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    <p>While saying "the compiler can reserve", why rely on it? And what about automatic detection of move semantics? And what about all that repeating of the container name with the <code>begin</code>s and <code>end</code>s?</p> <p>Wouldn't you want something, you know, simpler?</p> <p>(Scroll down to <code>main</code> for the punchline)</p> <pre><code>#include &lt;type_traits&gt; #include &lt;vector&gt; #include &lt;iterator&gt; #include &lt;iostream&gt; template&lt;typename C,typename=void&gt; struct can_reserve: std::false_type {}; template&lt;typename T, typename A&gt; struct can_reserve&lt;std::vector&lt;T,A&gt;,void&gt;: std::true_type {}; template&lt;int n&gt; struct secret_enum { enum class type {}; }; template&lt;int n&gt; using SecretEnum = typename secret_enum&lt;n&gt;::type; template&lt;bool b, int override_num=1&gt; using EnableFuncIf = typename std::enable_if&lt; b, SecretEnum&lt;override_num&gt; &gt;::type; template&lt;bool b, int override_num=1&gt; using DisableFuncIf = EnableFuncIf&lt; !b, -override_num &gt;; template&lt;typename C, EnableFuncIf&lt; can_reserve&lt;C&gt;::value &gt;... &gt; void try_reserve( C&amp; c, std::size_t n ) { c.reserve(n); } template&lt;typename C, DisableFuncIf&lt; can_reserve&lt;C&gt;::value &gt;... &gt; void try_reserve( C&amp; c, std::size_t ) { } // do nothing template&lt;typename C,typename=void&gt; struct has_size_method:std::false_type {}; template&lt;typename C&gt; struct has_size_method&lt;C, typename std::enable_if&lt;std::is_same&lt; decltype( std::declval&lt;C&gt;().size() ), decltype( std::declval&lt;C&gt;().size() ) &gt;::value&gt;::type&gt;:std::true_type {}; namespace adl_aux { using std::begin; using std::end; template&lt;typename C&gt; auto adl_begin(C&amp;&amp;c)-&gt;decltype( begin(std::forward&lt;C&gt;(c)) ); template&lt;typename C&gt; auto adl_end(C&amp;&amp;c)-&gt;decltype( end(std::forward&lt;C&gt;(c)) ); } template&lt;typename C&gt; struct iterable_traits { typedef decltype( adl_aux::adl_begin(std::declval&lt;C&amp;&gt;()) ) iterator; typedef decltype( adl_aux::adl_begin(std::declval&lt;C const&amp;&gt;()) ) const_iterator; }; template&lt;typename C&gt; using Iterator = typename iterable_traits&lt;C&gt;::iterator; template&lt;typename C&gt; using ConstIterator = typename iterable_traits&lt;C&gt;::const_iterator; template&lt;typename I&gt; using IteratorCategory = typename std::iterator_traits&lt;I&gt;::iterator_category; template&lt;typename C, EnableFuncIf&lt; has_size_method&lt;C&gt;::value, 1&gt;... &gt; std::size_t size_at_least( C&amp;&amp; c ) { return c.size(); } template&lt;typename C, EnableFuncIf&lt; !has_size_method&lt;C&gt;::value &amp;&amp; std::is_base_of&lt; std::random_access_iterator_tag, IteratorCategory&lt;Iterator&lt;C&gt;&gt; &gt;::value, 2&gt;... &gt; std::size_t size_at_least( C&amp;&amp; c ) { using std::begin; using std::end; return end(c)-begin(c); }; template&lt;typename C, EnableFuncIf&lt; !has_size_method&lt;C&gt;::value &amp;&amp; !std::is_base_of&lt; std::random_access_iterator_tag, IteratorCategory&lt;Iterator&lt;C&gt;&gt; &gt;::value, 3&gt;... &gt; std::size_t size_at_least( C&amp;&amp; c ) { return 0; }; template &lt; typename It &gt; auto try_make_move_iterator(It i, std::true_type) -&gt; decltype(make_move_iterator(i)) { return