diff --git a/doc/html/variant2.html b/doc/html/variant2.html
index bd19d78..bec6d59 100644
--- a/doc/html/variant2.html
+++ b/doc/html/variant2.html
@@ -2,22 +2,21 @@
 <html lang="en">
 <head>
 <meta charset="UTF-8">
-<!--[if IE]><meta http-equiv="X-UA-Compatible" content="IE=edge"><![endif]-->
+<meta http-equiv="X-UA-Compatible" content="IE=edge">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
-<meta name="generator" content="Asciidoctor 1.5.7">
+<meta name="generator" content="Asciidoctor 2.0.9">
 <meta name="author" content="Peter Dimov">
 <title>Boost.Variant2: A never valueless variant type</title>
 <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Open+Sans:300,300italic,400,400italic,600,600italic%7CNoto+Serif:400,400italic,700,700italic%7CDroid+Sans+Mono:400,700">
 <style>
-/* Asciidoctor default stylesheet | MIT License | http://asciidoctor.org */
-/* Uncomment @import statement below to use as custom stylesheet */
+/* Asciidoctor default stylesheet | MIT License | https://asciidoctor.org */
+/* Uncomment @import statement to use as custom stylesheet */
 /*@import "https://fonts.googleapis.com/css?family=Open+Sans:300,300italic,400,400italic,600,600italic%7CNoto+Serif:400,400italic,700,700italic%7CDroid+Sans+Mono:400,700";*/
-article,aside,details,figcaption,figure,footer,header,hgroup,main,nav,section,summary{display:block}
-audio,canvas,video{display:inline-block}
+article,aside,details,figcaption,figure,footer,header,hgroup,main,nav,section{display:block}
+audio,video{display:inline-block}
 audio:not([controls]){display:none;height:0}
-script{display:none!important}
 html{font-family:sans-serif;-ms-text-size-adjust:100%;-webkit-text-size-adjust:100%}
-a{background:transparent}
+a{background:none}
 a:focus{outline:thin dotted}
 a:active,a:hover{outline:0}
 h1{font-size:2em;margin:.67em 0}
@@ -70,7 +69,7 @@ select{width:100%}
 div,dl,dt,dd,ul,ol,li,h1,h2,h3,#toctitle,.sidebarblock>.content>.title,h4,h5,h6,pre,form,p,blockquote,th,td{margin:0;padding:0;direction:ltr}
 a{color:#2156a5;text-decoration:underline;line-height:inherit}
 a:hover,a:focus{color:#1d4b8f}
-a img{border:none}
+a img{border:0}
 p{font-family:inherit;font-weight:400;font-size:1em;line-height:1.6;margin-bottom:1.25em;text-rendering:optimizeLegibility}
 p aside{font-size:.875em;line-height:1.35;font-style:italic}
 h1,h2,h3,#toctitle,.sidebarblock>.content>.title,h4,h5,h6{font-family:"Open Sans","DejaVu Sans",sans-serif;font-weight:300;font-style:normal;color:#ba3925;text-rendering:optimizeLegibility;margin-top:1em;margin-bottom:.5em;line-height:1.0125em}
@@ -80,7 +79,7 @@ h2{font-size:1.6875em}
 h3,#toctitle,.sidebarblock>.content>.title{font-size:1.375em}
 h4,h5{font-size:1.125em}
 h6{font-size:1em}
-hr{border:solid #ddddd8;border-width:1px 0 0;clear:both;margin:1.25em 0 1.1875em;height:0}
+hr{border:solid #dddddf;border-width:1px 0 0;clear:both;margin:1.25em 0 1.1875em;height:0}
 em,i{font-style:italic;line-height:inherit}
 strong,b{font-weight:bold;line-height:inherit}
 small{font-size:60%;line-height:inherit}
@@ -111,20 +110,23 @@ table{background:#fff;margin-bottom:1.25em;border:solid 1px #dedede}
 table thead,table tfoot{background:#f7f8f7}
 table thead tr th,table thead tr td,table tfoot tr th,table tfoot tr td{padding:.5em .625em .625em;font-size:inherit;color:rgba(0,0,0,.8);text-align:left}
