title: c++ : convert vector to tuple
body: <p>How can I convert std::vector to std::tuple ?
  I have </p>
  
  <pre><code>class T { };
  int cnt = 3;
  vector&lt;T*&gt; tv;
  for (int i = 0; i &lt; cnt; ++i) {
    tv.push_back(new T());
  }
  </code></pre>
  
  <p>I want to get</p>
  
  <pre><code>auto tp = std::tie(*tv[0], *tv[1], *tv[2]);
  </code></pre>
  
  <p>How can I get this tp ?
  If cnt is big enough, I can't write this tp manually.</p>
  
  <pre><code>  std::vector&lt;
    ConvConnection&lt;
    decltype(inputLayer),
    decltype(*C1[0]),
    decltype(*Conn1Opt[0]),
    RandomInitialization&lt;arma::mat&gt;,
    arma::mat
    &gt;* &gt; Conn1(6);
  
    for (size_t i = 0; i &lt; 6; ++i) {
      Conn1.push_back(new  ConvConnection&lt;
                      decltype(inputLayer),
                      decltype(*C1[0]),
                      decltype(*Conn1Opt[0]),
                      RandomInitialization&lt;arma::mat&gt;,
                      arma::mat
                      &gt;(inputLayer, *C1[i], *Conn1Opt[i], 5, 5));
    }
  </code></pre>
  
  <p>This is the code. Here is just 6, but I also need some vector whose size is over 100. I need to convert this vector to a tuple.</p>