title: error: `boost' has not been declared
body: <p>I'm trying to use boost libraries in my C++ application. I'm trying to compile it using g++ with different options.e.g <code>g++ -I /usr/include/boost/filesystem/ -o test.out test.cpp</code> however it always prompt  <code>error: 'boost' has not been declared</code>.  </p>
  
  <p>And here is my code:</p>
  
  <pre><code>#include &lt;fstream&gt;
  #include &lt;iostream&gt;
  #include &lt;string&gt;
  #include &lt;vector&gt;
  #include &lt;boost/filesystem.hpp&gt;
  using namespace std;
  int main (){
      string line;
      string fileName = "Read.txt";
      ifstream file;
      string str; 
      file.open(fileName.c_str());
      cout &lt;&lt; "Hello, world!\n";
      vector&lt;string&gt;  fileLines;
  
      fileLines.clear();
      while (getline(file, str))
      {
          fileLines.push_back(line);
      }
      cout &lt;&lt; "Total Line count:"&lt;&lt;fileLines.size()&lt;&lt;endl;
      fileLines.clear();
      cout &lt;&lt; "Total Line count:"&lt;&lt;fileLines.size()&lt;&lt;endl;
      boost::filesystem::path p("/tmp/foo.txt");
  
  
      return 0;
  }
  </code></pre>
  
  <p>I will be glad if you help me to fix this.</p>
  
  <p>P.S. I'm compiling my application in Centos 4.7 and It contains Boost version 1.32 according to <code>/usr/include/boost/version.hpp</code></p>
  
  <p><strong>Update:</strong></p>
  
  <p>I also commented boost instruction, but there is some problem with includes: <code>boost/filesystem.hpp: No such file or directory</code>.</p>