3059\u308b\u30c7\u30fc\u30bf\u69cb\u9020\nclass JsonValue {\npublic:\n    using Array = std::vector&lt;JsonValue&gt;;\n    using Object = std::map&lt;std::string, JsonValue&gt;;\n    using Value = std::variant&lt;\n        std::nullptr_t,\n        bool,\n        int64_t,\n        double,\n        std::string,\n        Array,\n        Object\n    &gt;;\n\nprivate:\n    Value value;\n\npublic:\n    JsonValue() : value(nullptr) {}\n    template&lt;typename T&gt;\n    JsonValue(T&amp;&amp; v) : value(std::forward&lt;T&gt;(v)) {}\n\n    \/\/ \u578b\u5b89\u5168\u306a\u30a2\u30af\u30bb\u30b5\u30e1\u30bd\u30c3\u30c9\n    template&lt;typename T&gt;\n    const T&amp; get() const {\n        return std::get&lt;T&gt;(value);\n    }\n\n    template&lt;typename T&gt;\n    bool is() const {\n        return std::holds_alternative&lt;T&gt;(value);\n    }\n\n    \/\/ \u30d3\u30b8\u30bf\u30fc\u30d1\u30bf\u30fc\u30f3\u306b\u3088\u308b\u5024\u306e\u51e6\u7406\n    template&lt;typename Visitor&gt;\n    auto visit(Visitor&amp;&amp; visitor) const {\n        return std::visit(std::forward&lt;Visitor&gt;(visitor), value);\n    }\n\n    \/\/ \u6587\u5b57\u5217\u5316\u306e\u4f8b\n    std::string toString() const {\n        return visit([](const auto&amp; v) -&gt; std::string {\n            using T = std::decay_t&lt;decltype(v)&gt;;\n            if constexpr (std::is_same_v&lt;T, std::nullptr_t&gt;) {\n                return \"null\";\n            } else if constexpr (std::is_same_v&lt;T, bool&gt;) {\n                return v ? \"true\" : \"false\";\n            } else if constexpr (std::is_same_v&lt;T, int64_t&gt; || \n                               std::is_same_v&lt;T, double&gt;) {\n                return std::to_string(v);\n            } else if constexpr (std::is_same_v&lt;T, std::string&gt;) {\n                return \"\\\"\" + v + \"\\\"\";\n            } else if constexpr (std::is_same_v&lt;T, Array&gt;) {\n                std::string result = \"[\";\n                for (const auto&amp; elem : v) {\n                    if (result.length() &gt; 1) result += \",\";\n                    result += elem.toString();\n                }\n                return result + \"]\";\n            } else if constexpr (std::is_same_v&lt;T, Object&gt;) {\n                std::string result = \"{\";\n                for (const auto&amp; [key, val] : v) {\n                    if (result.length() &gt; 1) result += \",\";\n                    result += \"\\\"\" + key + \"\\\":\" + val.toString();\n                }\n                return result + \"}\";\n            }\n        });\n    }\n};<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5b9f\u8df5\u7684\u306a\u5b9f\u88c5\u306e\u30dd\u30a4\u30f3\u30c8\uff1a<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u578b\u5b89\u5168\u6027\u306e\u78ba\u4fdd<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>variant\u306e\u578b\u30d1\u30e9\u30e1\u30fc\u30bf\u306f\u614e\u91cd\u306b\u9078\u629e<\/li>\n\n\n\n<li>\u4e0d\u6b63\u306a\u578b\u5909\u63db\u3092\u9632\u3050\u305f\u3081\u306e\u30c1\u30a7\u30c3\u30af\u3092\u5b9f\u88c5<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u30a8\u30e9\u30fc\u30cf\u30f3\u30c9\u30ea\u30f3\u30b0<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u4f8b\u5916\u306b\u983c\u3089\u306a\u3044\u30a8\u30e9\u30fc\u51e6\u7406\u306e\u5b9f\u88c5<\/li>\n\n\n\n<li>Result\u578b\u30d1\u30bf\u30fc\u30f3\u306e\u6d3b\u7528<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u306e\u6700\u9069\u5316<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u4e0d\u5fc5\u8981\u306a\u30b3\u30d4\u30fc\u306e\u56de\u907f<\/li>\n\n\n\n<li>\u30e1\u30e2\u30ea\u52b9\u7387\u306e\u8003\u616e<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u308c\u3089\u306e\u5b9f\u8df5\u4f8b\u306f\u3001std::variant\u306e\u5f37\u529b\u306a\u578b\u5b89\u5168\u6027\u3068\u67d4\u8edf\u6027\u3092\u6d3b\u304b\u3057\u305f\u5b9f\u88c5\u30d1\u30bf\u30fc\u30f3\u3092\u793a\u3057\u3066\u3044\u307e\u3059\u3002\u6b21\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u306f\u3001\u3053\u308c\u3089\u306e\u5b9f\u88c5\u306b\u304a\u3051\u308b\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u3068\u6700\u9069\u5316\u306b\u3064\u3044\u3066\u8a73\u3057\u304f\u898b\u3066\u3044\u304d\u307e\u3057\u3087\u3046\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"i-11\">std::variant\u306e\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u3068\u6700\u9069\u5316\u30c6\u30af\u30cb\u30c3\u30af<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">std::variant\u3092\u52b9\u7387\u7684\u306b\u4f7f\u7528\u3059\u308b\u305f\u3081\u306b\u306f\u3001\u305d\u306e\u30e1\u30e2\u30ea\u4f7f\u7528\u91cf\u3068\u5b9f\u884c\u6642\u30aa\u30fc\u30d0\u30fc\u30d8\u30c3\u30c9\u3092\u7406\u89e3\u3057\u3001\u9069\u5207\u306a\u6700\u9069\u5316\u3092\u884c\u3046\u3053\u3068\u304c\u91cd\u8981\u3067\u3059\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-12\">\u30e1\u30e2\u30ea\u4f7f\u7528\u91cf\u306e\u6700\u9069\u5316\u65b9\u6cd5<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">std::variant\u306e\u30e1\u30e2\u30ea\u30ec\u30a4\u30a2\u30a6\u30c8\u3092\u7406\u89e3\u3057\u3001\u52b9\u7387\u7684\u306b\u4f7f\u7528\u3059\u308b\u65b9\u6cd5\u3092\u898b\u3066\u3044\u304d\u307e\u3057\u3087\u3046\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;string&gt;\n#include &lt;iostream&gt;\n\n\/\/ \u30e1\u30e2\u30ea\u30ec\u30a4\u30a2\u30a6\u30c8\u306e\u78ba\u8a8d\nvoid analyze_memory_layout() {\n    \/\/ \u57fa\u672c\u7684\u306avariant\u306e\u30b5\u30a4\u30ba\n    using SmallVariant = std::variant&lt;int, char&gt;;\n    using StringVariant = std::variant&lt;int, std::string&gt;;\n\n    