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POtemplate 'using' declaration not working
 

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    <p>I have the following little test application, where I'm trying to employ a <em>template using</em> declaration.</p> <p>However, it doesn't compile. (I'm using gcc 4.6.1)</p> <blockquote> <p>src/main.cpp:36:3: error: expected unqualified-id before ‘using’</p> </blockquote> <ul> <li>Is my <em>using</em> declaration valid c++?</li> <li>Is it possible to create a template alias without specifying a type for one of the template parameters?</li> <li>Is it possible to create a template alias with a variadic template?</li> </ul> <p>Any insight greatly appreciated!</p> <pre><code>#include &lt;iostream&gt; #include &lt;utility&gt; template&lt;typename F, typename... Args&gt; struct invoke; // specialisation of invoke for 1 parameter template&lt;typename F, typename A0&gt; struct invoke&lt;F, A0&gt; { invoke(F&amp; f_, A0&amp;&amp; a0_) : _f(f_) , _a0(std::move(a0_)) {} void operator()() { _f(_a0); } F _f; A0 _a0; }; template&lt;typename F&gt; struct traits; // fwd declaration for handler struct handler; // specialisation of traits for handler template&lt;&gt; struct traits&lt;handler&gt; { template&lt;class F, typename... Args&gt; using call_t = invoke&lt;F, Args...&gt;; // line 36 }; template&lt;typename F&gt; struct do_it { template&lt;typename... Args&gt; void operator()(F&amp; _f, Args... args) { // create an object of the type declared in traits, and call it typename traits&lt;F&gt;::template call_t&lt;F, Args...&gt; func(_f, std::forward&lt;Args&gt;(args)...); func(); } }; struct handler { void operator()(int i) { std::cout &lt;&lt; i &lt;&lt; std::endl; } }; int main() { handler h; do_it&lt;handler&gt; d; d(h, 4); return 0; } </code></pre>
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