title: How do I fix multiple declaration and multiple initialization errors?
body: <p>Sample 1></p>
  
  <pre><code>namespace Exercise {
      int ivar = 0;
  }
  
  int ivar = 0;    
  using Exercise::ivar; // &lt;&lt;== error
  </code></pre>
  
  <p>error C2874: using-declaration causes a multiple declaration of 'Exercise::ivar'    </p>
  
  <p>Sample 2></p>
  
  <pre><code>namespace Exercise {
      double dvar = 0;
  }
  
  int main(int argc, char* argv[])
  {   
      using Exercise::dvar;
  
      double dvar = 3.1416; // &lt;&lt;== error
  }
  
  error C2374: 'Exercise::dvar' : redefinition; multiple initialization
  </code></pre>
  
  <p>I have difficulties to understand these errors. can someone give me a little detail?</p>