name = 'ancestor/2'
slug = 'the ancestor relation'

description = '''\
<p><code>ancestor(X, Y)</code>: <code>X</code> is an ancestor (parent, grandparent, …) of <code>Y</code>.</p>
<pre>
?- ancestor(patricia, X).
  X = john ;
  X = michael ;
  X = michelle.
</pre>'''

hint = {}