 table tr th,table tr td{padding:.5625em .625em;font-size:inherit;color:rgba(0,0,0,.8)}
-table tr.even,table tr.alt,table tr:nth-of-type(even){background:#f8f8f7}
+table tr.even,table tr.alt{background:#f8f8f7}
 table thead tr th,table tfoot tr th,table tbody tr td,table tr td,table tfoot tr td{display:table-cell;line-height:1.6}
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+:not(pre):not([class^=L])>code{font-size:.9375em;font-style:normal!important;letter-spacing:0;padding:.1em .5ex;word-spacing:-.15em;background:#f7f7f8;-webkit-border-radius:4px;border-radius:4px;line-height:1.45;text-rendering:optimizeSpeed;word-wrap:break-word}
+:not(pre)>code.nobreak{word-wrap:normal}
+:not(pre)>code.nowrap{white-space:nowrap}
+pre{color:rgba(0,0,0,.9);font-family:"Droid Sans Mono","DejaVu Sans Mono",monospace;line-height:1.45;text-rendering:optimizeSpeed}
+pre code,pre pre{color:inherit;font-size:inherit;line-height:inherit}
+pre>code{display:block}
+pre.nowrap,pre.nowrap pre{white-space:pre;word-wrap:normal}
 em em{font-style:normal}
 strong strong{font-weight:400}
 .keyseq{color:rgba(51,51,51,.8)}
-kbd{font-family:"Droid Sans Mono","DejaVu Sans Mono",monospace;display:inline-block;color:rgba(0,0,0,.8);font-size:.65em;line-height:1.45;background-color:#f7f7f7;border:1px solid #ccc;-webkit-border-radius:3px;border-radius:3px;-webkit-box-shadow:0 1px 0 rgba(0,0,0,.2),0 0 0 .1em white inset;box-shadow:0 1px 0 rgba(0,0,0,.2),0 0 0 .1em #fff inset;margin:0 .15em;padding:.2em .5em;vertical-align:middle;position:relative;top:-.1em;white-space:nowrap}
+kbd{font-family:"Droid Sans Mono","DejaVu Sans Mono",monospace;display:inline-block;color:rgba(0,0,0,.8);font-size:.65em;line-height:1.45;background:#f7f7f7;border:1px solid #ccc;-webkit-border-radius:3px;border-radius:3px;-webkit-box-shadow:0 1px 0 rgba(0,0,0,.2),0 0 0 .1em white inset;box-shadow:0 1px 0 rgba(0,0,0,.2),0 0 0 .1em #fff inset;margin:0 .15em;padding:.2em .5em;vertical-align:middle;position:relative;top:-.1em;white-space:nowrap}
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 .keyseq kbd:last-child{margin-right:0}
 .menuseq,.menuref{color:#000}
@@ -142,9 +144,9 @@ p a>code:hover{color:rgba(0,0,0,.9)}
 #content{margin-top:1.25em}
 #content::before{content:none}
 #header>h1:first-child{color:rgba(0,0,0,.85);margin-top:2.25rem;margin-bottom:0}
-#header>h1:first-child+#toc{margin-top:8px;border-top:1px solid #ddddd8}
-#header>h1:only-child,body.toc2 #header>h1:nth-last-child(2){border-bottom:1px solid #ddddd8;padding-bottom:8px}
-#header .details{border-bottom:1px solid #ddddd8;line-height:1.45;padding-top:.25em;padding-bottom:.25em;padding-left:.25em;color:rgba(0,0,0,.6);display:-ms-flexbox;display:-webkit-flex;display:flex;-ms-flex-flow:row wrap;-webkit-flex-flow:row wrap;flex-flow:row wrap}
+#header>h1:first-child+#toc{margin-top:8px;border-top:1px solid #dddddf}
+#header>h1:only-child,body.toc2 #header>h1:nth-last-child(2){border-bottom:1px solid #dddddf;padding-bottom:8px}
+#header .details{border-bottom:1px solid #dddddf;line-height:1.45;padding-top:.25em;padding-bottom:.25em;padding-left:.25em;color:rgba(0,0,0,.6);display:-ms-flexbox;display:-webkit-flex;display:flex;-ms-flex-flow:row wrap;-webkit-flex-flow:row wrap;flex-flow:row wrap}
 #header .details span:first-child{margin-left:-.125em}
 #header .details span.email a{color:rgba(0,0,0,.85)}
 #header .details br{display:none}
