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POC++11 variadic template template parameters
 

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    <p>Keeping the old question. See below for resolution. It is probably something simple, but still. I have the following C++11 code fragment:</p> <pre><code>#include &lt;vector&gt; template &lt;typename... Ts&gt; struct typelist { }; template &lt;typename T&gt; struct EventContainer { typedef T Type; /// TODO. Ring buffer std::vector&lt;T&gt; container; void push(const T&amp; t) { EventContainer&lt;T&gt;::container.push_back(t); } virtual ~EventContainer() { } }; template &lt;template &lt;typename...&gt; class TL&gt; class EventStorage: public EventContainer&lt;Ts&gt;... { }; class Event1 { }; class Event2 { }; typedef typelist&lt;Event1,Event2&gt; Events12; int main() { EventStorage&lt;Events12&gt; ev; return 0; } </code></pre> <p>How can I make <code>EventStorage</code> inherit <code>EventContainer</code> templeted with each of the types in the <code>typelist</code>. I could do it with Loki:: library, but I want to use C++11 with variadic templates. Thank you.</p> <p>Resolution1: Fixing <code>EventStorage</code> template template issue. This will make <code>EventStorage</code>, multiple inherit all <code>EventContainer</code> templated with each type of <code>Ts</code>.</p> <pre><code>template &lt;typename...&gt; class EventStorage { }; template &lt;typename... Ts&gt; class EventStorage &lt; typelist&lt;Ts...&gt; &gt;: public EventContainer&lt;Ts&gt;... { }; </code></pre> <p>Now I have compile time error, on the following <code>main()</code>:</p> <pre><code>int main() { EventStorage&lt;Events12&gt; ev; Event1 ev1; ev.push(ev1); return 0; } In function ‘int main()’: error: request for member ‘push’ is ambiguous error: candidates are: void EventContainer&lt;T&gt;::push(const T&amp;) [with T = Event2] error: void EventContainer&lt;T&gt;::push(const T&amp;) [with T = Event1] </code></pre> <p>Why the compiler is confused? After all I push with specific type. GCC 4.6.1 here.</p> <p>Resolution2: As @Matthieu M. suggested I can present a forwarding method int <code>EventStorage</code>, but at a cost of one extra functin call:</p> <pre><code>template &lt;typename T&gt; void push(const T&amp; t) { EventContainer&lt;T&gt;::push(t); } </code></pre> <p>According to Alexandrescu, the compiler will optimize this forward call as long as parameters are references. Now the question is officially closed :)</p>
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