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POcan a type tuple be unpacked later?
 

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  1. POcan a type tuple be unpacked later?
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    <p>I have a tuple of types encoded as</p> <pre><code>template&lt;class... T&gt;struct packed; </code></pre> <p>I want to unpack it later like</p> <pre><code>template&lt;class T&gt;struct unpack; template&lt;class... T&gt; struct unpack&lt;packed&lt;T...&gt;&gt;{ //how to define the unpacked type here? }; </code></pre> <p>So that, I can use it as</p> <pre><code>template&lt;class Packed&gt; struct foo : unpack&lt;Packed&gt;::type...{}; </code></pre> <p>Note, I do not want to unpack the elements of the tuple immediately like</p> <pre><code>template&lt;class... T&gt; struct unpack&lt;packed&lt;T...&gt;&gt; : T...{}; template&lt;class Packed&gt; struct foo: unpack&lt;Packed&gt;{}; </code></pre> <p>I am interested to have elements of the tuple 'packed' to be direct base classes of 'foo' instead of indirect base classes via 'unack'. Also the elements of the type tuple are distinct non-primitive and non-final types.</p> <p>To make the example more detailed,</p> <pre><code>template&lt;class T, T... Values&gt; struct variadic_values{}; template&lt;class T,T From,class Encode,T To&gt; struct value_gen; template&lt;class T, T From, T... Values, T To&gt; struct value_gen&lt;T,From,variadic_values&lt;T,Values...&gt;,To&gt; { using type = typename value_gen&lt;T,From+1,variadic_values&lt;T,Values...,From&gt;,To&gt;::type; }; template&lt;class T,T From,T... Values&gt; struct value_gen&lt;T,From,variadic_values&lt;T,Values...&gt;,From&gt; { using type = variadic_values&lt;T,Values...&gt;; }; template&lt;class T, T From,T To&gt; using values = typename value_gen&lt;T,From,variadic_values&lt;T&gt;,To&gt;::type; template&lt;unsigned Idx,class T&gt; struct node{}; template&lt;class Idx,class... Ts&gt; struct unpack; template&lt;unsigned... Idx,class...Ts&gt; struct unpack&lt;variadic_values&lt;unsigned,Idx...&gt;,Ts...&gt; : node&lt;Idx,Ts&gt;...{}; template&lt;class... Ts&gt; class foo : unpack&lt;values&lt;unsigned,0,sizeof...(ts)&gt;,Ts...&gt;{}; </code></pre> <p>What I am interested to have is that <code>foo</code> should be directly derived from <code>node</code>s</p>
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    1. COIt's not quite the same question, but I think some of the solutions to http://stackoverflow.com/questions/7858817/unpacking-a-tuple-to-call-a-matching-function-pointer would also work for this.
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    2. COI had gone though the solution before, but failed to convert it to a solution whet types are unpacked one by one rather than at a time. See comment on @HighCommander4
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