title: OStringStream and Namespaces Issue C++
body: <p>so I wanted to convert an integer into a string but using itoa isn't standard so through my research I figured the best way to do it would be to use OStringStream. Here's some pseudo-code:</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include &lt;cmath&gt;
  #include &lt;cstdlib&gt;
  
  
  std::string plusMinus(int x) {
  
      std::ostringstream x_str;
      // more code here obviously
  
  }
  
  int main(int argc, const char * argv[])
  {
      // some cin/cout functions here
  }
  </code></pre>
  
  <p>I get an error on the "std::ostringstream line: "Implicit instantiation of undefined template". What does this mean? I've tried putting "using namespace std;" at the top but it has no effect.</p>