title: How to check if path is valid in boost::filesystem?
body: <p>I am setting a <code>boost::filesystem::path</code> from an edit field.  I notice that the constructor is happy to accept invalid characters for the filename.</p>
  
  <p>How can I use <code>boost::filesystem</code> to check if the <code>boost::filesystem::path</code> object represents a valid filename?</p>