2 files changed, 23 insertions, 0 deletions
diff --git a/prolog/problems/dcg/paren_3/common.py b/prolog/problems/dcg/paren_3/common.py
new file mode 100644
index 0000000..cf7c439
--- /dev/null
+++ b/prolog/problems/dcg/paren_3/common.py
@@ -0,0 +1,10 @@
+id = 169
+group = 'dcg'
+number = 76
+visible = True
+facts = None
+
+solution = '''\
+paren(0) --> [].
+paren(D) --> ['('], paren(D1), [')'], paren(D2), { D1 >= D2, D is D1 + 1 ; D1 < D2 , D is D2 }.
+'''
diff --git a/prolog/problems/dcg/paren_3/en.py b/prolog/problems/dcg/paren_3/en.py
new file mode 100644
index 0000000..f4d4c3b
--- /dev/null
+++ b/prolog/problems/dcg/paren_3/en.py
@@ -0,0 +1,13 @@
+id = 169
+name = 'paren/3'
+slug = 'properly nested parens with meaning'
+
+description = '''\
+<p>Write a DCG with the starting symbol <code>paren</code> for the language of properly nested sequences of parentheses. The meaning of a word in this language is the maximum depth of the nested parentheses.</p>
+<pre>
+  ?- paren(D, ['(','(',')',')','(',')'], []).  % (())()
+    D = 2.
+</pre>
+'''
+
+hint = {}