 notably not part of an instance&#39;s value.  Exposing other
non-value aspects of <code>Equatable</code> types is discouraged, and any
that <em>are</em> exposed should be explicitly pointed out in
documentation.</p>

<p><strong>Equality is an equivalence relation</strong></p>

<ul><li><code>x == x</code> is <code>true</code></li><li><code>x == y</code> implies <code>y == x</code></li><li><code>x == y</code> and <code>y == z</code> implies <code>x == z</code></li></ul>

<p><strong>Inequality is the inverse 