href="date_time/doc/index.html">date_time</a> - Date-Time library from Jeff Garland.</li>
    <li><a href="filesystem/doc/index.htm">filesystem</a> - Portable paths, 
    iteration over directories, and other useful filesystem operations, from 
    Beman Dawes.</li>
    <li><a href="optional/doc/optional.html">optional</a> - Discriminated-union 
    wrapper for optional values, from Fernando Cacciola.</li>
    <li><a href="timer/index.html">timer</a> - Event timer,
        progress timer, and progress displ