std::cout &lt;&lt; \"\u30b5\u30a4\u30ba\u6bd4\u8f03:\\n\";\n    std::cout &lt;&lt; \"sizeof(int): \" &lt;&lt; sizeof(int) &lt;&lt; \"\\n\";\n    std::cout &lt;&lt; \"sizeof(SmallVariant): \" &lt;&lt; sizeof(SmallVariant) &lt;&lt; \"\\n\";\n    std::cout &lt;&lt; \"sizeof(StringVariant): \" &lt;&lt; sizeof(StringVariant) &lt;&lt; \"\\n\";\n}\n\n\/\/ \u30e1\u30e2\u30ea\u6700\u9069\u5316\u30c6\u30af\u30cb\u30c3\u30af\nstruct OptimizedState {\n    \/\/ \u5c0f\u3055\u306a\u578b\u3092\u5148\u306b\u914d\u7f6e\u3057\u3066\u30d1\u30c7\u30a3\u30f3\u30b0\u3092\u6700\u5c0f\u5316\n    uint8_t flags;\n    int32_t value;\n    std::string data;\n};\n\nstruct UnoptimizedState {\n    \/\/ \u30d1\u30c7\u30a3\u30f3\u30b0\u304c\u767a\u751f\u3057\u3084\u3059\u3044\u30ec\u30a4\u30a2\u30a6\u30c8\n    std::string data;\n    uint8_t flags;\n    int32_t value;\n};\n\n\/\/ \u6700\u9069\u5316\u3055\u308c\u305fvariant\u306e\u4f7f\u7528\u4f8b\nusing OptimizedVariant = std::variant&lt;\n    int8_t,      \/\/ \u5c0f\u3055\u306a\u578b\u3092\u5148\u306b\u914d\u7f6e\n    int32_t,\n    std::string  \/\/ \u5927\u304d\u306a\u578b\u3092\u5f8c\u308d\u306b\n&gt;;\n\n\/\/ \u30e1\u30e2\u30ea\u30d7\u30fc\u30eb\u3092\u4f7f\u7528\u3057\u305f\u6700\u9069\u5316\u4f8b\ntemplate&lt;typename... Types&gt;\nclass PooledVariant {\n    std::variant&lt;Types...&gt; data;\n    static constexpr size_t MaxSize = std::max({sizeof(Types)...});\n    static thread_local std::array&lt;char, MaxSize&gt; memoryPool;\n\npublic:\n    template&lt;typename T&gt;\n    void set(T&amp;&amp; value) {\n        if constexpr (sizeof(T) &lt;= MaxSize) {\n            \/\/ \u30e1\u30e2\u30ea\u30d7\u30fc\u30eb\u3092\u4f7f\u7528\n            new (&amp;memoryPool[0]) T(std::forward&lt;T&gt;(value));\n            data = *reinterpret_cast&lt;T*&gt;(&amp;memoryPool[0]);\n        } else {\n            data = std::forward&lt;T&gt;(value);\n        }\n    }\n};<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-13\">\u5b9f\u884c\u6642\u30aa\u30fc\u30d0\u30fc\u30d8\u30c3\u30c9\u306e\u524a\u6e1b\u6226\u7565<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">std::variant\u306e\u5b9f\u884c\u6642\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u3092\u6700\u9069\u5316\u3059\u308b\u30c6\u30af\u30cb\u30c3\u30af\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;chrono&gt;\n#include &lt;vector&gt;\n\n\/\/ \u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u6e2c\u5b9a\u7528\u30e6\u30fc\u30c6\u30a3\u30ea\u30c6\u30a3\nclass Timer {\n    using Clock = std::chrono::high_resolution_clock;\n    Clock::time_point start;\npublic:\n    Timer() : start(Clock::now()) {}\n\n    double elapsed() const {\n        auto end = Clock::now();\n        return std::chrono::duration&lt;double&gt;(end - start).count();\n    }\n};\n\n\/\/ \u6700\u9069\u5316\u30c6\u30af\u30cb\u30c3\u30af1: \u578b\u30c1\u30a7\u30c3\u30af\u306e\u6700\u5c0f\u5316\ntemplate&lt;typename T&gt;\nclass OptimizedProcessor {\n    std::variant&lt;int, std::string, double&gt; data;\n\n    \/\/ \u30ad\u30e3\u30c3\u30b7\u30e5\u3055\u308c\u305f\u578b\u60c5\u5831\n    size_t currentType = 0;\n\npublic:\n    void process(const T&amp; value) {\n        \/\/ \u578b\u304c\u5909\u66f4\u3055\u308c\u305f\u5834\u5408\u306e\u307f\u30c1\u30a7\u30c3\u30af\n        if (currentType != data.index()) {\n            currentType = data.index();\n            \/\/ \u578b\u306b\u5fdc\u3058\u305f\u521d\u671f\u5316\u51e6\u7406\n        }\n        \/\/ \u51e6\u7406\u306e\u5b9f\u884c\n    }\n};\n\n\/\/ \u6700\u9069\u5316\u30c6\u30af\u30cb\u30c3\u30af2: \u30a4\u30f3\u30e9\u30a4\u30f3\u5316\u3092\u8003\u616e\u3057\u305fvisitor\nstruct InlinedVisitor {\n    \/\/ \u5c0f\u3055\u306a\u95a2\u6570\u306f\u30a4\u30f3\u30e9\u30a4\u30f3\u5316\u3055\u308c\u3084\u3059\u3044\n    constexpr void operator()(int x) const { \/* \u51e6\u7406 *\/ }\n    constexpr void operator()(double x) const { \/* \u51e6\u7406 *\/ }\n    constexpr void operator()(const std::string&amp; x) const { \/* \u51e6\u7406 *\/ }\n};\n\n\/\/ \u6700\u9069\u5316\u30c6\u30af\u30cb\u30c3\u30af3: \u9759\u7684\u30c7\u30a3\u30b9\u30d1\u30c3\u30c1\u306e\u6d3b\u7528\ntemplate&lt;typename Variant, typename Visitor&gt;\nconstexpr auto optimized_visit(Variant&amp;&amp; variant, Visitor&amp;&amp; visitor) {\n    if constexpr (std::is_same_v&lt;Variant, std::variant&lt;int&gt;&gt;) {\n        return visitor(std::get&lt;0&gt;(variant));\n    } else {\n        return std::visit(std::forward&lt;Visitor&gt;(visitor), \n                         std::forward&lt;Variant&gt;(variant));\n    }\n}\n\n\/\/ \u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u6bd4\u8f03\u306e\u30d9\u30f3\u30c1\u30de\u30fc\u30af\nvoid benchmark_variant_performance() {\n    constexpr size_t ITERATIONS = 1000000;\n    std::variant&lt;int, std::string&gt; v = 42;\n\n    \/\/ \u901a\u5e38\u306e\u30a2\u30af\u30bb\u30b9\n    Timer t1;\n    for (size_t i = 0; i &lt; ITERATIONS; ++i) {\n        if (std::holds_alternative&lt;int&gt;(v)) {\n            auto val = std::get&lt;int&gt;(v);\n        }\n    }\n    double normal_access = t1.elapsed();\n\n    \/\/ \u6700\u9069\u5316\u3055\u308c\u305f\u30a2\u30af\u30bb\u30b9\n    Timer t2;\n    size_t type_index = v.index();\n    for (size_t i = 0; i &lt; ITERATIONS; ++i) {\n        if (type_index == 0) {  \/\/ int\u306e\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\n            auto val = std::get&lt;int&gt;(v);\n        }\n    }\n    double optimized_access = t2.elapsed();\n\n    std::cout &lt;&lt; \"\u901a\u5e38\u306e\u30a2\u30af\u30bb\u30b9\u6642\u9593: \" &lt;&lt; normal_access &lt;&lt; \"\u79d2\\n\";\n    