@@ -153,8 +155,8 @@ p a>code:hover{color:rgba(0,0,0,.9)}
 #header .details br+span#revremark::before{content:"\00a0|\00a0"}
 #header #revnumber{text-transform:capitalize}
 #header #revnumber::after{content:"\00a0"}
-#content>h1:first-child:not([class]){color:rgba(0,0,0,.85);border-bottom:1px solid #ddddd8;padding-bottom:8px;margin-top:0;padding-top:1rem;margin-bottom:1.25rem}
-#toc{border-bottom:1px solid #efefed;padding-bottom:.5em}
+#content>h1:first-child:not([class]){color:rgba(0,0,0,.85);border-bottom:1px solid #dddddf;padding-bottom:8px;margin-top:0;padding-top:1rem;margin-bottom:1.25rem}
+#toc{border-bottom:1px solid #e7e7e9;padding-bottom:.5em}
 #toc>ul{margin-left:.125em}
 #toc ul.sectlevel0>li>a{font-style:italic}
 #toc ul.sectlevel0 ul.sectlevel1{margin:.5em 0}
@@ -165,13 +167,13 @@ p a>code:hover{color:rgba(0,0,0,.9)}
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 @media screen and (min-width:768px){#toctitle{font-size:1.375em}
 body.toc2{padding-left:15em;padding-right:0}
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+#toc.toc2{margin-top:0!important;background:#f8f8f7;position:fixed;width:15em;left:0;top:0;border-right:1px solid #e7e7e9;border-top-width:0!important;border-bottom-width:0!important;z-index:1000;padding:1.25em 1em;height:100%;overflow:auto}
 #toc.toc2 #toctitle{margin-top:0;margin-bottom:.8rem;font-size:1.2em}
 #toc.toc2>ul{font-size:.9em;margin-bottom:0}
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 #toc.toc2 ul.sectlevel0 ul.sectlevel1{padding-left:0;margin-top:.5em;margin-bottom:.5em}
 body.toc2.toc-right{padding-left:0;padding-right:15em}
-body.toc2.toc-right #toc.toc2{border-right-width:0;border-left:1px solid #efefed;left:auto;right:0}}
+body.toc2.toc-right #toc.toc2{border-right-width:0;border-left:1px solid #e7e7e9;left:auto;right:0}}
 @media screen and (min-width:1280px){body.toc2{padding-left:20em;padding-right:0}
 #toc.toc2{width:20em}
 #toc.toc2 #toctitle{font-size:1.375em}
@@ -181,69 +183,70 @@ body.toc2.toc-right{padding-left:0;padding-right:20em}}
 #content #toc{border-style:solid;border-width:1px;border-color:#e0e0dc;margin-bottom:1.25em;padding:1.25em;background:#f8f8f7;-webkit-border-radius:4px;border-radius:4px}
 #content #toc>:first-child{margin-top:0}
 #content #toc>:last-child{margin-bottom:0}
-#footer{max-width:100%;background-color:rgba(0,0,0,.8);padding:1.25em}
+#footer{max-width:100%;background:rgba(0,0,0,.8);padding:1.25em}
 #footer-text{color:rgba(255,255,255,.8);line-height:1.44}
 #content{margin-bottom:.625em}
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-.sect1+.sect1{border-top:1px solid #efefed}
+.sect1+.sect1{border-top:1px solid #e7e7e9}
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@@ -479,55 +484,353 @@ body.book #toc,body.book #preamble,body.book h1.sect0,body.book .sect1>h2{page-b
 <h2 id="overview">Overview</h2>
 <div class="sectionbody">
 <div class="paragraph">
-<p>This library implements a type-safe discriminated union (variant) type,
-<code>variant&lt;T&#8230;&#8203;&gt;</code>, that almost conforms to the C++17 Standard&#8217;s
-<a href="http://en.cppreference.com/w/cpp/utility/variant"><code>std::variant&lt;T&#8230;&#8203;&gt;</code></a>. The
-main differences between the two are:</p>
-</div>
-<div class="ulist">
-<ul>
-<li>
-<p><code>variant&lt;T&#8230;&#8203;&gt;</code> does not have a valueless-by-exception state;</p>
-</li>
