title: Boost.Program_Options: When <bool> is specified as a command-line option, what are valid command-line parameters?
body: <p>Given the following simple use of Boost.Program_Options:</p>
  
  <pre><code>boost::program_options::options_description options("Options");
  
  options.add_options()
  
      ("my_bool_flag,b", boost::program_options::value&lt;bool&gt;(), "Sample boolean switch)")
  
      ;
  </code></pre>
  
  <p>... what command-line arguments will evaluate to <code>false</code>, and what to <code>true</code>?</p>
  
  <p>(I.e., assume the program is named "foo", and executed on the command line as:
  <code>foo -b ?</code>
  ... with the question mark a placeholder for some other text: What are all possible text options that will properly evaluate to <code>false</code>, and what to <code>true</code>?)</p>