Merge branch 'master' of 192.168.15.97:codeq-problems

1 files changed, 53 insertions, 2 deletions

diff --git a/prolog/problems/family_relations/father_2/en.py b/prolog/problems/family_relations/father_2/en.py
index b37c666..f1a9040 100644
--- a/prolog/problems/family_relations/father_2/en.py
+++ b/prolog/problems/family_relations/father_2/en.py
@@ -9,6 +9,57 @@ description = '''\
 ?- father(aleksander, X).
   X = luana ;
   X = daniela.
-</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>
+'''
 
-hint = {}
+plan = [
+    '''\
+<p><img src="[%@resource Prolog_father_01.svg%]" alt="A father is male and has a child." /></p>''',
+    '''\
+<p><img src="[%@resource Prolog_father_02.svg%]" alt="Father X is a parent of Y and is male." /></p>''',
+    '''\
+<p>If <code>X</code> is male and <code>X</code> is parent to <code>Y</code>,
+then <code>X</code> is a father of <code>Y</code>.</p>'''
+]
+
+hint = {
+    'or_instead_of_and': '''\
+<p>Did you perhaps use a semicolon (that represents logical OR) instead of a comma (logical AND)?</p>
+''',
+
+    'or_instead_of_and_two_rules': '''\
+<p>Did you perhaps write two rules: one for gender and one for parenthood?
+Be careful: this is understood as one <em>or</em> the other, not as one <em>and</em> the other!</p>
+''',
+
+    'x_must_be_male': '''\
+<p>A father is usually male.</p>
+<p><img src="[%@resource Prolog_father_03.svg%]" /></p>
+''',
+
+    'x_must_be_parent': '''\
+<p>A father is supposed to have at least one child... so he's a parent of somebody.</p>
+<p><img src="[%@resource Prolog_father_04.svg%]" /></p>
+''',
+
+    'y_can_be_of_any_gender': '''\
+<p><code>Y</code> can be of any gender.</p>
+''',
+
+    'y_need_not_be_parent': '''\
+<p><code>Y</code> 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>
+''',
+}