-<li>
-<p>A converting constructor from, e.g. <code>variant&lt;int, float&gt;</code> to
-<code>variant&lt;float, double, int&gt;</code> is provided as an extension;</p>
-</li>
-<li>
-<p>The reverse operation, going from <code>variant&lt;float, double, int&gt;</code> to
-<code>variant&lt;int, float&gt;</code> is provided as the member function <code>subset&lt;U&#8230;&#8203;&gt;</code>.
-(This operation can throw if the current state of the variant cannot be
-represented.)</p>
-</li>
-<li>
-<p><code>variant&lt;T&#8230;&#8203;&gt;</code> is not trivial when all contained types are trivial, as
-mandated by C++17.</p>
-</li>
-</ul>
+<p>This library implements a type-safe discriminated/tagged union type,
+<code>variant&lt;T&#8230;&#8203;&gt;</code>, that is API-compatible with the C&#43;&#43;17 Standard&#8217;s
+<a href="http://en.cppreference.com/w/cpp/utility/variant"><code>std::variant&lt;T&#8230;&#8203;&gt;</code></a>.</p>
 </div>
 <div class="paragraph">
-<p>To avoid the valueless-by-exception state, this implementation falls
-back to using double storage unless</p>
-</div>
-<div class="ulist">
-<ul>
-<li>
-<p>one of the alternatives is the type <code>monostate</code>,</p>
-</li>
-<li>
-<p>one of the alternatives has a nonthrowing default constructor, or</p>
-</li>
-<li>
-<p>all the contained types are nothrow move constructible.</p>
-</li>
-</ul>
+<p>A <code>variant&lt;T1, T2, &#8230;&#8203;, Tn&gt;</code> variable can hold a value of any of the
+types <code>T1</code>, <code>T2</code>, &#8230;&#8203;, <code>Tn</code>. For example,
+<code>variant&lt;int64_t, double, std::string&gt;</code> can hold an <code>int64_t</code> value, a
+<code>double</code> value, or a <code>string</code> value.</p>
 </div>
 <div class="paragraph">
-<p>If the first two bullets don&#8217;t hold, but the third does, the variant uses
-single storage, but <code>emplace</code> constructs a temporary and moves it into place
-if the construction of the object can throw. In case this is undesirable, one
-can force <code>emplace</code> into always constructing in-place by adding <code>monostate</code> as
-one of the alternatives.</p>
+<p>Such a type is sometimes called a "tagged union", because it&#8217;s roughly
+equivalent to</p>
+</div>
+<div class="listingblock">
+<div class="content">
+<pre class="highlight"><code>struct V
+{
+    enum tag { tag_int64_t, tag_double, tag_string };
+
+    tag tag_;
+
+    union
+    {
+        int64_t     i_;
+        double      d_;
+        std::string s_;
+    };
+};</code></pre>
+</div>
+</div>
+<div class="paragraph">
+<p>Variants can be used to represent dynamically-typed values. A configuration
+file of the form</p>
+</div>
+<div class="listingblock">
+<div class="content">
+<pre class="highlight"><code>server.host=test.example.com
+server.port=9174
+cache.max_load=0.7</code></pre>
+</div>
+</div>
+<div class="paragraph">
+<p>can be represented as <code>std::map&lt;std::string, variant&lt;int64_t, double,
+std::string&gt;&gt;</code>.</p>
+</div>
+<div class="paragraph">
+<p>Variants can also represent polymorphism. To take a classic example, a
+polymorphic collection of shapes:</p>
+</div>
+<div class="listingblock">
+<div class="content">
+<pre class="highlight"><code>#define _USE_MATH_DEFINES
+#include &lt;iostream&gt;
+#include &lt;vector&gt;
+#include &lt;memory&gt;
+#include &lt;cmath&gt;
+
+class Shape
+{