std::cout &lt;&lt; \"\u6700\u9069\u5316\u5f8c\u306e\u30a2\u30af\u30bb\u30b9\u6642\u9593: \" &lt;&lt; optimized_access &lt;&lt; \"\u79d2\\n\";\n}<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u6700\u9069\u5316\u306e\u305f\u3081\u306e\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\uff1a<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u30e1\u30e2\u30ea\u6700\u9069\u5316<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u5c0f\u3055\u306a\u578b\u3092\u5148\u306b\u914d\u7f6e\u3057\u3066\u30d1\u30c7\u30a3\u30f3\u30b0\u3092\u6700\u5c0f\u5316<\/li>\n\n\n\n<li>\u30e1\u30e2\u30ea\u30a2\u30e9\u30a4\u30e1\u30f3\u30c8\u3092\u8003\u616e\u3057\u305f\u578b\u306e\u9806\u5e8f\u4ed8\u3051<\/li>\n\n\n\n<li>\u30b9\u30e2\u30fc\u30eb\u30b9\u30c8\u30ea\u30f3\u30b0\u30aa\u30d7\u30c6\u30a3\u30de\u30a4\u30bc\u30fc\u30b7\u30e7\u30f3\uff08SSO\uff09\u306e\u6d3b\u7528<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u5b9f\u884c\u6642\u30aa\u30fc\u30d0\u30fc\u30d8\u30c3\u30c9\u524a\u6e1b<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u4e0d\u5fc5\u8981\u306a\u578b\u30c1\u30a7\u30c3\u30af\u306e\u56de\u907f<\/li>\n\n\n\n<li>\u52b9\u7387\u7684\u306avisitor\u30d1\u30bf\u30fc\u30f3\u306e\u5b9f\u88c5<\/li>\n\n\n\n<li>\u30a4\u30f3\u30e9\u30a4\u30f3\u5316\u3092\u8003\u616e\u3057\u305f\u8a2d\u8a08<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u30ad\u30e3\u30c3\u30b7\u30e5\u52b9\u7387\u306e\u6539\u5584<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u30c7\u30fc\u30bf\u306e\u30ed\u30fc\u30ab\u30ea\u30c6\u30a3\u3092\u8003\u616e\u3057\u305f\u8a2d\u8a08<\/li>\n\n\n\n<li>\u30ad\u30e3\u30c3\u30b7\u30e5\u30d5\u30ec\u30f3\u30c9\u30ea\u30fc\u306a\u30a2\u30af\u30bb\u30b9\u30d1\u30bf\u30fc\u30f3<\/li>\n\n\n\n<li>false sharing\u306e\u56de\u907f<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u308c\u3089\u306e\u6700\u9069\u5316\u30c6\u30af\u30cb\u30c3\u30af\u3092\u9069\u5207\u306b\u7d44\u307f\u5408\u308f\u305b\u308b\u3053\u3068\u3067\u3001std::variant\u3092\u4f7f\u7528\u3057\u305f\u30b3\u30fc\u30c9\u306e\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u3092\u5927\u5e45\u306b\u6539\u5584\u3067\u304d\u307e\u3059\u3002\u305f\u3060\u3057\u3001\u6700\u9069\u5316\u3092\u884c\u3046\u969b\u306f\u5fc5\u305a\u30d7\u30ed\u30d5\u30a1\u30a4\u30ea\u30f3\u30b0\u3092\u884c\u3044\u3001\u5b9f\u969b\u306e\u6539\u5584\u52b9\u679c\u3092\u78ba\u8a8d\u3059\u308b\u3053\u3068\u304c\u91cd\u8981\u3067\u3059\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"i-14\">std::variant\u306e\u5b9f\u88c5\u306b\u304a\u3051\u308b\u6ce8\u610f\u70b9\u3068\u843d\u3068\u3057\u7a74<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">std::variant\u3092\u52b9\u679c\u7684\u306b\u4f7f\u7528\u3059\u308b\u305f\u3081\u306b\u306f\u3001\u3044\u304f\u3064\u304b\u306e\u91cd\u8981\u306a\u6ce8\u610f\u70b9\u3068\u6f5c\u5728\u7684\u306a\u554f\u984c\u3092\u7406\u89e3\u3059\u308b\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-15\">\u30e1\u30e2\u30ea\u30a2\u30e9\u30a4\u30e1\u30f3\u30c8\u306b\u95a2\u3059\u308b\u8003\u616e\u4e8b\u9805<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u30e1\u30e2\u30ea\u30a2\u30e9\u30a4\u30e1\u30f3\u30c8\u306e\u554f\u984c\u306f\u3001\u7279\u306b\u7570\u306a\u308b\u30a2\u30e9\u30a4\u30e1\u30f3\u30c8\u8981\u4ef6\u3092\u6301\u3064\u578b\u3092\u6271\u3046\u969b\u306b\u91cd\u8981\u3067\u3059\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;iostream&gt;\n\n\/\/ \u30a2\u30e9\u30a4\u30e1\u30f3\u30c8\u8981\u4ef6\u306e\u7570\u306a\u308b\u69cb\u9020\u4f53\nstruct alignas(4) Simple {\n    int x;\n};\n\nstruct alignas(16) Aligned {\n    double x;\n    double y;\n};\n\n\/\/ \u30a2\u30e9\u30a4\u30e1\u30f3\u30c8\u306e\u554f\u984c\u3092\u793a\u3059\u4f8b\nvoid demonstrate_alignment_issues() {\n    \/\/ \u30a2\u30e9\u30a4\u30e1\u30f3\u30c8\u8981\u4ef6\u306e\u78ba\u8a8d\n    std::cout &lt;&lt; \"Simple alignment: \" &lt;&lt; alignof(Simple) &lt;&lt; std::endl;\n    std::cout &lt;&lt; \"Aligned alignment: \" &lt;&lt; alignof(Aligned) &lt;&lt; std::endl;\n\n    \/\/ variant\u306e\u30a2\u30e9\u30a4\u30e1\u30f3\u30c8\n    using V = std::variant&lt;Simple, Aligned&gt;;\n    std::cout &lt;&lt; \"Variant alignment: \" &lt;&lt; alignof(V) &lt;&lt; std::endl;\n\n    \/\/ \u30e1\u30e2\u30ea\u4f7f\u7528\u91cf\u306e\u78ba\u8a8d\n    std::cout &lt;&lt; \"Variant size: \" &lt;&lt; sizeof(V) &lt;&lt; std::endl;\n}\n\n\/\/ \u30a2\u30e9\u30a4\u30e1\u30f3\u30c8\u6700\u9069\u5316\u306e\u4f8b\ntemplate&lt;typename... Types&gt;\nclass AlignmentOptimizedVariant {\n    \/\/ \u6700\u5927\u306e\u30a2\u30e9\u30a4\u30e1\u30f3\u30c8\u8981\u4ef6\u3092\u8a08\u7b97\n    static constexpr size_t MaxAlignment = std::max({alignof(Types)...});\n\n    alignas(MaxAlignment) std::variant&lt;Types...&gt; data;\n\npublic:\n    template&lt;typename T&gt;\n    void set(T&amp;&amp; value) {\n        data = std::forward&lt;T&gt;(value);\n    }\n};<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-16\">\u4f8b\u5916\u5b89\u5168\u6027\u3092\u78ba\u4fdd\u3059\u308b\u305f\u3081\u306e\u5b9f\u88c5\u65b9\u6cd5<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u4f8b\u5916\u5b89\u5168\u6027\u3092\u78ba\u4fdd\u3059\u308b\u305f\u3081\u306e\u91cd\u8981\u306a\u5b9f\u88c5\u30d1\u30bf\u30fc\u30f3\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;memory&gt;\n#include &lt;stdexcept&gt;\n\n\/\/ \u30ea\u30bd\u30fc\u30b9\u7ba1\u7406\u3092\u542b\u3080\u578b\u306e\u4f8b\nclass ResourceHolder {\n    std::unique_ptr&lt;int[]&gt; resource;\n    size_t size;\n\npublic:\n    ResourceHolder(size_t n) : resource(new int[n]), size(n) {}\n\n    \/\/ \u4f8b\u5916\u3092\u6295\u3052\u308b\u53ef\u80fd\u6027\u306e\u3042\u308b\u64cd\u4f5c\n    