title: cannot convert ‘std::vector<double>*’ to ‘__gnu_cxx::__alloc_traits<std::allocator<double*>, double*>::value_type’ {aka ‘double*’}
body: <p>I can't convert the double to double here
  in main.h I have :</p>
  <pre><code>std::vector&lt;std::vector&lt;double&gt;&gt; *m_va;
  
  std::vector&lt;std::vector&lt;double&gt; &gt; *get_ptr() { return m_va; }
  </code></pre>
  <p>in main.cpp I want to have :</p>
  <pre><code>std::vector&lt;double *&gt; F(n);
  
  F[i] = this-&gt;get_ptr()[j].data();
  </code></pre>
  <p>but I got :
  cannot convert ‘std::vector<em>’ to ‘__gnu_cxx::__alloc_traitsstd::allocator&lt;double*, double</em>&gt;::value_type’ {aka ‘double*’}</p>