+public:
+
+    virtual ~Shape() = default;
+    virtual double area() const = 0;
+};
+
+class Rectangle: public Shape
+{
+private:
+
+    double width_, height_;
+
+public:
+
+    Rectangle( double width, double height ):
+        width_( width ), height_( height ) {}
+
+    virtual double area() const { return width_ * height_; }
+};
+
+class Circle: public Shape
+{
+private:
+
+    double radius_;
+
+public:
+
+    explicit Circle( double radius ): radius_( radius ) {}
+    virtual double area() const { return M_PI * radius_ * radius_; }
+};
+
+double total_area( std::vector&lt;std::unique_ptr&lt;Shape&gt;&gt; const &amp; v )
+{
+    double s = 0.0;
+
+    for( auto const&amp; p: v )
+    {
+        s += p-&gt;area();
+    }
+
+    return s;
+}
+
+int main()
+{
+    std::vector&lt;std::unique_ptr&lt;Shape&gt;&gt; v;
+
+    v.push_back( std::unique_ptr&lt;Shape&gt;( new Circle( 1.0 ) ) );
+    v.push_back( std::unique_ptr&lt;Shape&gt;( new Rectangle( 2.0, 3.0 ) ) );
+
+    std::cout &lt;&lt; "Total area: " &lt;&lt; total_area( v ) &lt;&lt; std::endl;
+}</code></pre>
+</div>
+</div>
+<div class="paragraph">
+<p>can instead be represented as a collection of <code>variant&lt;Rectangle, Circle&gt;</code>
+values. This requires the possible <code>Shape</code> types be known in advance, as is
+often the case. In return, we no longer need virtual functions, or to allocate
+the values on the heap with <code>new Rectangle</code> and <code>new Circle</code>:</p>
+</div>
+<div class="listingblock">
+<div class="content">
+<pre class="highlight"><code>#define _USE_MATH_DEFINES
+#include &lt;iostream&gt;
+#include &lt;vector&gt;
+#include &lt;cmath&gt;
+
+#include &lt;boost/variant2/variant.hpp&gt;
+using namespace boost::variant2;
+
+struct Rectangle
+{
+    double width_, height_;
+    double area() const { return width_ * height_; }
+};
+
+struct Circle
+{
+    double radius_;
+    double area() const { return M_PI * radius_ * radius_; }
+};
+
+double total_area( std::vector&lt;variant&lt;Rectangle, Circle&gt;&gt; const &amp; v )
+{
+    double s = 0.0;
+
+    for( auto const&amp; x: v )
+    {
+        s += visit( []( auto const&amp; y ){ return y.area(); }, x );
+    }
+
+    return s;
+}
+
+int main()
+{
+    std::vector&lt;variant&lt;Rectangle, Circle&gt;&gt; v;
+
+    v.push_back( Circle{ 1.0 } );
+    v.push_back( Rectangle{ 2.0, 3.0 } );
+
+    std::cout &lt;&lt; "Total area: " &lt;&lt; total_area( v ) &lt;&lt; std::endl;
+}</code></pre>
+</div>
+</div>
+<div class="paragraph">
+<p>If we look at the</p>
+</div>
+<div class="listingblock">
+<div class="content">
+<pre class="highlight"><code>    v.push_back( Circle{ 1.0 } );</code></pre>
+</div>
+</div>
+<div class="paragraph">
+<p>line, we can deduce that <code>variant&lt;Rectangle, Circle&gt;</code> can be (implicitly)
+constructed from <code>Circle</code> (and <code>Rectangle</code>), and indeed it can. It can also
+be assigned a <code>Circle</code> or a <code>Rectangle</code>:</p>
+</div>
+<div class="listingblock">
+<div class="content">
+<pre class="highlight"><code>variant&lt;Rectangle, Circle&gt; v = Circle{ 1.0 }; // v holds Circle
+v = Rectangle{ 2.0, 3.0 };                    // v now holds Rectangle</code></pre>
+</div>
+</div>
+<div class="paragraph">
+<p>If we try to construct <code>variant&lt;int, float&gt;</code> from something that is neither
