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    <p><strong>This is a self answer I came up with as a variant of the answer from Kerrek SB</strong></p> <p>It is possible to make a trait that extracts <code>std::vector</code> from <code>std::vector&lt;int&gt;</code> and exposes it as <code>::type</code> via a trait. Yes, this solution is nearly identical to Kerrek's, but to me the use syntax is more aesthetic, putting the template parameters after <code>::type</code>.</p> <pre><code>template &lt;typename T, typename ...&gt; struct retemplate { typedef T type; }; template &lt;template &lt;typename ...&gt; class Tmpl, typename ...T&gt; struct retemplate&lt;Tmpl&lt;T...&gt;&gt; { template &lt;typename ...AR&gt; using type=Tmpl&lt;AR...&gt; ; }; </code></pre> <p>with this you actually get <code>retemplate&lt;T&lt;A,B,C&gt;&gt;::type</code> equal to the template <code>T</code></p> <p>example use:</p> <pre><code>typedef std::vector&lt;int&gt; intvec; typedef retemplate&lt;intvec&gt;::type&lt;double&gt; doublevec; </code></pre> <p>or to expose the container type </p> <pre><code>typedef std::vector&lt;int&gt; intv; template &lt;typename ...T&gt; using vector_T= retemplate&lt;intv&gt;::type&lt;T...&gt; ; </code></pre> <p>Note that when using this in template context, an extra <code>template</code> is required just after <code>::</code>, like this: (elaborating on the comment from Xeo)</p> <pre><code>template &lt;typename T&gt; typename retemplate&lt;T&gt;::template type&lt;double&gt; containedDouble(T&amp; a) { decltype(containedDouble(a)) out; for (auto &amp;i : a) out.push_back(i); return out; } </code></pre> <p>What that does is to take an object of type <code>T1&lt;T2&gt;</code> and copy its content into a <code>T1&lt;double&gt;</code>. For example with <code>T1==std::vector</code> and <code>T2==int</code>. </p>
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    1. POtemplate metaprogramming: (trait for?) dissecting a specified template into types T<T2,T3 N,T4, ...>
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    1. USJohan Lundberg
    1. USJohan Lundberg
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    1. COThe calling snytax gets *slightly* ugly inside template code, though: `typename retemplate<intv>::template type<T...>`.
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    2. COThis is nice. I haven't quite got used to the new `using`s yet :-)
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    3. CO@Xeo: Why do you have to say `template`? There's no dependent name there, is there -- `intv` is an actual type.
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