   <TT>type <A name="solution">solution</A></TT>
    </DT>
    <DD>
      <P>The type of concrete solutions. Usually a tuple or a vector of integers.
      </P>
    </DD>

    <DT>
      <TT>type <A name="space">space</A></TT>
    </DT>
    <DD>
      <P>The type of constraint spaces. Always <A href="space.html"><TT>Space.space</TT></A>.
      </P>
    </DD>

    <DT>
      <TT><A name="root">root</A></TT>
    </DT>
    <DD><P>The root space, that is, a fresh constraint space where constraints have been pos