+<code>int</code> nor <code>float</code>, say, <code>(short)1</code>, the behavior is "as if" the <code>variant</code> has
+declared two constructors,</p>
+</div>
+<div class="listingblock">
+<div class="content">
+<pre class="highlight"><code>variant::variant(int x);
+variant::variant(float x);</code></pre>
+</div>
+</div>
+<div class="paragraph">
+<p>and the standard overload resolution rules are used to pick the one that will
+be used. So <code>variant&lt;int, float&gt;((short)1)</code> will hold an <code>int</code>.</p>
+</div>
+<div class="paragraph">
+<p>Putting values into a <code>variant</code> is easy, but taking them out is necessarily a
+bit more convoluted. It&#8217;s not possible for <code>variant&lt;int, float&gt;</code> to define a
+member function <code>get() const</code>, because such a function will need its return
+type fixed at compile time, and whether the correct return type is <code>int</code> or
+<code>float</code> will only become known at run time.</p>
+</div>
+<div class="paragraph">
+<p>There are a few ways around that. First, there is the accessor member function</p>
+</div>
+<div class="listingblock">
+<div class="content">
+<pre class="highlight"><code>std::size_t variant::index() const noexcept;</code></pre>
+</div>
+</div>
+<div class="paragraph">
+<p>that returns the zero-based index of the current type. For <code>variant&lt;int,
+float&gt;</code>, it will return <code>0</code> for <code>int</code> and <code>1</code> for <code>float</code>.</p>
+</div>
+<div class="paragraph">
+<p>Once we have the index, we can use the free function <code>get&lt;N&gt;</code> to obtain the
+value. Since we&#8217;re passing the type index to <code>get</code>, it knows what to return.
+<code>get&lt;0&gt;(v)</code> will return <code>int</code>, and <code>get&lt;1&gt;(v)</code> will return <code>float</code>:</p>
+</div>
+<div class="listingblock">
+<div class="content">
+<pre class="highlight"><code>void f( variant&lt;int, float&gt; const&amp; v )
+{
+    switch( v.index() )
+    {
+    case 0:
+
+        // use get&lt;0&gt;(v)
+        break;
+
+    case 1:
+
+        // use get&lt;1&gt;(v)
+        break;
+
+    default:
+
+        assert(false); // never happens
+    }
+}</code></pre>
+</div>
+</div>
+<div class="paragraph">
+<p>If we call <code>get&lt;0&gt;(v)</code>, and <code>v.index()</code> is not currently <code>0</code>, an exception
+(of type <code>bad_variant_access</code>) will be thrown.</p>
+</div>
+<div class="paragraph">
+<p>An alternative approach is to use <code>get&lt;int&gt;(v)</code> or <code>get&lt;float&gt;(v)</code>. This
+works similarly.</p>
+</div>
+<div class="paragraph">
+<p>Another alternative that avoids the possibility of <code>bad_variant_access</code> is
+to use <code>get_if</code>. Instead of a reference to the contained value, it returns
+a pointer to it, returning <code>nullptr</code> to indicate type mismatch. <code>get_if</code>
+takes a pointer to the <code>variant</code>, so in our example we&#8217;ll use something along
+the following lines:</p>
+</div>
+<div class="listingblock">
+<div class="content">
+<pre class="highlight"><code>void f( variant&lt;int, float&gt; const&amp; v )
+{
+    if( int const * p = get_if&lt;int&gt;(&amp;v) )
+    {
+        // use *p
+    }
+    else if( float const * p = get_if&lt;float&gt;(&amp;v) )
+    {
+        // use *p
+    }
+    else
+    {
