1 files changed, 14 insertions, 0 deletions
diff --git a/prolog/problems/dcg/expr_3/en.py b/prolog/problems/dcg/expr_3/en.py
new file mode 100644
index 0000000..3f91977
--- /dev/null
+++ b/prolog/problems/dcg/expr_3/en.py
@@ -0,0 +1,14 @@
+id = 171
+name = 'expr/3'
+slug = 'arithmetic expressions with meaning'
+
+description = '''\
+<p>Write a DCG with the starting symbol <code>expr</code> for the language of arithmetic expressions consisting of numbers (without leading zeros), addition and multiplication. Subexpressions can be grouped using parentheses. The meaning of a word in this language is the numeric value of the represented arithmetic expression.</p>
+<p>Example words: <code>(1+2)*3</code>, <code>42*8*3</code>, <code>(2+1)*(3+4)</code>.</p>
+<pre>
+  ?- expr(N, ['(',2,'+',1,')','*','(',3,'+',4,')'], []).  % (2+1)*(3+4) = 21
+    N = 21.
+</pre>
+'''
+
+hint = {}