make_move_iterator(i); } template &lt; typename It &gt; It try_make_move_iterator(It i, ...) { return i; } #include &lt;iostream&gt; template&lt;typename C1, typename C2&gt; C1&amp;&amp; append_containers( C1&amp;&amp; c1, C2&amp;&amp; c2 ) { using std::begin; using std::end; try_reserve( c1, size_at_least(c1) + size_at_least(c2) ); using is_rvref = std::is_rvalue_reference&lt;C2&amp;&amp;&gt;; c1.insert( end(c1), try_make_move_iterator(begin(c2), is_rvref{}), try_make_move_iterator(end(c2), is_rvref{}) ); return std::forward&lt;C1&gt;(c1); } struct append_infix_op {} append; template&lt;typename LHS&gt; struct append_on_right_op { LHS lhs; template&lt;typename RHS&gt; LHS&amp;&amp; operator=( RHS&amp;&amp; rhs ) { return append_containers( std::forward&lt;LHS&gt;(lhs), std::forward&lt;RHS&gt;(rhs) ); } }; template&lt;typename LHS&gt; append_on_right_op&lt;LHS&gt; operator+( LHS&amp;&amp; lhs, append_infix_op ) { return { std::forward&lt;LHS&gt;(lhs) }; } template&lt;typename LHS,typename RHS&gt; typename std::remove_reference&lt;LHS&gt;::type operator+( append_on_right_op&lt;LHS&gt;&amp;&amp; lhs, RHS&amp;&amp; rhs ) { typename std::decay&lt;LHS&gt;::type retval = std::forward&lt;LHS&gt;(lhs.lhs); return append_containers( std::move(retval), std::forward&lt;RHS&gt;(rhs) ); } template&lt;typename C&gt; void print_container( C&amp;&amp; c ) { for( auto&amp;&amp; x:c ) std::cout &lt;&lt; x &lt;&lt; ","; std::cout &lt;&lt; "\n"; }; int main() { std::vector&lt;int&gt; a = {0,1,2}; std::vector&lt;int&gt; b = {3,4,5}; print_container(a); print_container(b); a +append= b; const int arr[] = {6,7,8}; a +append= arr; print_container(a); print_container(b); std::vector&lt;double&gt; d = ( std::vector&lt;double&gt;{-3.14, -2, -1} +append= a ); print_container(d); std::vector&lt;double&gt; c = std::move(d) +append+ a; print_container(c); print_container(d); std::vector&lt;double&gt; e = c +append+ std::move(a); print_container(e); print_container(a); } </code></pre> <p><a href="https://ideone.com/WDBRF5">hehe</a>.</p> <p>Now with move-data-from-rhs, append-array-to-container, append forward_list-to-container, move-container-from-lhs, thanks to @DyP's help.</p> <p>Note that the above does not compile in clang thanks to the <code>EnableFunctionIf&lt;&gt;...</code> technique. In clang <a href="http://coliru.stacked-crooked.com/view?id=2aed6b92fe683bdc51dcb77e1fffdf60-bb452bed83d06e87c370fcabced7e96d">this workaround</a> works.</p>
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    1. POAppending a vector to a vector
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    1. USYakk - Adam Nevraumont
    1. USYakk - Adam Nevraumont
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    1. COI think you can simplify this, e.g. [the `try_reserve` part](http://coliru.stacked-crooked.com/view?id=4ff26889e8134023a0f2d2dd6962b8c7-c59112800dca6ae4674520521ddfe536)
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    2. COWhere do you use `size_at_least`? (I can only see declaration/definition, but no call..)
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    3. COOnly added the ["insert-by-move"](http://coliru.stacked-crooked.com/view?id=924c7f07cebeea9d727f1df6746d435e-c59112800dca6ae4674520521ddfe536)
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