void process() {\n        if (size == 0) throw std::runtime_error(\"Invalid size\");\n    }\n};\n\n\/\/ \u4f8b\u5916\u5b89\u5168\u306avariant\u306e\u4f7f\u7528\u4f8b\nclass ExceptionSafeVariant {\n    std::variant&lt;int, ResourceHolder, std::string&gt; data;\n\npublic:\n    \/\/ \u4f8b\u5916\u5b89\u5168\u306a\u66f4\u65b0\u64cd\u4f5c\n    template&lt;typename T&gt;\n    void update(T&amp;&amp; value) {\n        \/\/ \u4e00\u6642\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u4f5c\u6210\n        using Type = std::decay_t&lt;T&gt;;\n        Type temp(std::forward&lt;T&gt;(value));\n\n        try {\n            \/\/ \u4e00\u6642\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u304c\u6b63\u5e38\u306b\u69cb\u7bc9\u3055\u308c\u305f\u5f8c\u3067\u66f4\u65b0\n            data = std::move(temp);\n        } catch (...) {\n            \/\/ \u66f4\u65b0\u306b\u5931\u6557\u3057\u305f\u5834\u5408\u3067\u3082\u5143\u306e\u30c7\u30fc\u30bf\u306f\u4fdd\u6301\u3055\u308c\u308b\n            throw;\n        }\n    }\n\n    \/\/ \u4f8b\u5916\u5b89\u5168\u306avisit\u51e6\u7406\n    template&lt;typename Visitor&gt;\n    void visit_safely(Visitor&amp;&amp; visitor) noexcept {\n        try {\n            std::visit(std::forward&lt;Visitor&gt;(visitor), data);\n        } catch (...) {\n            \/\/ \u30a8\u30e9\u30fc\u30ed\u30b0\u8a18\u9332\u3084\u30d5\u30a9\u30fc\u30eb\u30d0\u30c3\u30af\u51e6\u7406\n        }\n    }\n};<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-17\">\u30b3\u30f3\u30d1\u30a4\u30e9\u5225\u306e\u52d5\u4f5c\u306e\u9055\u3044\u3068\u5bfe\u51e6\u6cd5<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u7570\u306a\u308b\u30b3\u30f3\u30d1\u30a4\u30e9\u3067\u306e\u52d5\u4f5c\u306e\u9055\u3044\u306b\u5bfe\u51e6\u3059\u308b\u65b9\u6cd5\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;type_traits&gt;\n\n\/\/ \u30b3\u30f3\u30d1\u30a4\u30e9\u4f9d\u5b58\u306e\u554f\u984c\u306b\u5bfe\u3059\u308b\u9632\u5fa1\u7684\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\n#ifdef _MSC_VER\n    \/\/ Visual Studio\u306e\u305f\u3081\u306e\u7279\u6b8a\u5316\n    template&lt;typename T&gt;\n    struct CustomTraits {\n        static constexpr bool is_trivially_destructible =\n            std::is_trivially_destructible_v&lt;T&gt;;\n    };\n#else\n    \/\/ \u305d\u306e\u4ed6\u306e\u30b3\u30f3\u30d1\u30a4\u30e9\u7528\n    template&lt;typename T&gt;\n    struct CustomTraits {\n        static constexpr bool is_trivially_destructible =\n            std::is_trivially_destructible&lt;T&gt;::value;\n    };\n#endif\n\n\/\/ \u30b3\u30f3\u30d1\u30a4\u30e9\u4e92\u63db\u6027\u3092\u8003\u616e\u3057\u305fvariant\u30e9\u30c3\u30d1\u30fc\ntemplate&lt;typename... Types&gt;\nclass PortableVariant {\n    std::variant&lt;Types...&gt; data;\n\npublic:\n    \/\/ \u30b3\u30f3\u30d1\u30a4\u30e9\u4f9d\u5b58\u306e\u554f\u984c\u3092\u56de\u907f\u3059\u308b\u30d8\u30eb\u30d1\u30fc\u95a2\u6570\n    template&lt;typename T&gt;\n    static constexpr bool is_valid_type() {\n        if constexpr (CustomTraits&lt;T&gt;::is_trivially_destructible) {\n            return true;\n        } else {\n            \/\/ \u975e\u30c8\u30ea\u30d3\u30a2\u30eb\u306a\u30c7\u30b9\u30c8\u30e9\u30af\u30bf\u3092\u6301\u3064\u578b\u306e\u7279\u5225\u51e6\u7406\n            return std::is_nothrow_destructible_v&lt;T&gt;;\n        }\n    }\n\n    \/\/ \u5b89\u5168\u306a\u578b\u30c1\u30a7\u30c3\u30af\n    template&lt;typename T&gt;\n    constexpr bool holds() const {\n        if constexpr (is_valid_type&lt;T&gt;()) {\n            return std::holds_alternative&lt;T&gt;(data);\n        }\n        return false;\n    }\n};<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5b9f\u88c5\u6642\u306e\u4e3b\u306a\u6ce8\u610f\u70b9\uff1a<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u30e1\u30e2\u30ea\u30a2\u30e9\u30a4\u30e1\u30f3\u30c8\u95a2\u9023<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7570\u306a\u308b\u30a2\u30e9\u30a4\u30e1\u30f3\u30c8\u8981\u4ef6\u3092\u6301\u3064\u578b\u306e\u7d44\u307f\u5408\u308f\u305b\u306b\u6ce8\u610f<\/li>\n\n\n\n<li>\u30d1\u30c7\u30a3\u30f3\u30b0\u306b\u3088\u308b\u30e1\u30e2\u30ea\u6d6a\u8cbb\u306e\u9632\u6b62<\/li>\n\n\n\n<li>\u30ad\u30e3\u30c3\u30b7\u30e5\u30e9\u30a4\u30f3\u306e\u8003\u616e<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u4f8b\u5916\u5b89\u5168\u6027<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u72b6\u614b\u306e\u4e00\u8cab\u6027\u7dad\u6301<\/li>\n\n\n\n<li>\u30ea\u30bd\u30fc\u30b9\u30ea\u30fc\u30af\u306e\u9632\u6b62<\/li>\n\n\n\n<li>\u30ed\u30fc\u30eb\u30d0\u30c3\u30af\u6a5f\u69cb\u306e\u5b9f\u88c5<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u30b3\u30f3\u30d1\u30a4\u30e9\u4e92\u63db\u6027<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u6a19\u6e96\u898f\u683c\u3078\u306e\u6e96\u62e0\u78ba\u8a8d<\/li>\n\n\n\n<li>\u30b3\u30f3\u30d1\u30a4\u30e9\u56fa\u6709\u306e\u62e1\u5f35\u6a5f\u80fd\u3078\u306e\u4f9d\u5b58\u56de\u907f<\/li>\n\n\n\n<li>\u30af\u30ed\u30b9\u30d7\u30e9\u30c3\u30c8\u30d5\u30a9\u30fc\u30e0\u5bfe\u5fdc<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u4e3b\u306a\u843d\u3068\u3057\u7a74\u3068\u5bfe\u51e6\u6cd5\uff1a<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u8aa4\u3063\u305f\u578b\u30a2\u30af\u30bb\u30b9<\/strong><\/li>\n<\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">   std::variant&lt;int, std::string&gt; v = 42;\n   \/\/ \u5371\u967a\uff1a\u4f8b\u5916\u306e\u53ef\u80fd\u6027\n   auto str = std::get&lt;std::string&gt;(v);\n\n   \/\/ \u5b89\u5168\uff1a\u578b\u30c1\u30a7\u30c3\u30af\u4ed8\u304d\u30a2\u30af\u30bb\u30b9\n   if (auto pval = std::get_if&lt;std::string&gt;(&amp;v)) {\n       \/\/ \u5b89\u5168\u306b\u6587\u5b57\u5217\u306b\u30a2\u30af\u30bb\u30b9\u53ef\u80fd\n   }<\/pre>\n\n\n\n<ol start=\"2\" class=\"wp-block-list\">\n<li><strong>\u672a\u521d\u671f\u5316\u30a2\u30af\u30bb\u30b9<\/strong><\/li>\n<\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">   std::variant&lt;std::monostate, int&gt; v;\n   \/\/ \u5b89\u5168\uff1a\u521d\u671f\u72b6\u614b\u306e\u30c1\u30a7\u30c3\u30af\n   if (!std::holds_alternative&lt;std::monostate&gt;(v)) {\n       \/\/ \u5024\u304c\u8a2d\u5b9a\u3055\u308c\u3066\u3044\u308b\u5834\u5408\u306e\u51e6\u7406\n   }<\/pre>\n\n\n\n<ol start=\"3\" class=\"wp-block-list\">\n<li><strong>\u518d\u5e30\u7684\u306a\u578b\u306e\u53d6\u308a\u6271\u3044<\/strong><\/li>\n<\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">   \/\/ \u554f\u984c\u306e\u3042\u308b\u518d\u5e30\u7684\u5b9a\u7fa9\n   struct Node {\n       std::variant&lt;int, Node&gt; value;  \/\/ \u30b3\u30f3\u30d1\u30a4\u30eb\u30a8\u30e9\u30fc\n   };\n\n   \/\/ \u6b63\u3057\u3044\u5b9f\u88c5\n   struct Node {\n       std::variant&lt;int, std::unique_ptr&lt;Node&gt;&gt; value;\n   };<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u308c\u3089\u306e\u6ce8\u610f\u70b9\u3092\u9069\u5207\u306b\u8003\u616e\u3059\u308b\u3053\u3068\u3067\u3001\u3088\u308a\u5b89\u5168\u3067\u4fdd\u5b88\u6027\u306e\u9ad8\u3044\u30b3\u30fc\u30c9\u3092\u5b9f\u88c5\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"i-18\">std::variant\u3092\u4f7f\u7528\u3057\u305f\u30b3\u30fc\u30c9\u306e\u4fdd\u5b88\u6027\u5411\u4e0a\u30c6\u30af\u30cb\u30c3\u30af<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-19\">\u53ef\u8aad\u6027\u306e\u9ad8\u3044visitor\u5b9f\u88c5\u30d1\u30bf\u30fc\u30f3<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">visitor\u30d1\u30bf\u30fc\u30f3\u3092\u52b9\u679c\u7684\u306b\u5b9f\u88c5\u3057\u3001\u30b3\u30fc\u30c9\u306e\u53ef\u8aad\u6027\u3092\u5411\u4e0a\u3055\u305b\u308b\u65b9\u6cd5\u3092\u898b\u3066\u3044\u304d\u307e\u3059\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;string&gt;\n#include &lt;iostream&gt;\n#include &lt;type_traits&gt;\n\n\/\/ 1. \u540d\u524d\u4ed8\u304dvisitor\u30af\u30e9\u30b9\u306e\u4f7f\u7528\nclass MessageProcessor {\npublic:\n    void operator()(const std::string&amp; msg) const {\n        std::cout &lt;&lt; \"\u6587\u5b57\u5217\u30e1\u30c3\u30bb\u30fc\u30b8: \" &lt;&lt; msg &lt;&lt; std::endl;\n    }\n\n    void operator()(int code) const {\n        std::cout &lt;&lt; \"\u6570\u5024\u30b3\u30fc\u30c9: \" &lt;&lt; code &lt;&lt; std::endl;\n    }\n\n    void operator()(const std::vector&lt;int&gt;&amp; data) const {\n        std::cout &lt;&lt; \"\u30c7\u30fc\u30bf\u914d\u5217\u30b5\u30a4\u30ba: \" &lt;&lt; data.size() &lt;&lt; std::endl;\n    }\n};\n\n\/\/ 2. \u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u7279\u6b8a\u5316\u3092\u4f7f\u7528\u3057\u305f\u53ef\u8aad\u6027\u306e\u9ad8\u3044\u5b9f\u88c5\ntemplate&lt;typename T&gt;\nstruct TypedVisitor {\n    static void process(const T&amp; value) {\n        std::cout &lt;&lt; \"\u672a\u77e5\u306e\u578b: \" &lt;&lt; typeid(T).name() &lt;&lt; std::endl;\n    }\n};\n\ntemplate&lt;&gt;\nstruct TypedVisitor&lt;int&gt; {\n    static void process(int value) {\n        std::cout &lt;&lt; \"\u6574\u6570\u5024: \" &lt;&lt; value &lt;&lt; std::endl;\n    }\n};\n\ntemplate&lt;&gt;\nstruct TypedVisitor&lt;std::string&gt; {\n    static void process(const std::string&amp; value) {\n        std::cout &lt;&lt; \"\u6587\u5b57\u5217: \" &lt;&lt; value &lt;&lt; std::endl;\n    }\n};\n\n\/\/ 3. \u7d99\u627f\u3092\u4f7f\u7528\u3057\u305f\u62e1\u5f35\u53ef\u80fd\u306avisitor\nclass BaseVisitor {\npublic:\n    virtual void visitInt(int value) = 0;\n    virtual void visitString(const std::string&amp; value) = 0;\n    virtual ~BaseVisitor() = default;\n};\n\nclass ConcreteVisitor : public BaseVisitor {\npublic:\n    void visitInt(int value) override {\n        std::cout &lt;&lt; \"\u6574\u6570\u51e6\u7406: \" &lt;&lt; value &lt;&lt; std::endl;\n    }\n\n    void visitString(const std::string&amp; value) override {\n        std::cout &lt;&lt; \"\u6587\u5b57\u5217\u51e6\u7406: \" &lt;&lt; value &lt;&lt; std::endl;\n    }\n};\n\n\/\/ visitor\u306e\u4f7f\u7528\u4f8b\nvoid demonstrate_visitors() {\n    std::variant&lt;int, std::string&gt; value = 42;\n\n    \/\/ \u540d\u524d\u4ed8\u304dvisitor\u306e\u4f7f\u7528\n    std::visit(MessageProcessor{}, value);\n\n    \/\/ \u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u7279\u6b8a\u5316\u306e\u4f7f\u7528\n    std::visit([](const auto&amp; v) {\n        TypedVisitor&lt;std::decay_t&lt;decltype(v)&gt;&gt;::process(v);\n    }, value);\n}<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-20\">\u30e6\u30cb\u30c3\u30c8\u30c6\u30b9\u30c8\u3067\u306estd::variant\u306e\u6271\u3044\u65b9<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">std::variant\u3092\u4f7f\u7528\u3057\u305f\u30b3\u30fc\u30c9\u3092\u52b9\u679c\u7684\u306b\u30c6\u30b9\u30c8\u3059\u308b\u65b9\u6cd5\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;cassert&gt;\n#include &lt;stdexcept&gt;\n\n\/\/ \u30c6\u30b9\u30c8\u5bfe\u8c61\u306e\u30af\u30e9\u30b9\nclass VariantProcessor {\n    std::variant&lt;int, std::string&gt; data;\n\npublic:\n    VariantProcessor(std::variant&lt;int, std::string&gt; initial) \n        : data(std::move(initial)) {}\n\n    bool is_numeric() const {\n        return std::holds_alternative&lt;int&gt;(data);\n    }\n\n    std::string to_string() const {\n        return std::visit([](const auto&amp; v) -&gt; std::string {\n            if constexpr (std::is_same_v&lt;std::decay_t&lt;decltype(v)&gt;, int&gt;) {\n                return std::to_string(v);\n            } else {\n                return v;\n            }\n        }, data);\n    }\n};\n\n\/\/ \u30c6\u30b9\u30c8\u30b1\u30fc\u30b9\u5b9f\u88c5\nclass VariantTests {\npublic:\n    static void run_all_tests() {\n        test_construction();\n        test_type_checking();\n        test_conversion();\n        test_edge_cases();\n    }\n\nprivate:\n    static void test_construction() {\n        \/\/ \u6574\u6570\u3067\u306e\u521d\u671f\u5316\u30c6\u30b9\u30c8\n        VariantProcessor proc1(42);\n        assert(proc1.is_numeric());\n        assert(proc1.to_string() == \"42\");\n\n        \/\/ \u6587\u5b57\u5217\u3067\u306e\u521d\u671f\u5316\u30c6\u30b9\u30c8\n        VariantProcessor proc2(std::string(\"test\"));\n        assert(!proc2.is_numeric());\n        assert(proc2.to_string() == \"test\");\n    }\n\n    static void test_type_checking() {\n        std::variant&lt;int, std::string&gt; v = 42;\n        assert(std::holds_alternative&lt;int&gt;(v));\n        assert(!std::holds_alternative&lt;std::string&gt;(v));\n\n        v = \"test\";\n        assert(!std::holds_alternative&lt;int&gt;(v));\n        assert(std::holds_alternative&lt;std::string&gt;(v));\n    }\n\n    static void test_conversion() {\n        VariantProcessor proc(42);\n        assert(proc.to_string() == \"42\");\n\n        VariantProcessor proc2(\"hello\");\n        assert(proc2.to_string() == \"hello\");\n    }\n\n    static void test_edge_cases() {\n        \/\/ \u7a7a\u6587\u5b57\u5217\u306e\u30c6\u30b9\u30c8\n        VariantProcessor proc1(std::string(\"\"));\n        assert(proc1.to_string().empty());\n\n        \/\/ \u6700\u5927\u5024\u306e\u30c6\u30b9\u30c8\n        VariantProcessor proc2(std::numeric_limits&lt;int&gt;::max());\n        assert(!proc2.to_string().empty());\n    }\n};\n\n\/\/ \u30e2\u30c3\u30af\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u4f8b\nclass MockVariantVisitor {\npublic:\n    void operator()(int value) {\n        last_int_value = value;\n        int_called = true;\n    }\n\n    void operator()(const std::string&amp; value) {\n        last_string_value = value;\n        string_called = true;\n    }\n\n    bool int_called = false;\n    bool string_called = false;\n    int last_int_value = 0;\n    std::string last_string_value;\n};<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u4fdd\u5b88\u6027\u3092\u5411\u4e0a\u3055\u305b\u308b\u305f\u3081\u306e\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\uff1a<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u578b\u306e\u5236\u7d04\u3068\u691c\u8a3c<\/strong><\/li>\n<\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">   template&lt;typename... Types&gt;\n   class ValidatedVariant {\n       static_assert((... &amp;&amp; !std::is_pointer_v&lt;Types&gt;),\n           \"\u30dd\u30a4\u30f3\u30bf\u578b\u306f\u4f7f\u7528\u3067\u304d\u307e\u305b\u3093\");\n\n       std::variant&lt;Types...&gt; data;\n\n   public:\n       template&lt;typename T&gt;\n       void set(T&amp;&amp; value) {\n           static_assert((... || std::is_same_v&lt;std::decay_t&lt;T&gt;, Types&gt;),\n               \"\u7121\u52b9\u306a\u578b\u3067\u3059\");\n           data = std::forward&lt;T&gt;(value);\n       }\n   };<\/pre>\n\n\n\n<ol start=\"2\" class=\"wp-block-list\">\n<li><strong>\u30a8\u30e9\u30fc\u30cf\u30f3\u30c9\u30ea\u30f3\u30b0\u306e\u6a19\u6e96\u5316<\/strong><\/li>\n<\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">   template&lt;typename... Types&gt;\n   class SafeVariant {\n       std::variant&lt;Types...&gt; data;\n\n   public:\n       template&lt;typename T&gt;\n       bool try_get(T&amp; out) noexcept {\n           if (auto* ptr = std::get_if&lt;T&gt;(&amp;data)) {\n               out = *ptr;\n               return true;\n           }\n           return false;\n       }\n\n       template&lt;typename T&gt;\n       T get_or(T&amp;&amp; default_value) const {\n           if (auto* ptr = std::get_if&lt;T&gt;(&amp;data)) {\n               return *ptr;\n           }\n           return std::forward&lt;T&gt;(default_value);\n       }\n   };<\/pre>\n\n\n\n<ol start=\"3\" class=\"wp-block-list\">\n<li><strong>\u30c9\u30ad\u30e5\u30e1\u30f3\u30c8\u5316\u3068\u547d\u540d\u898f\u5247<\/strong><\/li>\n<\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">   \/\/ \u660e\u78ba\u306a\u578b\u30a8\u30a4\u30ea\u30a2\u30b9\u306e\u4f7f\u7528\n   using MessageVariant = std::variant&lt;\n       std::string,    \/\/ \u30c6\u30ad\u30b9\u30c8\u30e1\u30c3\u30bb\u30fc\u30b8\n       int,           \/\/ \u30a8\u30e9\u30fc\u30b3\u30fc\u30c9\n       std::vector&lt;int&gt; \/\/ \u30c7\u30fc\u30bf\u30da\u30a4\u30ed\u30fc\u30c9\n   &gt;;\n\n   \/\/ \u610f\u56f3\u3092\u660e\u78ba\u306b\u3059\u308b\u578b\u540d\n   enum class MessageType { Text, Error, Data };\n\n   class DocumentedVariant {\n       MessageVariant content;\n       MessageType type;\n\n   public:\n       \/\/ \u578b\u5b89\u5168\u306a\u30d5\u30a1\u30af\u30c8\u30ea\u30e1\u30bd\u30c3\u30c9\n       static DocumentedVariant createTextMessage(std::string text);\n       static DocumentedVariant createErrorMessage(int code);\n       static DocumentedVariant createDataMessage(std::vector&lt;int&gt; data);\n   };<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u308c\u3089\u306e\u30c6\u30af\u30cb\u30c3\u30af\u3092\u7d44\u307f\u5408\u308f\u305b\u308b\u3053\u3068\u3067\u3001\u3088\u308a\u4fdd\u5b88\u6027\u304c\u9ad8\u304f\u3001\u30c6\u30b9\u30c8\u304c\u5bb9\u6613\u306a\u30b3\u30fc\u30c9\u3092\u5b9f\u73fe\u3067\u304d\u307e\u3059\u3002\u7279\u306b\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u660e\u78ba\u306a\u547d\u540d\u898f\u5247\u306e\u63a1\u7528<\/li>\n\n\n\n<li>\u9069\u5207\u306a\u5358\u4f53\u30c6\u30b9\u30c8\u306e\u5b9f\u88c5<\/li>\n\n\n\n<li>\u30a8\u30e9\u30fc\u30b1\u30fc\u30b9\u306e\u5305\u62ec\u7684\u306a\u51e6\u7406<\/li>\n\n\n\n<li>\u578b\u5b89\u5168\u6027\u306e\u78ba\u4fdd<\/li>\n\n\n\n<li>\u30b3\u30fc\u30c9\u306e\u81ea\u5df1\u6587\u66f8\u5316<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u308c\u3089\u306e\u8981\u7d20\u306f\u3001\u9577\u671f\u7684\u306a\u30b3\u30fc\u30c9\u306e\u4fdd\u5b88\u6027\u3092\u5927\u304d\u304f\u5411\u4e0a\u3055\u305b\u307e\u3059\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"i-21\">\u767a\u5c55\u7684\u306astd::variant\u6d3b\u7528\u30c6\u30af\u30cb\u30c3\u30af<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-22\">\u518d\u5e30\u7684\u306avisitor\u30d1\u30bf\u30fc\u30f3\u306e\u5b9f\u88c5\u65b9\u6cd5<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u8907\u96d1\u306a\u30c7\u30fc\u30bf\u69cb\u9020\u306b\u5bfe\u3059\u308b\u518d\u5e30\u7684\u306avisitor\u30d1\u30bf\u30fc\u30f3\u306e\u5b9f\u88c5\u4f8b\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;vector&gt;\n#include &lt;memory&gt;\n#include &lt;iostream&gt;\n\n\/\/ \u518d\u5e30\u7684\u306a\u30c7\u30fc\u30bf\u69cb\u9020\u306e\u5b9a\u7fa9\nstruct Node;\nusing NodePtr = std::shared_ptr&lt;Node&gt;;\nusing Value = std::variant&lt;int, std::string, std::vector&lt;NodePtr&gt;&gt;;\n\nstruct Node {\n    Value value;\n    explicit Node(Value v) : value(std::move(v)) {}\n};\n\n\/\/ \u518d\u5e30\u7684\u306avisitor\u57fa\u5e95\u30af\u30e9\u30b9\nclass RecursiveVisitor {\npublic:\n    virtual void visitInt(int value) = 0;\n    virtual void visitString(const std::string&amp; value) = 0;\n    virtual void visitNodeList(const std::vector&lt;NodePtr&gt;&amp; nodes) = 0;\n    virtual ~RecursiveVisitor() = default;\n};\n\n\/\/ \u5177\u4f53\u7684\u306avisitor\u5b9f\u88c5\nclass TreePrinter : public RecursiveVisitor {\n    int depth = 0;\n\n    void printIndent() const {\n        for (int i = 0; i &lt; depth; ++i) {\n            std::cout &lt;&lt; \"  \";\n        }\n    }\n\npublic:\n    void visitInt(int value) override {\n        printIndent();\n        std::cout &lt;&lt; \"\u6574\u6570: \" &lt;&lt; value &lt;&lt; std::endl;\n    }\n\n    void visitString(const std::string&amp; value) override {\n        printIndent();\n        std::cout &lt;&lt; \"\u6587\u5b57\u5217: \" &lt;&lt; value &lt;&lt; std::endl;\n    }\n\n    void visitNodeList(const std::vector&lt;NodePtr&gt;&amp; nodes) override {\n        printIndent();\n        std::cout &lt;&lt; \"\u30ce\u30fc\u30c9\u30ea\u30b9\u30c8:\" &lt;&lt; std::endl;\n        ++depth;\n        for (const auto&amp; node : nodes) {\n            std::visit([this](const auto&amp; value) {\n                using T = std::decay_t&lt;decltype(value)&gt;;\n                if constexpr (std::is_same_v&lt;T, int&gt;) {\n                    visitInt(value);\n                } else if constexpr (std::is_same_v&lt;T, std::string&gt;) {\n                    visitString(value);\n                } else if constexpr (std::is_same_v&lt;T, std::vector&lt;NodePtr&gt;&gt;) {\n                    visitNodeList(value);\n                }\n            }, node-&gt;value);\n        }\n        --depth;\n    }\n};\n\n\/\/ \u4f7f\u7528\u4f8b\nvoid demonstrate_recursive_visitor() {\n    auto leaf1 = std::make_shared&lt;Node&gt;(42);\n    auto leaf2 = std::make_shared&lt;Node&gt;(std::string(\"Hello\"));\n    auto parent = std::make_shared&lt;Node&gt;(std::vector&lt;NodePtr&gt;{leaf1, leaf2});\n\n    TreePrinter printer;\n    std::visit([&amp;printer](const auto&amp; value) {\n        using T = std::decay_t&lt;decltype(value)&gt;;\n        if constexpr (std::is_same_v&lt;T, std::vector&lt;NodePtr&gt;&gt;) {\n            printer.visitNodeList(value);\n        }\n    }, parent-&gt;value);\n}<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-23\">\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30e1\u30bf\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u3068\u306e\u7d44\u307f\u5408\u308f\u305b\u4f8b<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">std::variant\u3068\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30e1\u30bf\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u3092\u7d44\u307f\u5408\u308f\u305b\u305f\u9ad8\u5ea6\u306a\u5b9f\u88c5\u4f8b\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">#include &lt;variant&gt;\n#include &lt;type_traits&gt;\n#include &lt;tuple&gt;\n\n\/\/ \u578b\u30ea\u30b9\u30c8\u306e\u64cd\u4f5c\ntemplate&lt;typename... Ts&gt;\nstruct TypeList {};\n\n\/\/ \u578b\u30ea\u30b9\u30c8\u306e\u5909\u63db\ntemplate&lt;typename List&gt;\nstruct ToVariant;\n\ntemplate&lt;typename... Ts&gt;\nstruct ToVariant&lt;TypeList&lt;Ts...&gt;&gt; {\n    using type = std::variant&lt;Ts...&gt;;\n};\n\n\/\/ \u578b\u30d5\u30a3\u30eb\u30bf\u30ea\u30f3\u30b0\ntemplate&lt;typename T, typename Predicate&gt;\nstruct FilterType {\n    using type = std::conditional_t&lt;\n        Predicate::template apply&lt;T&gt;::value,\n        TypeList&lt;T&gt;,\n        TypeList&lt;&gt;\n    &gt;;\n};\n\n\/\/ \u518d\u5e30\u7684\u306a\u578b\u30d5\u30a3\u30eb\u30bf\u30ea\u30f3\u30b0\ntemplate&lt;typename List, typename Predicate&gt;\nstruct Filter;\n\ntemplate&lt;typename Predicate&gt;\nstruct Filter&lt;TypeList&lt;&gt;, Predicate&gt; {\n    using type = TypeList&lt;&gt;;\n};\n\ntemplate&lt;typename T, typename... Ts, typename Predicate&gt;\nstruct Filter&lt;TypeList&lt;T, Ts...