2 files changed, 25 insertions, 0 deletions
diff --git a/prolog/problems/lists/dup_2/common.py b/prolog/problems/lists/dup_2/common.py
new file mode 100644
index 0000000..37a0842
--- /dev/null
+++ b/prolog/problems/lists/dup_2/common.py
@@ -0,0 +1,11 @@
+id = 110
+group = 'lists'
+number = 17
+visible = True
+facts = None
+
+solution = '''\
+dup([], []).
+dup([H|T], [H,H|TT]) :-
+  dup(T, TT).
+'''
diff --git a/prolog/problems/lists/dup_2/en.py b/prolog/problems/lists/dup_2/en.py
new file mode 100644
index 0000000..d6aef71
--- /dev/null
+++ b/prolog/problems/lists/dup_2/en.py
@@ -0,0 +1,14 @@
+id = 110
+name = 'dup/2'
+slug = 'duplicate the elements of a list'
+
+description = '''\
+<p><code>dup(L1, L2)</code>: the list <code>L2</code> is obtained from <code>L1</code> by duplicating every element.</p>
+<pre>
+  ?- dup([1,2], X).
+    X = [1,1,2,2].
+  ?- dup([1,2,3], X).
+    X = [1,1,2,2,3,3].
+</pre>'''
+
+hint = {}