https://svn.boost.org/trac10/ticket/7960 <p> Current implementation of assignment and move assignment creates a <code>temp</code> variable if direct_assigner or direct_mover fail. We can avoid it, by checking if the type of variable to assign exactly matches one of the variant types. If it matches, we can do assign without creation of temporary variable. </p> <p> Here is some pseudo-code to show it: </p> <pre class="wiki"> template &lt;typename T&gt; void move_assign(T&amp;&amp; rhs) { // If direct T-to-T move assignment is not possible... detail::variant::direct_mover&lt;T&gt; direct_move(rhs); if (this-&gt;apply_visitor(direct_move) == false) { if (is_in_varaint_types&lt;T&gt;::value) { // ... but T is in varaint types, then destroy // content of storage and assign move_assigner visitor(*this, type_to_int&lt;T&gt;::value); visitor.internal_visit(rhs, 0); } else { // ...then convert rhs to variant and assign: // // While potentially inefficient, the following construction of a // variant allows T as any type convertible to one of the bounded // types without excessive code redundancy. // variant temp( detail::variant::move(rhs) ); variant_assign( detail::variant::move(temp) ); } } } </pre> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/7960 Trac 1.4.3 Antony Polukhin Wed, 02 Oct 2013 12:41:10 GMT https://svn.boost.org/trac10/ticket/7960#comment:4 https://svn.boost.org/trac10/ticket/7960#comment:4 <ul> <li><strong>status</strong> <span class="trac-field-old">new</span> → <span class="trac-field-new">closed</span> </li> <li><strong>resolution</strong> → <span class="trac-field-new">obsolete</span> </li> </ul> <p> Closing as the performance is OK now. </p> Ticket