&gt;, Predicate&gt; {\n    using filtered_head = typename FilterType&lt;T, Predicate&gt;::type;\n    using filtered_tail = typename Filter&lt;TypeList&lt;Ts...&gt;, Predicate&gt;::type;\n    using type = typename Concat&lt;filtered_head, filtered_tail&gt;::type;\n};\n\n\/\/ \u30ab\u30b9\u30bf\u30e0variant\u578b\u306e\u751f\u6210\ntemplate&lt;typename... Types&gt;\nclass EnhancedVariant {\n    using StorageType = std::variant&lt;Types...&gt;;\n    StorageType storage;\n\npublic:\n    \/\/ \u578b\u5236\u7d04\u30c1\u30a7\u30c3\u30af\n    template&lt;typename T&gt;\n    static constexpr bool is_valid_type = (std::is_same_v&lt;T, Types&gt; || ...);\n\n    \/\/ \u578b\u5b89\u5168\u306a\u4ee3\u5165\n    template&lt;typename T&gt;\n    void assign(T&amp;&amp; value) {\n        static_assert(is_valid_type&lt;std::decay_t&lt;T&gt;&gt;,\n            \"\u7121\u52b9\u306a\u578b\u3067\u3059\");\n        storage = std::forward&lt;T&gt;(value);\n    }\n\n    \/\/ \u578b\u5b89\u5168\u306a\u30a2\u30af\u30bb\u30b9\n    template&lt;typename T&gt;\n    const T* get_if() const {\n        static_assert(is_valid_type&lt;T&gt;,\n            \"\u7121\u52b9\u306a\u578b\u3067\u3059\");\n        return std::get_if&lt;T&gt;(&amp;storage);\n    }\n};\n\n\/\/ \u9ad8\u5ea6\u306a\u578b\u5909\u63db\u6a5f\u80fd\ntemplate&lt;typename... Types&gt;\nclass VariantConverter {\n    using VariantType = std::variant&lt;Types...&gt;;\n    VariantType value;\n\npublic:\n    explicit VariantConverter(VariantType v) : value(std::move(v)) {}\n\n    \/\/ \u578b\u306b\u5fdc\u3058\u305f\u5909\u63db\u3092\u5b9f\u884c\n    template&lt;typename T&gt;\n    auto convert() const {\n        return std::visit([](const auto&amp; v) -&gt; T {\n            if constexpr (std::is_convertible_v&lt;\n                std::decay_t&lt;decltype(v)&gt;, T&gt;) {\n                return static_cast&lt;T&gt;(v);\n            } else {\n                throw std::bad_variant_access();\n            }\n        }, value);\n    }\n};\n\n\/\/ \u8907\u5408\u7684\u306avariant\u64cd\u4f5c\u306e\u4f8b\ntemplate&lt;typename... Types&gt;\nclass VariantProcessor {\n    std::variant&lt;Types...&gt; data;\n\n    \/\/ \u578b\u30ea\u30b9\u30c8\u304b\u3089\u6761\u4ef6\u3092\u6e80\u305f\u3059\u578b\u3092\u62bd\u51fa\n    template&lt;template&lt;typename&gt; class Predicate&gt;\n    using FilteredTypes = typename Filter&lt;\n        TypeList&lt;Types...&gt;,\n        Predicate&lt;void&gt;\n    &gt;::type;\n\npublic:\n    \/\/ \u6570\u5024\u578b\u306e\u307f\u3092\u51e6\u7406\n    template&lt;typename Func&gt;\n    void process_numbers(Func&amp;&amp; func) {\n        using NumericTypes = FilteredTypes&lt;std::is_arithmetic&gt;;\n        std::visit([&amp;func](const auto&amp; value) {\n            using T = std::decay_t&lt;decltype(value)&gt;;\n            if constexpr (std::is_arithmetic_v&lt;T&gt;) {\n                func(value);\n            }\n        }, data);\n    }\n\n    \/\/ \u6587\u5b57\u5217\u578b\u306e\u307f\u3092\u51e6\u7406\n    template&lt;typename Func&gt;\n    void process_strings(Func&amp;&amp; func) {\n        using StringTypes = FilteredTypes&lt;std::is_convertible_to_string&gt;;\n        std::visit([&amp;func](const auto&amp; value) {\n            using T = std::decay_t&lt;decltype(value)&gt;;\n            if constexpr (std::is_convertible_v&lt;T, std::string&gt;) {\n                func(std::string(value));\n            }\n        }, data);\n    }\n};<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u308c\u3089\u306e\u767a\u5c55\u7684\u306a\u30c6\u30af\u30cb\u30c3\u30af\u3092\u6d3b\u7528\u3059\u308b\u3053\u3068\u3067\u3001\u4ee5\u4e0b\u306e\u3088\u3046\u306a\u9ad8\u5ea6\u306a\u6a5f\u80fd\u3092\u5b9f\u73fe\u3067\u304d\u307e\u3059\uff1a<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u578b\u5b89\u5168\u306a\u518d\u5e30\u7684\u30c7\u30fc\u30bf\u69cb\u9020<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8907\u96d1\u306a\u968e\u5c64\u69cb\u9020\u306e\u8868\u73fe<\/li>\n\n\n\n<li>\u578b\u5b89\u5168\u306a\u64cd\u4f5c\u306e\u4fdd\u8a3c<\/li>\n\n\n\n<li>\u52b9\u7387\u7684\u306a\u30e1\u30e2\u30ea\u7ba1\u7406<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u30e1\u30bf\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u306b\u3088\u308b\u578b\u64cd\u4f5c<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u6761\u4ef6\u306b\u57fa\u3065\u304f\u578b\u30d5\u30a3\u30eb\u30bf\u30ea\u30f3\u30b0<\/li>\n\n\n\n<li>\u578b\u5909\u63db\u306e\u81ea\u52d5\u5316<\/li>\n\n\n\n<li>\u30b3\u30f3\u30d1\u30a4\u30eb\u6642\u306e\u578b\u30c1\u30a7\u30c3\u30af<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>\u9ad8\u5ea6\u306a\u30d1\u30bf\u30fc\u30f3\u30de\u30c3\u30c1\u30f3\u30b0<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8907\u96d1\u306a\u6761\u4ef6\u5206\u5c90\u306e\u7c21\u7565\u5316<\/li>\n\n\n\n<li>\u578b\u306b\u57fa\u3065\u304f\u51e6\u7406\u306e\u5206\u96e2<\/li>\n\n\n\n<li>\u30b3\u30fc\u30c9\u306e\u53ef\u8aad\u6027\u5411\u4e0a<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u308c\u3089\u306e\u6280\u8853\u3092\u9069\u5207\u306b\u7d44\u307f\u5408\u308f\u305b\u308b\u3053\u3068\u3067\u3001\u3088\u308a\u67d4\u8edf\u3067\u4fdd\u5b88\u6027\u306e\u9ad8\u3044\u30b3\u30fc\u30c9\u3092\u5b9f\u73fe\u3067\u304d\u307e\u3059\u3002\u305f\u3060\u3057\u3001\u8907\u96d1\u306a\u5b9f\u88c5\u306f\u5fc5\u8981\u306a\u5834\u5408\u306b\u306e\u307f\u4f7f\u7528\u3057\u3001\u53ef\u80fd\u306a\u9650\u308a\u30b7\u30f3\u30d7\u30eb\u306a\u89e3\u6c7a\u7b56\u3092\u9078\u629e\u3059\u308b\u3053\u3068\u3092\u63a8\u5968\u3057\u307e\u3059\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Warning: Undefined array key &#8220;is_admin&#8221; 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