prolog/problems/family_relations/sister_2/en.py


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

description = '''\
<p><code>sister(X, Y)</code>: <code>X</code> is a sister of <code>Y</code>.</p>
<pre>
?- sister(vanessa, X).
  X = patricia.
</pre>'''

hint = {
    'x_y_must_be_different': '''\
<p>What if <code>X</code> and <code>Y</code> are the same person? Try the
following query:</p>
<pre>
?- sister(sally, Y).
</pre>
''',
}