Merge branch 'master' of 192.168.15.97:codeq-problems

1 files changed, 70 insertions, 3 deletions

diff --git a/prolog/problems/family_relations/cousin_2/en.py b/prolog/problems/family_relations/cousin_2/en.py
index 4ca9c87..a5627ee 100644
--- a/prolog/problems/family_relations/cousin_2/en.py
+++ b/prolog/problems/family_relations/cousin_2/en.py
@@ -2,11 +2,78 @@ name = 'cousin/2'
 slug = 'the cousin relation'
 
 description = '''\
-<p><code>cousin(X, Y)</code>: <code>X</code> is a cousin (male or female) of <code>Y</code>.</p>
+<p><code>cousin(X, Y)</code>: <code>X</code> is a cousin of <code>Y</code>.</p>
 <pre>
 ?- cousin(andrew, X).
   X = vanessa ;
   X = patricia.
-</pre>'''
+</pre>
+<p><a target="_blank" href="[%@resource famrel.svg%]">Family trees</a> are
+described with predicates <code>parent/2</code>, <code>male/1</code>, and
+<code>female/1</code>.</p>
+'''
+
+plan = ['''\
+<p>Perhaps you can make use of the solution to one of the previous exercises?</p>
+<p><img src="[%@resource Prolog_cousin_01.svg%]" alt="I have a child, my sibling also has a child..." /></p>
+<p>But of course it's also possible to solve without any of the previous solutions...</p>
+''', '''\
+<p>If <code>PX</code> is a parent of <code>X</code> and
+<code>PY</code> is a parent of <code>Y</code> and if
+<code>PX</code> and <code>PY</code> are siblings,
+then <code>X</code> is a cousin to <code>Y</code>.</p>
+''', '''\
+<p><img src="[%@resource Prolog_cousin_03.svg%]" alt="I have a child, my sibling has a child, these two children
+are therefore..." /></p>
+''']
+
+hint = {
+    'gender_is_irrelevant': '''\
+<p>Is gender really important?</p>
+''',
+
+    'gender_is_irrelevant_markup': '''\
+<p>Is this necessary?</p>
+''',
+
+    'precedence_fail': '''\
+<p>Did you mix up the precedence of operators <em>or</em> & <em>and</em>?</p>
+<p>Operator <em>and</em> has higher precedence than operator <em>or</em>.
+If you wish to change that you can always use the brackets.</p>
+''',
+
+    'cousin_vs_sibling': '''\
+<p>How can a cousin <code>X</code> at the same time also be a sibling of <code>Y</code>?
+Did you perhaps forget that the parents of <code>X</code> and <code>Y</code> should not be the same?
+(Be careful: if both a mother and a father are listed in the database, then prolog could find them as two
+<em>different</em> parents, which is logically absolutely correct.)</p>
+<p><img src="[%@resource Prolog_cousin_04.svg%]" /></p>
+''',
+
+    'cousin_to_oneself': '''\
+<p>How can someone be a cousin to him- or herself?
+Perhaps <code>X</code> and <code>Y</code> have the same parent?</p>
+<p><img src="[%@resource Prolog_cousin_04.svg%]" /></p>
+<p>Try this query: <code>?- cousin(X, X).</code></p>
+''',
+
+    'cousin_need_not_be_parent': '''\
+<p>A cousin doesn't need to have children...</p>
+''',
+
+    'predicate_always_false': '''\
+<p>It seems your predicate is <em>always</em> "false". Did you give it the correct name,
+or is it perhaps misspelled?</p>
+<p>If the name is correct, check whether something else is misspelled, perhaps there is a full stop instead of
+a comma or vice versa, or maybe you typed a variable name in lowercase?</p>
+<p>It is, of course, also possible that your conditions are too restrictive, or even impossible to satisfy
+(as would be, for example, the condition that <code>X</code> is both a parent and a sister of <code>Y</code>, or
+something similarly impossible).</p>
+''',
+
+#     'interesting_tidbit': '''\
+# <p>Zanimivost: nalogo bi lahko rešil tudi z uporabo rešitve za relacijo "sister".
+# Teta je namreč sestra od starša od <code>Y</code>.</p>
+# ''',
+}
 
-hint = {}