+        assert(false); // never happens
+    }
+}</code></pre>
+</div>
+</div>
+<div class="paragraph">
+<p>Last but not least, there&#8217;s <code>visit</code>. <code>visit(f, v)</code> calls the a function object
+<code>f</code> with the value contained in the <code>variant</code> <code>v</code> and returns the result. When
+<code>v</code> is <code>variant&lt;int, float&gt;</code>, it will call <code>f</code> with either an <code>int</code> or a
+<code>float</code>. The function object must be prepared to accept both.</p>
+</div>
+<div class="paragraph">
+<p>In practice, this can be achieved by having the function take a type that can
+be passed either <code>int</code> or <code>float</code>, such as <code>double</code>:</p>
+</div>
+<div class="listingblock">
+<div class="content">
+<pre class="highlight"><code>double f( double x ) { return x; }
+
+double g( variant&lt;int, float&gt; const&amp; v )
+{
+    return visit( f, v );
+}</code></pre>
+</div>
+</div>
+<div class="paragraph">
+<p>By using a function object with an overloaded <code>operator()</code>:</p>
+</div>
+<div class="listingblock">
+<div class="content">
+<pre class="highlight"><code>struct F
+{
+    void operator()(int x) const { /* use x */ }
+    void operator()(float x) const { /* use x */ }
+};
+
+void g( variant&lt;int, float&gt; const&amp; v )
+{
+    visit( F(), v );
+}</code></pre>
+</div>
+</div>
+<div class="paragraph">
+<p>Or by using a polymorphic lambda, as we did in our <code>Circle</code>/<code>Rectangle</code>
+example:</p>
+</div>
+<div class="listingblock">
+<div class="content">
+<pre class="highlight"><code>void g( variant&lt;int, float&gt; const&amp; v )
+{
+    visit( [&amp;]( auto const&amp; x ){ std::cout &lt;&lt; x &lt;&lt; std::endl; }, v );
+}</code></pre>
+</div>
+</div>
+<div class="paragraph">
+<p><code>visit</code> can also take more than one <code>variant</code>. <code>visit(f, v1, v2)</code> calls
+<code>f(x1, x2)</code>, where <code>x1</code> is the value contained in <code>v1</code> and <code>x2</code> is the value
+in <code>v2</code>.</p>
+</div>
+<div class="paragraph">
+<p>The default constructor of <code>variant</code> value-initializes the first type in
+the list. <code>variant&lt;int, float&gt;{}</code> holds <code>0</code> (of type <code>int</code>), and
+<code>variant&lt;float, int&gt;{}</code> holds <code>0.0f</code>.</p>
+</div>
+<div class="paragraph">
+<p>This is usually the desired behavior. However, in cases such as
+<code>variant&lt;std::mutex, std::recursive_mutex&gt;</code>, one might legitimately wish to
+avoid constructing a <code>std::mutex</code> by default. A provided type, <code>monostate</code>,
+can be used as the first type in those scenarios. <code>variant&lt;monostate,
+std::mutex, std::recursive_mutex&gt;</code> will default-construct a <code>monostate</code>,
+which is basically a no-op, as <code>monostate</code> is effectively an empty <code>struct</code>.</p>
 </div>
 </div>
 </div>
@@ -2189,12 +2492,13 @@ the <a href="http://www.boost.org/LICENSE_1_0.txt">Boost Software License, Versi
 </div>
 <div id="footer">
 <div id="footer-text">
-Last updated 2019-02-22 19:21:28 GTBST
+Last updated 2019-05-11 17:49:15 +0300
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+:not(pre):not([class^=L])>code { background: none; color: #600000; }
 
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