an_comparable&lt;T&gt;</a></code>. This
    rule also applies for <code><a href=
    "#less_than_comparable2">less_than_comparable&lt;T, U&gt;</a></code> and
    <code><a href="#partially_ordered2">partially_ordered&lt;T,
    U&gt;</a></code> with respect to the ordering of all <code>T</code> and
    <code>U</code> values, and for both versions of <code><a href=
    "#equivalent1">equivalent&lt;&gt;</a></code>. The solution for <code><a
    href="#equivalent1">equivalent&lt;&gt;</a></code> is to write a cus