title: "vector" was not declared in this scope
body: <p>I got this error ,,"vector" was not declared in this scope'' for the following code when I separate in *h and *cpp a file
  This is the main.cpp:</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include &lt;math.h&gt;
  #include &lt;vector&gt;
  #include "functia.h"
  
  using namespace std;
  
  int main()
   {
    vector&lt;double&gt; s(3);
    double b= 4;
    fun(s, b);
    cout&lt;&lt;s[0]&lt;&lt;endl;
    double c= 9;
    fun(s, c);
    cout&lt;&lt;s[0];
  
    }
  </code></pre>
  
  <p>functia.h:</p>
  
  <pre><code> void fun(vector&lt;double&gt; &amp; rS, double a)
   {
     rS[0] = a + 3;
     rS[1] = 4;
     rS[2] = 5;
   }
  </code></pre>
  
  <p>functia.cpp:</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include &lt;math.h&gt;
  #include&lt;vector&gt;
  
  using namespace std;
  
  
  void fun(vector&lt;double&gt; &amp;, double );
  </code></pre>